Optimizing Tomato Tolerance to Herbicides: Harnessing Biochar Herbicide Protection Pods for Enhanced Weed Control - Te Ming Tseng Evaluation of Plant Hormones and Other Seed Treatments to Reduce Injury Caused by Preemergent Herbicides on Direct-seeded Turnips and Collard Greens - Matthew Cutulle Flaming, Cultivation, and Handweeding Weed Control in Organic Carrot Production Systems with Different Fertilizer Types - Peter Dittmar Tolerance of Peppermint to Herbicides Applied Post-Harvest - Stephen Meyers Developing a Biobased, Compostable Mulch that Crops Grow Through - Samuel Wortman Evaluating Application Approaches for Enhancing the Weed Suppression Effectiveness and Crop-Safety of Preemergence Herbicides in Vegetable Plasticulture Production - Ramdas Kanissery
Weed control is a significant challenge in tomato production, often resulting in considerable yield losses and compromised fruit quality. Common weeds in tomato cultivation, such as nutsedges, annual grasses, and Palmer amaranth, exacerbate this issue. With limited effective weed control options available, there's a critical need for an integrated approach that can alleviate weed pressure while safeguarding crop yield and quality. One promising solution is the utilization of biochar herbicide protection pods (HPPs). In our greenhouse trial, we evaluated the efficacy of HPPs in enhancing tomato tolerance to S-metolachlor and metribuzin herbicides. By incorporating activated carbon within the HPPs to shield crop plants from soil-active herbicides, which they marginally tolerate, we aimed to improve weed management effectiveness. Tomato seeds were encapsulated within four distinct HPPs: DFBC Cornstarch, DFBC Selvol, RHBC Cornstarch, and RHBC Selvol. Control tomato seeds without biochar were also included. Treatments were applied to tomato seedlings at the 2-3 leaf stage with S-metolachlor (1681.28 g/ha) or metribuzin (1120.85 g/ha), with visual injury evaluations conducted at 7, 14, and 21 days after application (DAA). Dry mass measurements were taken at 21 DAA, with an untreated control included for comparison. In the presence of metribuzin, three biochar treatments exhibited injury levels of around 70%, compared to a higher injury rate of 79% in the treatment without biochar. However, there was no significant difference in dry mass. Conversely, no discernible injury differences were noted among treatments with S-metolachlor, yet three biochar treatments demonstrated substantial enhancements in dry biomass. Specifically, treatments with biochar recorded notable increases in dry mass compared to those without biochar, indicating a 28 to 35% boost in biomass. These preliminary findings highlight the potential of biochar HPPs in enhancing crop health, yield, and weed management efficacy in tomato farming.
Poor competitive ability and limited herbicide options make weed management of Brassica crops difficult. Growers often adopt the use of transplants, which is less efficient in terms of time, material, and labor when compared with direct seeding, resulting in higher prices per unit. Seed treatment with protective compounds could decrease crop injury from preemergent (PRE) herbicides making it profitable to direct-seed Brassica plants for production. Research was conducted to evaluate the ability of three candidate safeners [24-epibrassinolide, melatonin, and ascorbic acid (AsA)] to reduce injury caused by four herbicides (S-metolachlor, pyroxasulfone, halosulfuron, and mesotrione) applied PRE on the collard green cultivar Top Bunch and turnip cultivar Purple Top White Globe. Two independent greenhouse trials were conducted at the Clemson University Coastal Research and Education Center in Charleston, SC. Visual injury of the treated plants was evaluated weekly and dry mass was collected 21 days after treatment. Seed treatment did not reduce injury efficiently caused by pyroxasulfone, halosulfuron, and mesotrione; all doses were lethal for both crops. However, collard seeds treated using melatonin and AsA had 66% and 54% less injury caused by S-metolachlor at 514 g⋅ha–1 a.i., respectively. On turnips, melatonin was the only treatment that reduced the S-metolachlor damage on seedlings, with 43% less injury than untreated seedlings. Plant injury and plant weight correlated significantly for both Brassica crops. The reduction in injury caused by S-metolachlor when seeds were treated with melatonin and AsA validated those compounds’ protective ability. Seed treatment with melatonin could be combined with PRE applications of S-metolachlor to overcome the low weed competitive ability of these species early in the season.
Weed management is a common weed management practice in organic weed control, however, this practice is expensive. Other integrated weed management practice could include flaming and cultivation. The study objective is to investigate flaming, cultivation, and hand weeding to develop an integrated weed control program in organic carrot. The study was conducted in an organic certified field at the North Florida Research and Education Center Suwanee County, Live Oak, FL. Treatments were a factorial design with 5 weed management programs and 2 fertilizer types. Weed management treatments were (1) flaming preseeding weekly cultivation, (2) flaming preseeding weekly cultivation 1 handweeding event, (3) flaming preseeding flaming preemergence weekly cultivation (4) flaming preseeding flaming preemergence weekly cultivation 1 handweeding event, (5) flaming preseeding flaming preemergence weekly cultivation 2 handweeding events. Fertilizer treatments were pelleted poultry litter and 50% feather meal 50% poultry litter. Carrot ‘Uppercut’ were seeded on December 3, 2020 and were harvested on May 3, 2021. Eight rows of carrot were planted on a 0.9 m bed top. Fertilizer was applied immediately after seeding. Weeds were counted by species in two 0.5 m2 quadrats prior to each basket weeder cultivation between the rows. Carrots were cultivated 6 times before the carrot were too large and would be injured. Fertilizer type were not different for weed counts at all dates. Cutleaf evening primrose (Oenothera laciniata) was the only weed species in the plots from the beginning of the trial through harvest. The inclusion of flaming preplant and preemergence delayed the emergence of cutleaf evening primrose, however at 6 weeks after planting all the treatments were similar. Mid-season weed species included henbit (Lamium amplexicaule) and common chickweed (Stellaria media), however, these weed species were not present late-season. Purple toadflax (Linaria purpurea) and old world diamond flower (Oldenlandia corymbosa) were the most common weed species late-season. Single handweeding had excellent control early-season, but two handweeding events controlled both the cool and warm season weeds. Early season weed control should include flaming. Between row weed management was best with cultivation. Handweeding is necessary for late season weed control when flaming and cultivation are not available.
After harvest, peppermint is vulnerable to weed interference due to the loss of crop canopy. However, few herbicides are registered for use during this critical time in the production cycle. In response to this, we conducted research trials in 2023 at two commercial peppermint production fields in Indiana (North Judson and Fair Oaks) to determine peppermint response to preemergence and postemergence herbicides. Preemergence herbicide treatments included Zidua (1.84 fl oz/a), Optogen (3 fl oz/a), Spartan (4 fl oz/a), Chateau EZ (4 fl oz/a), Dual Magnum (1 pt/a), Fierce EZ (10 fl oz/a), and Tenacity (3 fl oz/a). Postemergence herbicide treatments included Basagran (2 pt/a), Reviton (2 fl oz/a), Tough (24 fl oz/a), Sharpen (2 fl oz/a), Anthem Flex (4.5 fl oz/a), Aim (1 fl oz/a), and Tough (24 fl oz/a) plus either Optogen (1.5 fl oz/a), Tenacity (1.5 fl oz/a), or Basagran (2 pt/a). Visible crop injury on a scale of 0 (no injury) to 100% (crop death), as well as crop height, was recorded every other week after treatment. Eight weeks after treatment, the greatest injury was observed was from the Group 14 herbicides: Reviton (81-84%), Sharpen (81-88%), and Aim (33-54%). Injury from Group 27 herbicides, Optogen and Tenacity, was more severe at Fair Oaks (63% and 64%, respectively) than at North Judson (28% and 12%, respectively). However, combining a half rate of these herbicides with Tough greatly increased crop injury at both locations (>73%). Injury from Chateau EZ and Fierce EZ differed by location; injury was lower at North Judson (13% and 7%, respectively) than at Fair Oaks (42% and 55%, respectively). Crop injury from Zidua, Dual Magnum, Spartan, Basagran, and Tough plus Basagran were similar to, or less than, Tough applied alone (the registered grower standard). Peppermint height and end-of-season aboveground biomass followed similar trends.
Plastic mulch films and geotextile landscape fabrics are not compatible with specialty crops grown at high densities with narrow in-row spacing. As a result, many growers resort to hand weeding these specialty crops, including leafy greens, carrots, and matted-row strawberries. Our objective was to develop and test value-added weed barrier mulches designed specifically for these crops to grow on and root through. We have conducted 13 trials across 3 crops (lettuce, carrot, and strawberry) and 3 years to evaluate 9 different biobased, compostable weed barrier mulches (BCMs) that include polylactic acid (PLA) resin. The BCMs tested varied in weight basis and material composition including: 1) PLA-only (80, 120, and 180 g/m2), 2) PLA embedded organic fertilizers (soybean meal and composted turkey litter; 150 and 210 g/m2), and 3) PLA paper (105 and 210 g/m2). The BCMs are installed in the field like a typical mulch film roll but are then covered with a 1 to 2.5 cm layer of compost (or other weed-free media) and crop seeds. Data was collected to evaluate effects of BCMs on weed density, soil nitrogen availability, moisture, and temperature, microbial abundance, and crop establishment, yield, and quality. Across all crops and site-years, BCMs reduced weed emergence by 80% to 97% compared to bare soil, and weed suppression was best in PLA paper. The BCMs immobilized some available soil nitrogen and embedded fertilizers in the BCM did not affect this outcome. In carrot, BCMs increased mycorrhizal fungi abundance by up to 59% compared to bare soil. In strawberry, BCMs increased crop canopy area by up to 51%. Yields were usually not different between BCMs and bare soil because weeds were removed weekly after counting. However, poor seedling establishment on BCMs due to heavy rainfall after planting in 2022 reduced carrot yield by 13% and lettuce yield by 20%. To address this issue, lettuce in 2023 was planted in two shallow seed furrows filled with compost on the BCM (instead of broadcast planting across the entire BCM bed top as in previous years). Lettuce establishment in the furrows was two times greater than in bare soil due to improved tilth and reduced erosion, and yield was not different from bare soil. Volumetric soil moisture in BCM compost seed furrows was 27.1% compared to 35.7% in bare soil, highlighting differences in texture and the importance of irrigation in the BCM system during establishment.
Preemergence herbicide application under plastic mulch is an effective strategy for managing weeds in vegetable plasticulture production. However, applying herbicides under plastic mulch in raised beds carries the inherent risk of crop phytotoxicity. This underscores the importance of exploring crop-safe methods for herbicide application in beds covered with plastic mulch. The study aimed to evaluate the efficacy of preemergence herbicide S-metolachlor alone or in combination with super absorbent polymer, soil binding agent, or compost in effectively controlling weeds in plastic mulched tomato beds without impacting the crops. During trials, I and II, preemergence S-metolachlor was applied either as blanket sprays or in combination with super absorbent polymer, soil binding agent, and compost on raised beds before installing plastic mulch. Results from trial II showed that S-metolachlor soil binding agent and S-metolachlor compost mix suppressed weed density by over 85% and 68%, respectively. Similarly, treatments including S-metolachlor alone, S-metolachlor super absorbent polymer, S-metolachlor soil binding agent, and S-metolachlor compost led to a reduction in weed biomass by over 50% compared to the non-treated control. Importantly, these treatments did not significantly impact tomato crop vigor and chlorophyll content during trials I and II, nor did they affect tomato crop biomass and yield. In conclusion, utilizing preemergence S-metolachlor along with different application approaches tested shows promise for controlling tough weeds such as nutsedge in tomato plasticulture beds.
Evaluating Efficacy of Organic Herbicides on Common Weed Species - Carly Strauser Evaluating Fall Cover Crops for Enhanced Soil Properties and No-Till Weed Suppression in Chickpea Production in Virginia - Zelalem Mersha Impact of Cover Crops and Herbicides on Early Season Weed Control and Sweetpotato Storage Root Yield. - Richard Noel Torres Effects of Row-middle Cover Crops on Strawberry Plasticulture Production - Jeanine Arana Palmer Amaranth and Waterhemp in the Pacific Northwest: Glyphosate Resistance Confirmation and Implications for Crop Production - Albert Adjesiwor Mesotrione and Simazine-Based Tank-Mixes for Late-Season Control of Doveweed in Bermudagrass Turf - Pawel Petelewicz Simulation-Based Nozzle Density Optimization for Maximized Efficacy of a Machine-Vision Weed Control System for Applications in Turfgrass Settings - Pawel Petelewicz Implementing Digital Multispectral 3D Scanning Technology for Rapid Assessment of Hemp (Cannabis sativa L.) Weed Competitive Traits - Tyler Campbell Farmer Experiences with Soil Tarping Across South Dakota - Hannah Voye
Soil tarping is a weed control method used by innovative farmers across the globe. Strategies used by farmers vary in terms of tarping material, time of application, length of time soil is covered, and the production goal. Solarization is a tarping technique that uses clear greenhouse plastic to harness light and energy from the sun to germinate weed seeds in the soil and exhaust the weed seed bank prior to a growing season. Occultation is another tarping technique that uses opaque tarps to warm the soil and stop light from germinating weed seeds or encouraging plant growth beneath the tarp. Researchers have taken an interest in exploring solarization and occultation impacts on weed suppression and soil health. During the 2023 and 2024 growing season, South Dakota State University soil tarping researchers collaborated with farmers across South Dakota to gain insight in farmer application of tarps. Farmer collaborators in South Dakota were each supplied with three tarp materials: black silage tarp, white silage tarp, and clear greenhouse plastic. Each farmer was told to use the tarp how they saw best fit for their operation. Farmers were given the opportunity to engage in field days and presentations to learn more about soil tarping. Each growing season, farmers worked with a team of researchers to collect data on soil temperature, moisture, and nitrogen. This data was collected through soil samples and HOBO moisture and temperature sensors that logged values hourly. Farmers also provided observations, photos, and dates for tarp removal and application along with comments on how well tarping fit into their system. While research studies can provide important details of tarping impacts on weed suppression and soil health, it is important to showcase the reality of how applicable this technique is for farmers in the real world.
Cover crops offer multifaceted benefits including soil health improvement, nutrient management, erosion control, and suppression of pests, diseases and weeds. This study examined the impact of fall cover crop (FCC) for enhanced soil properties and suppression of weeds and diseases, top priorities for chickpea growers. FCC was comprised of winter rye alone (in 2021) or in combination with hairy-vetch (in 2022-2023). To assess soil property changes, 5 quadrants (50 cm x 50 cm) representing each dense (≥ 96%), poor (10-35%) and no-growth (0%) FCC areas were sampled annually in April. Soil nutrients and biomass accumulation was measured and compared. For weed suppression, five treatments were compared: till- green manure (GM), GM plus pre-emergence herbicide (GMH), and no-till after termination via crimp-mulch (CM), kill-mulch (KM) or mow-mulch (MM). In 2023, significantly higher fresh (514 t/ha) and dry (140 t/ha) biomass was added to the soil from densely and sparsely FCC areas, respectively. Weed suppression was better on GMH than GM for the first 6-8 weeks but reached an average of ≥ 67.5% when monitored 92 days after chickpea planting. Similarly, no-till planted chickpeas after CC terminations in 2021 suppressed weeds during early stages but not in 2022. In both years, it was not possible to harvest chickpeas after no-till due to overwhelming weed infestation. Although added organic matter was evident across all years, FCC alone did not significantly suppress weeds in 2022 and 2023. Slightly different results are anticipated with adjustments in termination timing and conditions favoring mulch establishment in 2024 growing season.
Sweetpotatoes (Ipomoea batatas L.) are among the most important food crops worldwide, but production in Missouri is limited. Weed competition, especially early in the growing season, is a major factor impacting sweetpotato yields. The objective of this study was to optimize early season weed control in sweetpotatoes using fall seeded cover crops and spring applied herbicides. Cover crops, cereal rye (Secale cereale L.) or winter wheat (Triticum aestivum L.), were seeded in the fall. Before sweetpotato transplanting the following spring, glyphosate was applied to terminate cover crop growth along with flumioxazin as a residual herbicide. In designated treatments, S-metolachlor was applied 3 weeks later to extend residual activity. A total of eight treatments, including an untreated control, and a second control consisting of herbicides followed by tillage and hand-weeding as Missouri standard practice, were arranged in a randomized complete block design with four replications. Sweetpotato ‘Beauregard’ slips were transplanted in early June 2023. By 4 weeks after transplanting (WATr), weed biomass in cover crop plus herbicide plots was reduced by 99.3% and 86.3% for broadleaf and grass weeds, respectively, compared to the untreated control. An orthogonal test found that sweetpotato production in plots that received winter wheat as cover crop resulted in a significantly higher yield compared to plots that received cereal rye as a cover crop. Winter wheat combined with flumioxazin applied PRE and S-metolachlor applied as an overlapping residual herbicide demonstrated the greatest yield among all treatments, resulting in over 200-fold greater yield compared to the untreated control. The Missouri standard practice, represented as the weed-free control, produced statistically the same yield as the best treatment. However, this was the most time-consuming and labor-intensive practice and would be challenging for commercial production. Collectively, our results suggest that sweetpotato production in Missouri should consider integration of cover crops and herbicides to allow strong establishment of sweetpotato vines early in the early growing season, and hence ensure higher profitability without intensive labor inputs.
The United States ranks second in strawberry production worldwide. Much of this production has been transitioned from perennial matted row to annual plasticulture production. However, in states like Indiana, growers are exploring a hybrid system: multi-year plasticulture production. In response, we explored cover crops for row-middle weed management in plasticulture strawberry production. In September 2022, we planted ‘Chandler’ strawberry plugs into white polyethylene-mulched rows at Lafayette and Vincennes, IN. We established five row-middle treatments: nontreated and wheat straw mulch controls and three cover crops (oats, cereal rye, and white clover). The oats were winter-killed, and the cereal rye was roller-crimped in mid-May of 2023. Data collected included percent cover crop and weed canopy (per 0.09 m2); frost-killed flowers, live flowers, and developed fruits per plant within 2 weeks after the last spring frost; and total fruit number and yield per plant. At 7 weeks after transplanting (WAP), the oats canopy (82%) was greater than that of cereal rye (61%) and white clover (22%) but less than straw mulch (96%). Weed canopy in the straw mulch and oats was 6%, less than the nontreated control (38%). At 27 and 35 WAP, the cereal rye canopy was 96% and 100%, respectively; while the other treatments had less than 85% and 74% coverage, respectively. At 27 WAP, cereal rye and oats at both sites and straw mulch at Vincennes had less weed canopy (< 7%) than the nontreated control (>63%). At 35 WAP, only cereal rye had no weed canopy. At Lafayette, all treatments had 15 frost-killed flowers per plant. At Vincennes, all treatments had 8 frost-killed flowers per plant, except cereal rye (2 frost-killed flowers per plant). There were no differences among treatments in the live flower count. The number of developed fruits at both sites was significantly greater with cereal rye (8 fruits per plant) compared to all the other treatments (≤ 5 fruit per plant). Total harvested fruit number and yield at Lafayette was 17 fruits per plant and 135 g per plant for all treatments. At Vincennes, cereal rye resulted in significantly greater fruit number (10 fruits per plant) and yield (99 g per plant) compared to all other treatments (≤ 5 fruit and ≤ 49 g per plant). This study demonstrated that cereal rye was the most effective choice for suppressing weeds while maintaining or increasing strawberry yield in the first year of a multi-year plasticulture production system.
Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) are the two most troublesome pigweeds in crop production systems in the United States. These pigweeds just started to appear in the Pacific Northwest (PNW). A coordinated extension and outreach effort among land-grant universities (University of Idaho and Oregon State University), Amalgamated Sugar, other commodity commissions, and industry was launched to track Palmer amaranth and waterhemp in the PNW. In 2023, tissue samples were collected from pigweeds suspected to be Palmer amaranth and waterhemp and sent to Colorado State University for KASP genotyping test to confirm if the species were Palmer amaranth and waterhemp. The KASP test confirmed that the suspected pigweeds were Palmer amaranth and waterhemp. Since the majority of these pigweeds survived multiple applications of glyphosate, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication analysis was conducted to confirm possible glyphosate resistance in the Palmer amaranth and waterhemp populations. About 70% (17 out of 23) of the Palmer amaranth tissue samples showed gene duplication of up to 184 EPSPS gene copies, indicative of glyphosate resistance. All three populations of waterhemp showed gene duplication of 5.7 to 9.2 EPSPS gene copies indicative of glyphosate resistance. The widespread glyphosate resistance in the samples collected suggests that Palmer amaranth and waterhemp being introduced into the PNW are coming from States where these weeds have developed resistance to multiple herbicide groups. This would have huge implications for weed control in vegetables and other crops in the PNW.
In recent years, doveweed [Murdannia nudiflora (L.) Brenan] has become a pressing concern in Florida and nearby regions due to its rapid expansion and challenging eradication. Despite being considered a warm-season annual broadleaf, its grass-like foliage often enables it going unnoticed within the canopy, especially at early growth stages. Such camouflage allows for quick proliferation and rapid invasion leading to dense mats outcompeting desired turfgrass sward. Limited reliable herbicides exist, and their efficacy declines once the plants get established. Hence, there is a demand for options capable of controlling mature populations. This study assessed the efficacy of mesotrione at 0.37 L ha-1 or 0.58 L ha-1, simazine at 1.10 L ha-1 or 1.83 L ha-1, and their combinations for the late-season control of established doveweed in bermudagrass ‘CR-01’ maintained as a golf course fairway or athletic field at West Florida Research and Education Center in Jay, FL. When used independently, mesotrione alone provided inconsistent control, never surpassing 50%, whereas simazine alone yielded a maximum control of 80%) was achieved within 2 to 6 weeks after the initial treatment, contingent upon the rate, with higher rates yielding a more rapid response. Moreover, the control remained persistent until the conclusion of the study. Severe phytotoxicity was evident in all mesotrione-containing treatments, yet the turf recovered to acceptable levels within 4 weeks following each application.
Targeted spray application technologies have the capacity to drastically reduce herbicide inputs but to be successful, performance of both machine vision (MV) based weed detection and actuator efficiency need to be optimized. This study assessed 1) the performance of spotted spurge recognition in ‘Latitude 36’ bermudagrass turf canopy using the You Only Look Once (YOLOv3) real-time multi-object detection algorithm, and 2) the impact of various nozzle densities on model efficiency and projected herbicide reduction under simulated conditions. The YOLOv3 model was trained and validated with a dataset of 1,191 images. The simulation design consisted of 4 grid matrix regimes (3 × 3, 6 × 6, 12 × 12, and 24 × 24) which would then correspond to 3, 6, 12, and 24 non-overlapping nozzles, respectively; covering a 50-cm wide band. Simulated efficiency testing was conducted using 50 images containing predictions (labels) generated with the trained YOLO model and, by applying each of the grid matrixes to individual images. The model resulted in prediction accuracy of a F1 Score of 0.62 precision of 0.65 and recall value of 0.60. Increased nozzle density (from 3 to 12) improved actuator precision and predicted herbicide-use efficiency with a reduction in false hits ratio from ~30% to 5%. The area required to ensure herbicide deposition to all spotted spurge detected within images was reduced to 18% resulting in ~80% herbicide savings compared to broadcast application. Slightly greater precision was predicted with 24 nozzles, but not statistically different from the 12-nozzle scenario. Using this turf/weed model as a basis, optimal actuator efficacy and herbicide savings would occur by increasing nozzle density from one to 12 nozzles with the context of a single band.
The economic significance of hemp (Cannabis sativa L.) as a source of grain, fiber, and flower is rising steadily. However, due to the lack of registered herbicides, hemp growers have limited weed management options. Slow-growing hemp varieties can be outcompeted by weeds for sunlight, water, and nutrients. Hence, easily adoptable integrated weed management (IWM) strategies are essential. Addressing these challenges necessitates novel approaches to identify quantitative phenotypes and explain the genetic basis of key weed-competitive traits. Plant height and canopy architecture may affect crop-weed competition. However, manually measuring these parameters is a time-consuming process. The PlantEye (PE) multispectral 3D scanner was selected as the high-throughput digital phenotyping technology for the evaluation of plant architecture. In this study, the suitability of digital phenotyping was evaluated at the Clemson University Coastal Research and Education Center to screen diverse hemp varieties with different plant habits. Digital plant biomass, plant height, and plant 3D-leaf area (including leaf area index, leaf angle, and light penetration) were periodically monitored. We performed a range of validation tests for morphological features (digital biomass and plant height). A significant correlation (P < 0.001) was observed between digital biomass and manually measured biomass (R = 0.89), as well as between digital height and manually measured height (R = 0.94), indicating the high precision and usefulness of 3D multispectral scanning in measuring morphological traits. Multispectral analyses used in this study are non-destructive, rapid techniques with minimal error and human interference, which have great potential for use in planning weed management.
Managing weeds is one of the most significant challenges, especially in organic vegetable production systems. Farmers control weeds in various ways, many of which can have negative environmental impacts. Cultivation is a common way many organic vegetable growers will manage weeds; however, it leads to decreased soil health properties. Hand weeding is extremely time-consuming and labor-intensive. Conventional herbicides have raised public concern for their impact on human health and the environment. Organic herbicide products are used as a burndown, post-emergence product but can be cost-prohibitive. In addition, there is a lack of current research comparing organic herbicide effectiveness on a range of common weed species. This study aimed to explore the efficacy of five Organic Materials Review Institute-approved organic herbicides. These products included citrus oil (Avenger®), ammonium nonanoate (AXXE®), acetic acid (Green Gobbler®), caprylic acid capric acid (HomePlate®), and clove oil cinnamon oil (Weed Zap®). Water was used as a control, and glyphosate (Ranger Pro®) was used as a positive control. Each herbicide was tested on six common weed species: Chenopodium album (common lambsquarters), Portulaca oleracea (common purslane), Setaria viridis (L.) Beauv. (green foxtail), Digitaria sanguinalis (L.) Scop. (large crabgrass), Amaranthus retroflexus (redroot pigweed), and Abutilon theophrasti (velvetleaf). Products were sprayed according to label recommendations using a calibrated spray chamber at the Iowa State University greenhouses. Each weed species, 10 plants per replication, was sprayed after reaching an average height of seven centimeters. Percent weed cover using digital image analysis software (Turf Analyzer) and percent visual injury was recorded. These data parameters were collected 24 hours, 3 days, 10 days, 17 days, and 21 days following herbicide application. Weed biomass was collected and dried 21 days after herbicide application for all species. AXXE® was a fast-acting herbicide on common lambsquarters, common purslane, redroot pigweed, and velvetleaf. These species showed over 85% injury three days after AXXE® application. Weed Zap® stunted the majority of examined weed species soon after application, but the injury effects were less significant 21 days after application. Visual injury assessments showed Avenger®, Green Gobbler®, HomePlate®, and Weed Zap® had no significant injury on green foxtail and large crabgrass 21 days after herbicide application. Results from this study provide growers with practical and applied data to make informed decisions regarding the use of organic herbicides.
Industrial hemp is receiving attention for its numerous benefits, particularly in the fiber industry. Weed competition is a primary concern for hemp cultivation causing reduced yields and inferior-quality fiber. However, little is known about herbicide application in hemp since a limited range of herbicides are available for hemp production. Therefore, a field study was conducted in 2023 to investigate the effect of different herbicides and application timings on weed suppression, crop injury, growth, and biomass yield of hemp. A randomized complete block design was conducted with six herbicide treatments including, early POST [2 weeks after planting (WAP)] and late POST (5 WAP) emergence applications of S-metolachlor, clopyralid, and ethalfluralin, with an untreated control to make comparisons. Plant stand showed no significant difference among treatments. Early POST herbicides application significantly reduced the weed biomass compared to untreated control at 7 WAP. By 10 WAP, weed biomass became comparable across treatments. At harvest, untreated control recorded comparatively higher weed biomass than early POST treatments and late POST ethalfluralin. Plant height remained non-significant among treatments until 10 WAP. At harvest, control showed no variation with late POST treatments but recorded an average 63% lower plant height than early POST applications. Treatments showed no significance for hemp biomass at 10 WAP. However, early POST S-metolachlor and ethalfluralin herbicides exhibited lower weed biomass and greater plant height, resulting in greater hemp biomass accumulation compared to untreated control at harvest. In conclusion, early POST S-metolachlor and ethalfluralin could be used as POSTemergence herbicides for hemp cultivation.
Planting-hole Steam Application for Pathogen and Weed Control in Organic Strawberry in Southern California - Oleg Daugovish Elucidating the Impact of Anaerobic Soil Disinfestation on Organic Watermelon Production in South Carolina - Sohaib Chattha Alternative Carbon Sources for Anaerobic Soil Disinfestation in California Strawberry - Oleg Daugovish Sweetpotato (Ipomoea batatas) Variety Tolerance to Different Herbicidal Weed Control Methods - Alyssa Miller Soil Steaming: A Sustainable Weed Management Strategy in Sweetpotato - Alaina Richardson Assessment of Various Carbon Sources for Anaerobic Soil Disinfestation to Manage Weeds in Organic Sweetpotato - Simardeep Singh Evaluation of saturated steam with boiling water to control Guinea grass (Megathyrus maximus) in riparian
Organic strawberry production has been expanding in California, but opportunities for crop rotation are limited due to lack of organically certified fields. Continuous strawberry production promotes soil-borne pathogens, such as Macrophomina phaseolina, the causal agent of charcoal rot and increases populations of weeds. These problems are exacerbated by lack of cost-effective management tools. In summer and fall production seasons at Oxnard, CA we evaluated pre-plant steam injection to raise soil temperature to 70 C or above for at least two minutes. Steam generated on-site was applied via four 25-cm long spikes to planting holes in raised beds covered with the plastic mulch. Five to ten days later, bare-root strawberry plants were placed in six steamed and six untreated plots and their performance and fruit production assessed. Additionally, we collected soil at 0-25 cm for analyses of resident Macrophomina phaseolina abundance before and after treatment and evaluated weed densities in planting holes. Steam application reduced M. phaseolina microsclerotia levels 80% in summer and 96% in fall. Steaming provided near 100% control of weeds germinated from the soil seed bank, but had no effect on germination of wind-dispersed weeds deposited to holes after steaming as was the case with fumigants. In summer season, strawberry mortality due to soil-borne pathogens was 12-18% in steamed plots and 70-75% in untreated soil. Due to loss of plants, marketable fruit yields in untreated plots were reduced 95% compared to steam treatment. No early-season plant mortality occurred in fall season but strawberry plants were 39 and 54% larger at two evaluation dates in steamed plots compared to untreated soil. We continue evaluations of fruit production and plant responses to soil pathogens. The completed work suggests that hole steaming may be very effective in suppressing soil-borne pathogens and weeds interfering with organic strawberry production in coastal California.
Weeds and soil-borne pathogens are limiting factors in organic watermelon (Citrullus lanatus) production. Yellow nutsedge (Cyperus esculentus) is a problematic weed for Southeastern watermelon growers. Fusarium wilt caused by Fusarium oxysporum f.sp. niveum (FON), is responsible for significant yield loss in watermelon production. Inefficient non-chemical tactics are an impediment to curtail weeds and soil-borne diseases in organic watermelon; and necessitate the adaption of an alternative strategic and holistic approach. Anaerobic soil disinfestation (ASD) has the potential to control weeds and soil-borne pathogens across a range of environments and crop production systems. ASD is a preplant chemical independent technique, which requires incorporation of labile organic carbon (C) sources into the soil, followed by tarping the soil with plastic mulch, and irrigating the soil to the saturation. Shifts in soil microbial communities and production of volatile organic compounds during ASD process are the main mechanisms that are believed to kill soil-borne pathogens and weeds seeds. The objectives of this study were to 1) determine whether ASD can suppress the emergence of yellow nutsedge, 2) compare the efficacy of locally available C sources, 3) evaluate if ASD can influence grafted and non-grafted watermelon yield. A field trial was conducted at Clemson University’s, Coastal Research and Education Center in Charleston, South Carolina in 2023. The study was arranged in a randomized complete block design with four replications. Main C sources were subjected to control (CT) with no C, chicken manure molasses (CMM), and cotton seed meal (CSM). All treatments were assigned as ASD with non-grafted (Powerhouse) and grafted (Carolina strongback) rootstock grafted to scion Powerhouse. Indicators of reduction in soils (IRIS) tubes paint removal (%), yellow nutsedge shoot count, and crop yield data were recorded. Higher anaerobic soil conditions and lower yellow nutsedge shoot count were observed in ASD plots. At the time of watermelon harvest, total number of yellow nutsedge shoot count were recorded as 65, 25, and 22 in CT, CSM, and CMM, respectively. Higher marketable fruit yield was recorded in ASD plots treated with CMM. Based on weed control and yield assessments, CMM to facilitate ASD is an ideal practice for growing organic watermelon in South Carolina.
Anaerobic soil disinfestation (ASD) has been adopted in approximately1,000 ha in California strawberry production as an alternative to chemical fumigation of soil. Rice bran, the predominant carbon source for ASD, has become increasingly expensive. In 2022-2024 field studies at Santa Paula and Oxnard, CA we evaluated 20-30% lower-priced wheat middlings (Midds) at 6 or 7 t/acre as alternative carbon sources to rice bran. The ASD treatments were applied in August at each location in preparation for strawberry planting in October. Soil and air temperatures were 18-35 C during that time. After incorporation of carbon sources into the top 30 cm of bed soil, beds were shaped, irrigation drip lines installed and covered with totally impermeable film (TIF) to prevent gas exchange. Beds were irrigated to full capacity within 24 to 72 hours after TIF installation. Anaerobic conditions were measured with oxidation reduction potential (ORP) sensors placed at 15 cm depth. Midds plots maintained Eh at -180 to 0 mV during the two ASD weeks at Santa Paula and -300 to 0 mV during five weeks at Oxnard, while untreated soil was aerobic at 200 to 400 mV. At Santa Paula, permeable bags with inoculum of Macrophomina phaseolina, a key soil borne pathogen of strawberry, and tubers of Cyperus esculentus, the most difficult to control weed, were placed 15 cm deep in soil and retrieved two weeks after ASD initiation for analyses. At Oxnard, resident populations of M. phaseolina and C. esculentus in soil were assessed before and after ASD. Two weeks after the completion of ASD, holes were cut to aerate beds and bare-root strawberry were transplanted into them: ‘Fronteras’ at Santa Paula and ‘Gaviota’ at Oxnard. ASD with Midds reduced viable microsclerotia of M. phaseolina 75% at Santa Paula and 98% at Oxnard. ASD treatments reduced tuber germination of C. esculentus 68-74% compared to untreated soil. Additionally, Midds and DDG provided greater sufficiency of plant-available nitrogen and increased fruit yields 40%, compared to untreated soil at Santa Paula. We continue fruit production evaluations at Oxnard in 2024. ASD with wheat middlings as a carbon source can suppress soil pathogens and weeds and help sustain organic strawberry production in California.
There are limited herbicides labeled for use in sweetpotato (Ipomoea batatas) production in the United States. Therefore, the registration of additional herbicides with different modes of action (MOA) would provide growers added weed control options to enhanced crop yield and provide a more sustainable sweetpotato (SP) production system. As herbicide-resistant weed populations continue to emerge and become more prevalent, weed control strategies need to include herbicides with different MOAs for the long-term success of (SP) cultivation. This research will identify herbicides, along with rate and application time that could be registered for use in sweetpotato. Herbicide tolerance of four (SP) varieties (Beauregard, Orleans, Dianne, and Covington) were evaluated in a screening study. These varieties were selected to represent sweetpotato production areas across the United States in Arkansas, California, Louisiana, Mississippi, and North Carolina. Herbicides evaluated include fluridone, glyphosate, glufosinate, carfentrazone, saflufenacil, acifluorfen, and others. The study involved the foliar application of herbicide treatments at 1X and 0.5X rates, laid out in a completely randomized design, using a spray chamber onto individual (SP) plants cultivated in 4x4 inch containers within the controlled environment of the Dorman Hall Greenhouse at Mississippi State University. Visual assessments of herbicide-induced injury were conducted at regular intervals of 7, 14, 21, and 28 days after treatment (DAT), accompanied by measurements of vine length in centimeters. Furthermore, dry root and shoot biomass were quantified at 28 DAT to provide a comprehensive assessment of herbicide impacts on (SP) growth and development. Data was analyzed using ANOVA and means separated by Fisher’s protected LSD (α=0.05). Results indicate varying levels of tolerance among the (SP) varieties to specific herbicides and application rates. Noteworthy trends in visual injury, vine length, and biomass measurements highlight the nuanced responses of the cultivars to different herbicide chemistries.
The Sweetpotato (Ipomoea batatas (L.) Lam.) has flexible uses as food, feed, and industrial product usage. There are over 27,000 acres across one-hundred and fifty farms in Mississippi and the state also ranks second and third in the nation in acreage and production, respectively. It is paramount for all farmers to suppress weed species, enhance biodiversity, improve soil health, and minimize pests and diseases in plants. In sweet potatoes, there is a significant problem with weeds interfering with yields, reducing crop yield by up to 80%. A chemical approach is usually the most popular utilization, but it can lead to disadvantages with crop quality, intolerance, and, in worst-case scenarios, environmental toxicity. To overcome limited weed control options and preserve or improve sweet potato quality and yield for Mississippi growers, there is a great need to find a supplemental weed control strategy. One solution is the utilization of soil steaming, an alternative method that is environmentally friendly and organically favored. This study aimed to assess the most effective soil steaming depth and duration for controlling a troublesome weed in sweetpotatoes, yellow nutsedge (Cyperus esculentus (L.)). This study is conducted in split plot designs with the soil steaming plots as the main plots in field and greenhouse situations. This was to test different durations of times and depths in the soil for both areas. Depths of 2, 5, and 8 inches, were used. Times of 0, 1, 5, 20, 45 minutes, were used. Maximum temperatures reached were 82 ºC. The germination count was recorded at 21 DAT. The highest weed coverage (55%) was observed in 0 minutes duration. The second highest (30%) was observed at 5 minutes. The least amount of coverage (20%) was observed at 20 minutes. The adoption of soil steaming would be beneficial in sustainable suppression of yellow nutsedge in organic sweetpotato farms. Keywords: soil steaming, weed suppression, sweetpotato, sustainability, organic
Yellow nutsedge (Cyperus esculentus L.) management in organic plasticulture systems is challenging as it reproduces both by seeds and tubers. Yellow nutsedge has a strong midrib and sharp leaf tip which allows it to puncture plastic mulch and creates favorable conditions for other weeds to grow, compete for resources with crop plants, and decrease crop yield. Lack of available herbicide options in specialty crops make weed management more challenging. Anaerobic soil disinfestation (ASD) is a technique that has shown potential to manage weeds in organic production systems. ASD is facilitated by incorporating carbon sources into the soil, tarping the soil with plastic mulch, and irrigating to the soil saturation. A field study was conducted at Clemson University’s Coastal Research and Education Center, Charleston, South Carolina, to evaluate the impact of various carbon sources in ASD on weed management in organic sweetpotato. This treatment structure for this study consisted of a factorial with four carbon source treatments (cotton seed meal, chicken manure molasses, brassica waste, and non-amended control) and four sweetpotato cultivars (Bayyou Belle, Muraski, Monaco, and USDA 18-040). These sweetpotato cultivars have two different growth habits, either bunch type (USDA 18-040 and Monaco) or spreading type (Bayyou Belle and Muraski). The primary purpose of using different plant architecture is to evaluate the impact of the sweetpotato vine growth habit on weed emergence. Experimental plots receiving chicken manure molasses and cotton seed meal as carbon source resulted in the greatest cumulative anaerobic conditions (
Boiling water and steam have been effectively used as a non-chemical means to control weeds in croplands and urban areas. In Hawaii, it is a relatively new technology with limited trials done on local conditions and weeds. Guinea grass (Megathyrsus maximus) is a noxious weed that invades landscapes and agricultural fields in Hawaii and throughout the world. While it is typically controlled using herbicide sprays, this may be restricted if the guinea grass being controlled is located in riparian areas. In this study, we evaluated the efficacy of saturated steam with boiling water in controlling mature clumps of guinea grass growing along a streambank. Guinea grass bunches were divided into small (less than 15.2 cm) and large clumps (15.2 to 30.5 cm) and then cut 5 to 15 cm from the ground. Cut clumps were either not treated (control) or treated with saturated steam and boiling water for 1 minute using a 15cm long spike injector inserted into different points of the crown. Percent green color and number of resprouts were collected 7, 14, and 21 days after application. Dry biomass was collected 22 days after application. Results indicate that saturated steam with boiling water was effective in controlling guinea grass clumps. Small clumps were completely controlled (no resprouts and new biomass) while large clumps had significantly reduced the number of resprouts and reduced production of new biomass. Saturated steam with boiling water offers a non-chemical means to control guinea grass in riparian areas in Hawaii.
A Water Soluble β-triketone Enriched Extract of Manuka Oil has Increased Efficacy Compared to Vinegar and D-Limonene in a Field and Greenhouse Evaluation - Casey Barickman Weed Control in Bell Pepper after Herbicide Application in a Reduced Sunnhemp Cover Crop Population. - Peter Dittmar Assessing the Effects of Container Sizes and Weed Densities on Weed-ornament Competition in Nursery Container Production - Debalina Saha Herbicide-Resistant Italian Ryegrass in Oregon Hazelnut Orchards: Evaluating Nonchemical and Chemical Methods - Marcelo Moretti Limiting Liverwort Growth by Allelopathic Effects of Organic Mulches in Ornamental Production - Manjot Sidhu Effect of Application History on Preemergence Herbicide Persistence - Travis Gannon
Weed management strategies for specialty and organic crop production are challenging due to limited chemical weed control products with good efficacy that are cost effective. The need for new bioherbicide modes of action has become increasingly urgent in modern agriculture as most bioherbicides have nonspecific modes of action with no systemic activity. Introducing new modes of action is essential to diversify weed control strategies, minimize the risk of resistance development, and ensure sustainable weed management practices. By fostering innovation in bioherbicide development and promoting the use of novel modes of action, we can safeguard our agricultural systems, reduce the environmental impact of weed management, and maintain the ability to feed a growing global population while preserving the long-term health of our ecosystems. Manuka oil is derived from the leaves and branches of the Manuka tree (Leptospermum scoparium) and contains β-triketones. The β-triketone rich fraction contains leptospermone and inhibits a key enzyme, p-hydroxyphenylpyruvate dioxygenase (HPPD). This process directly inhibits carotenoid biosynthesis, upstream in the biochemical pathway, which causes damage to the photosynthetic apparatus and leads to bleaching of the leaf tissue which eventually kills the plant. The β-triketone extract at 2% and 4% had up to 97% control against different weed species in field and greenhouse evaluations. The β-triketone extract was significantly more efficacious verse other bioherbicides such as the 20% vinegar and 12.5% D-limonene. Additionally, the β-triketone extract was just as effective as the 2% glyphosate treatment in the greenhouse evaluation against Amaranthus palmeri and Digitaria sanguinalis. The β-triketone extract also reduced Cyperus esculentus growth by 70% at 9 days after treatment. Thus, there is significant evidence that commercializing a water soluble β-triketones enriched extract of Manuka oil can be an effective weed control strategy in crop production systems, especially in specialty and organic cropping systems where the need of bioherbicides is critically imperative.
Sunnhemp cover crop seed germination can be lowered due to poor seed quality, incorrect planting depth, or adverse weather effects. The objective of this research is to evaluate weed control by herbicides in a reduced sunnhemp population. Research trials were conducted at the Plant Science Research and Education Unit, Citra, Florida, and the Syngenta Vero Beach Research Center, Vero Beach, FL. The treatments were sunnhemp at 44.83 kg/ha, sunnhemp at 22.4 kg/ha ( no herbicide, bentazon at 1.12 kg/ha, sulfentrazone at 0.14 kg/ha, halosulfuron at 0.04 kg/ha, glyphosate at 5.5 kg/ha followed by glyphosate at 5.5 kg/ha, and oxyfluorfen at 0.56 kg/ha), and a nontreated weed fallow. Sunnhemp was planted in Citra on July 18, 2023 and in Vero Beach on July 27, 2023; herbicides were applied 2 weeks after planting when the sunnhemp were 15 to 25 cm tall. After 8 weeks of growth, the sunnhemp was mowed and the field was prepared for laying plastic and planting bell pepper. The oxyfluorfen caused significant injury to the sunnhemp; this treatment had similar broadleaf, grass, and nutsedge populations to the weed fallow. In Citra at 14 and 28 days after application, bentazon, sulfentrazone, or halosuluron had lower populations than sunnhemp at 22.4 kg/ha alone, but at cover crop termination all the cover crop treatments had similar nutsedge control. All cover crop alone and cover crop herbicide treatments had similar grass and broadleaf control at crop termination. In the bell pepper crop at Vero Beach, oxyfluorfen had greater nutsedge populations than all the other treatments. Crop yields were similar among the cover crop alone or with a herbicide. The application of a herbicide in a reduced cover crop population is not necessary for increased weed control in a fall cash crop. However, the reduced cover crop population in this study was artificially created so the sunnhemp population was equal spaced through the entire plot. If the sunnhemp is significantly impacted like the oxyfluorfen treatment, then more intense recovery action may be necessary.
Effective weed management strategies are essential for producing high-quality and successful ornamentals in nurseries and greenhouses. Weeds can affect both the productivity and quality of ornamentals, especially in containers where nutrient and moisture availability are limited, due to restricted space. The objective of this study was to determine how different types of weed species at various densities and in different container sizes affect the growth of ornamental plants. Two rounds of greenhouse experiments were conducted at the Horticulture Teaching and Research Center, Michigan State University, in summer and fall 2023. Seeds of large crabgrass {Digitaria sanguinalis (L.) Scop} and smooth pigweed (Amaranthus hybridus L.) were grown separately until they attained the 4-6 leaf stage. Liners of hydrangea {Hydrangea macrophylla (Thunb.) Ser.} and syringa (Syringa vulgaris L.) were planted in containers of three different sizes 0.67 gallons (2.54 liters), 1.5 gallons (5.67 liters), and 3 gallons (11.35 liters) containing standard bark-based substrate amended with controlled-release fertilizer. All plants received 0.5 inches (1.3 cm) of water thrice daily and were allowed to grow till they were well established. Then the weed seedlings of large crabgrass and smooth pigweed were carefully transplanted to each container-grown ornamental plant at different densities of 0,1,3,6 per pot, with the density of 0 being the control set. After weed transplantation, all pots were maintained inside the greenhouse for 8 weeks. The experimental design utilized a randomized complete block design with six replications per treatment. Initial and final growth indices of ornamentals were recorded. At 8 Weeks After Potting (WAP) fresh weights of both the weed species and the ornamentals were recorded separately. All data were analyzed in SAS by ANOVA and the Tukey’s HSD test were performed to separate out the means. Results showed that final growth indices of hydrangea were significantly higher than syringa and maximum in 3-gallon containers. Overall, large crabgrass at density of 6 was more competitive than smooth pigweed and hydrangea performed better than syringa in 3-gallon container size in competing the weed species.
Herbicide-resistant Italian ryegrass (Lolium multiflorum Lam.) presents a significant challenge in hazelnut orchards across Oregon, with confirmed resistance to multiple herbicide modes of action groups (1, 2, 9, 10, 15, and 22). Four field studies were conducted in 2023 to evaluate nonchemical and chemical methods for controlling Italian ryegrass during spring. Tested treatments included mowing at 2 km h-1, electric weeding control (EWC) at 15 MJ ha-1 (2 km h-1), and glufosinate application at 1.68 kg ai ha-1, administered once or twice. Furthermore, combinations of EWC with mowing or glufosinate were examined, resulting in eleven treatments. EWC was performed using alternating current and 30 kW (EH-30 Thor, ZassoTM), treating swaths 1.2 m wide. Assessments conducted 56 days after initial treatment (DAIT) revealed that single mowing showed no significant difference compared to untreated plots. However, when mowing was performed twice, it led to a 30% reduction in inflorescence density and an 84% reduction in weight. EWC, applied once or twice, resulted in significant decreases in Italian ryegrass inflorescence density (51-58%), weight (55-73%), and shoot weight (45-75%) compared to untreated plots, with no significant differences observed between single or double applications. Similarly, glufosinate applied once or twice substantially reduced Italian ryegrass inflorescence density (68 to 86%) and weight (73 to 93%). Combinations of EWC with mowing or glufosinate demonstrated high efficacy, achieving control rates of 89 to 96% and exhibiting comparable efficacy to two applications of glufosinate (96%). These findings suggest that EWC, when applied during the spring period, can effectively control Italian ryegrass, offering comparable efficacy to glufosinate and superior efficacy to mowing.
Liverwort (Marchantia polymorpha) is one of the problematic weeds in ornamental crop production that deteriorates the quality and aesthetic value of ornamentals. To study the effectiveness of allelopathic properties of organic mulch extracts, six different organic mulch materials including rice hull (RH), cocoa hull (CH), pine bark (PB), maple leaf (ML), shredded cypress (SC) and red hardwood (HW) were used for obtaining mulch extracts. The extracts were prepared by following the modified EPA 1312 synthetic precipitation procedure. In the lab experiment, the mulch extracts obtained were used to impregnate agar media at an increasing dose at either 1x (2ml), 2x (4ml), 3x (6ml), and 4x (8ml) rates. Ten gemmae were transferred to the culture medium in each petri dish and all petri dishes containing gemmae were maintained inside the growth chamber. Data was recorded for number of gemmae germinating in each petri dish and at the end of experiment, the length and width of the thallus derived from each gemmae were measured. For greenhouse experiment, the mulch extracts were applied to nursery containers filled with standard substrate and amended with controlled-release fertilizer for assessing the postemergent liverwort control in nursery containers. Either RH, HW, CH, ML, SC or PB mulch extracts were applied to each of the container uniformly at either 1X (15ml), 2X (30ml), 3X (45ml), and 4X (60ml) rates, at the beginning of experiment and bi-weekly until 10 weeks. Control set without any mulch extract was included as well. Percent of substrate surface covered by liverwort thalli was visually estimated bi-weekly until 10 weeks after first treatment. Fresh biomass of the thalli and number of gemmae cups in each pot were also recorded at the end of the experiment. Both lab and greenhouse experiments had four replications per treatment and were arranged in a randomized complete block design. After 1 week in the growth chamber, ML followed by SC, PB and RH extracts showed maximum suppression of liverwort gemmae germination. At 2 weeks, all rates of ML provided complete inhibition of liverwort. In the greenhouse, all the mulch extracts were able to provide complete liverwort control for the first two weeks. PB and HW mulches showed excellent liverwort control and minimum biomass of liverwort after 10 weeks as compared to other mulches. Hence, the allelopathic potential of the organic mulches can be a promising option for biopesticidal control of liverwort, and a component of integrated liverwort management.
Preemergent herbicides are commonly applied to control many annual weed species in turfgrass systems. Oxadiazon and prodiamine are pre-emergent herbicides that effectively inhibit the growth of emerging annual grasses and broadleaf weeds without harming certain turfgrass species. However, in recent years, a decline in the efficacy of oxadiazon and prodiamine has been observed by golf course managers, leading to an increase in application rates in an attempt to mitigate the issue. Therefore, the objective of this study was to characterize degradation processes that affect oxadiazon and prodiamine persistence and efficacy in order to identify solutions or mitigation strategies. Soil samples were collected from unique sites throughout North Carolina. Field studies were organized as a randomized complete block design containing 3 replications and 2 experimental runs. Treatments were arranged in a split-split plot design, where the whole plots consisted of 4 sites with histories of continuous oxadiazon or prodiamine use (never applied, applied 1-2 years, ~7 years, > 15 years), the sub-plots were 2 treatments (non-sterilized and sterilized), and the sub-sub-plots were 6 collection timings (14, 28, 42, 56, 112, and 168 days after treatment). Herbicide residue quantifications were determined using high-performance liquid chromatography. Data were recorded and converted into a percentage of the applied rate. A higher percent of oxadiazon was observed for sterilized soil (79.2%) compared to non-sterilized soil (73.7%). In the non-sterilized soil, at 14 DAT there were no differences between periods of use. However, at 28 DAT, the soil with no use history presented a higher percentage of oxadiazon (83.0%) compared to 1 and 15 years (75.5%, and 77.1% respectively). Furthermore, at 42 and 56 DAT, the soil with no history of application exhibited the highest percentage of oxadiazon among all periods of use. Findings of this study suggest that there is higher concentration of oxadiazon, meaning less degradation, in the soils with no history of application.
Evaluating Bacterial Diversity and Pest Control Efficacy of Steam Disinfestation Treatments in the Salinas Valley Spinach and Lettuce Fields - Erika Escalona Development of Minirhizotron for Nondestructive Rapid Detection of Parasitic Nematodes - Tim Pannkuk Genome Sequencing of Crapemyrtle Bark Scale for Developing Advanced IPM Strategies - Bin Wu A New Technique for Visual and Quantitative Assessment of Pesticide Applications to Tree Trunks for Control of Trunk-boring Insects - Amy Fulcher Factors Affecting Spray Coverage on Red Maple Trunks from an Air-Assisted Sprayer - Amy Fulcher Rice Hull Use in Container Production; Economics and Efficacy - Shawn Steed Organic and Synthetic Herbicides for Controlling Liverwort Growth in Containerized Ornamental Production - Manjot Sidhu Impact of Changing Climate on Weed Control in Ornamental Crop Production: A Potential Research Area - Supti Saha Mou Development of “EZA”, a New Pesticide Suitable for Organic Production of Horticultural Crops - Merci Uwimbabazi Impact of Partial Saltwater Agroecosystems on Weed Competition in Watermelon. - Joseph Bazzle
As the specter of climate change looms larger, sustainable and environmentally friendly alternatives for pest and pathogen control in agriculture are becoming increasingly imperative. Steam disinfestation, once an antiquated method overshadowed by chemical pesticides, is experiencing a resurgence due to heightened environmental concerns. Despite its historical use, there has been limited exploration of scaling up steam disinfestation for field applications in vegetable crops. Therefore, there is a central focus in this project to evaluate the efficacy of band steaming for disinfestation in spinach and lettuce fields in the Salinas Valley. This study seeks to advance the validation of banded steaming as a practical alternative to chemical fumigation by conducting a comprehensive assessment of vegetable productivity in lettuce grown in steamed soils versus non-steamed soils. The experiment utilized a custom-built steam applicator equipped with a low-pressure 1,000 kg/hour steam generator in Salinas, CA, during 2023. All research and trials were conducted at the Salinas Extension and USDA Center. In addition to evaluating efficacy of steam disinfestation for pest control, a preliminary evaluation of its impact on the soil microbiome was conducted on spinach and lettuce fields. Soil samples were collected before and after steam application, and crops were meticulously monitored for soil-borne disease and weed control, alongside yields at harvest. Preliminary results indicate effective weed control and lower pathogen pressure after steam treatments. Furthermore, the trials conducted from July 2023 to September 2023, involved verifying the performance of the steam applicator treatments, and assessing beneficial soil organisms using 16S sequencing in the spinach and lettuce fields. Through a thorough analysis of the outcomes derived from these trials, our objective is to offer in-depth insights into the overall efficacy of steam disinfestation and its potential implications for agricultural practices. This investigation is particularly focused on assessing its impact on the soil microbiome, the presence of pathogens, and its effectiveness in weed control.
Plant-parasitic nematodes are a historic problem in a wide range of horticultural and agronomic production conditions. Many horticultural crops can be negatively impacted during production since near-ideal environmental conditions are created for nematode growth and reproduction. Once established in the soil of a nursery, orchard, or greenhouse, there is also potential to spread the plant damaging nematodes via machinery, handheld equipment, soil movement, or footwear. Nematode presence may be detected by root visual symptoms of infected plants, but laboratory nematode assays are a more reliable diagnostic tool – however costly and time consuming. Our team developed a portable handheld infrared thermography-minirhizotron device for rapid, nondestructive detection of the presence or absence of plant parasitic nematodes. This self-contained device, using infrared thermography, processes images using an algorithm. It can be operated by trained personnel to perform on-site rapid diagnosis in a nursery environment. A prototype has been constructed and tested in laboratory setting. It is equipped with wireless communication and network capabilities, allowing remote access and control. The goal is to develop a smart device that can be scaled up and networked for early detection and rapid response to a wide range of soil nematodes of horticultural importance. The algorithm is developed to distinguish between root-knot and cyst nematodes in infected plants.
Crapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae), an invasive insect pest threatening horticultural industries, has spurred the search for sustainable control methods. Our recent research focused on two key aspects of CMBS behavior: feeding and mating. In feeding, our studies revealed that while nicotine does not affect the phloem salivation process in CMBS, it significantly impairs the insect’s ability to ingest phloem sap, suggesting that nicotine interferes with the precise muscular coordination in the acephalothoracia region of CMBS, thereby offering a potential mechanism for chemical control. By identifying the genes that encode nicotinic receptors, we can pinpoint potential chemical targets to disrupt CMBS feeding behavior. In studying mating behavior, we found that mating is crucial for CMBS reproduction. Solid-phase micro-extraction and GC/MS assays revealed that CMBS release unique volatile compounds at different life stages. By identifying the genes responsible for sex pheromone production and pheromone receptors, our research lays the groundwork for developing pheromone-based traps and mating disruption strategies. Moreover, the discovery of juvenile hormone receptors and their expression at various developmental stages suggests additional opportunities to hinder CMBS growth and reproduction. We are conducting a comprehensive genomic analysis of CMBS using PacBio SMRT, Hi-C, and Illumina genome sequencing. This genomic framework will be used to develop innovative pest control strategies to control CMBS populations while supporting integrated pest management (IPM) techniques and reducing environmental impact.
My integrated research and Extension programs focus on the evaluation, selection, and breeding of horticutlural specialty crops, as well as the study of insect-plant interactions and natural enemies. The goal is to develop integrated pest management (IPM) strategies for controlling... Read More →
Water sensitive paper (WSP), a yellow paper that stains blue in the presence of water, can be used to evaluate spray characteristics. While traditionally used as 2x3-inch cards placed in the canopy, we developed a WSP wrap that can be wrapped around a trunk, sprayed, and removed without damaging the trunk to assess spray distribution for control of trunk-boring insects. Trunk wraps are made by adhering a 1x8.5-inch strip of WSP to a 1.75x8.5-inch strip from a printable vinyl sticker sheet. To install, the adhesive is exposed, the wrap is manually wrapped around the trunk, and pressure is applied by gripping the wrapped portion of the trunk. However, the tapered shape, bumpy surface, and small trunk caliper, as well as humidity can cause wraps to unravel during experiments. In preliminary tests, 50% of uncoiled, i.e., flat, 4.25-inch wraps unraveled from 16.5 mm caliper Acer rubrum ‘Franksred’ Red Sunset® red maple trunks. Our objective was to test if pre-coiling wraps prevented unraveling. We tested four treatments with five replications each: 1. 8.5-inch wraps coiled and stored in 2-inch diameter PVC, 2. 8.5-inch uncoiled wraps, 3. 4.25-inch wraps coiled and stored in 0.75-inch PVC, and 4. 4.25-inch wraps coiled in 0.75-inch PVC and stored in 1-inch PVC. After 2 weeks of storage, we installed wraps on 16.5 mm caliper Red Sunset® trunks. After 5-10 minutes, we reapplied pressure to both 8.5-inch wraps and 4.25-inch flat wraps because they unraveled, our standard practice; both 4.25-inch pre-coiled wrap treatments remained tightly wrapped and did not require this step. After an additional 5-10 minutes we assessed whether or not wraps were tightly wrapped around trunks. All wraps within both 4.25-inch pre-coiled wrap treatments remained tightly wrapped around trunks. All 8.5-inch uncoiled wraps unraveled and 40% of 8.5-inch pre-coiled wraps unraveled suggesting a modest benefit to coiling this length and that extra length is not beneficial. Following this experiment, we successfully used pre-coiled 4.25-inch wraps on 16-19 mm caliper maple and 8.5-inch wraps on 46-52 mm caliper oak tree trunks. We observed that repeated wrap installation (approx. ≥5 times) to the same location on the same day sometimes caused minor bark damage. Pre-coiled wraps of the correct length unraveled in the high humidity of day-time field experiments but remained tightly wrapped in evening trials under less humid conditions. To maintain the coil during storage, we protected wraps with paper, then secured them with a rubber band.
Trunk-boring pests are a significant threat to nursery crops. Despite the prominence of air-assisted sprayers, little research has been published about their coverage of tree trunks. We assessed spray characteristics of a Jacto A400/850 sprayer with the objective of determining the lowest spray rate that provided at or near 100% trunk coverage. Water sensitive paper (WSP) was wrapped around the trunks at two heights in an external row and the middle row of a 3-row block of red maples (Acer rubrum) to assess coverage. Assessments included 15 trials with application rates from 65 to 244 GPA at 1.5 and 2.5 mph tractor speeds. Travel Speed: Spraying at 108 GPA and 112 GPA achieved ≥95% coverage when traveling 1.5 mph with windspeeds less than 1.5 mph. Spraying 112 GPA at 1.5 mph provided 96% coverage on wraps at both heights despite a maximum (unsustained) windspeed of 3.9 mph. Increasing the travel speed to 2.5 mph reduced the spray rate to 68 GPA and coverage to 79%. Spraying 244 GPA when traveling 1.5 mph provided 95% coverage. Increasing the travel speed to 2.5 mph decreased the rate to 146 GPA, and yielded coverage of 97%. Spraying 146-224 GPA with 1.0 mph average windspeed or less yielded ≥95% coverage in all four trials. Wind Speed: When traveling 1.5 mph and spraying 108 GPA with an average windspeed of 1.3 mph, 96% coverage was achieved. Coverage was reduced to 88% when the average windspeed increased to 2.5 mph. Stakes: Trees were secured using 1-inch stakes installed 3 inches from the western face of each trunk. The western face of wraps at 9 of 12 locations had coverage equal to or greater than that of the total wrap in three trials with less than 1.3 mph average windspeed. Row: In 10 trials, there was ≤2.5% difference in coverage between external and middle rows. However, in 5 trials the middle row had greater coverage by at least 6%. Spraying 109-112 GPA can provide near complete trunk coverage under low wind speeds. Higher spray rates can overcome high wind and travel speed, but are undesirable given the potential for drift and waste. Neither presence of a stake nor middle row position equates to worse coverage. Trees in the middle row may benefit from being equidistant from the sprayer as it travels down both driveways. These results provide a framework for future trunk coverage tests utilizing variable-rate technology.
Weed control in woody ornamental container production is one of the most expensive inputs in production. Preemergent herbicides, mulches and hand labor are all methods of delaying, impeding, or removing weeds that will negatively impact the growth and aesthetics of the produced container plant. One method gaining popularity in Central Florida to reduce weed competition is the use of rice hulls (RH) as a mulch. Effective mulches will reduce the amount of weed competition plants face. Rice hulls are a byproduct from the rice industry and deemed a disposed waste. RH are applied by hand in a layer of about 0.5 to 1 inch deep and dry out in a relatively quick manner. Growers anticipate that RH reduce the costs of weed competition and hand labor from weeding operations. This research investigated the economic cost of RH and benefit of RH mulch in terms of weed growth reduction.
Liverwort (Marchantia polymorpha L.) is a nonvascular, chlorophyll-containing, primitive, spore-bearing bryophyte. It is one of the major weed problems in container nurseries and greenhouse operations as it competes with the ornamental plant for resources within the container. Application of herbicides is a major component of any weed control program in ornamental production systems. There are limited herbicides labeled for liverwort control in greenhouse container production. A greenhouse experiment was conducted to evaluate the effect of various organic and synthetic herbicides on controlling liverwort growth. The herbicides were applied to nursery containers filled with standard substrate and amended with controlled release fertilizer for assessing the post-emergent liverwort control. Organic products namely Avenger, Scythe and WeedPharm were applied at 1X and 2X rates. Synthetic herbicides – Glyphosate, 2,4-D and Indaziflam were applied at 1X, 2X and 3X rates. Control set without any herbicide application was included as well. Percent of substrate surface covered by liverwort thalli was visually estimated bi-weekly until 16 weeks after first treatment. Fresh biomass of the thalli in each pot were also recorded at the end of the experiment. The experiment had six replications per treatment, and they were arranged in a randomized complete block design. For both the synthetic and organic herbicides, there was significant interaction between the type and rate of herbicide applied. The herbicide treatments were significantly different amongst each other and from the control. Out of various organic herbicides applied, all the herbicide treatments were able to limit liverwort coverage under 30% as compared to control (98%). WeedPharm and Scythe application at 2X and Avenger application at 1X rates recorded minimum liverwort fresh biomass. In the synthetic herbicide treatments, Indaziflam at 2X and 3X rates had minimal liverwort coverage and fresh biomass at the end of the experiment. Hence, these organic and synthetic herbicides can be a promising component for an integrated liverwort control program in containerized ornamental production.
The ornamental crop industry is a billion-dollar industry in the United States. Controlling weeds is a big challenge, as they can compete with ornamentals for soil, nutrients, water, light, and space by affecting the desired quality of ornamental crops like leaf and flower quality and color as well as proper growth. Weeds can also harbor insects, pests, diseases, and pathogens resulting in further reduction of market value. Due to greater genetic diversity and physiological plasticity, weeds are more likely to be able to adapt to a changing environment or climate. Increased atmospheric carbon dioxide (CO2) level can cause fertilization effect in C3 plants resulting in higher growth rates. Conversely, C4 plants are less likely to exhibit increased growth responses to elevated CO2 levels, as carbon dioxide fixation becomes saturated for them at around 360 ppm. So, ornamentals could gain a competitive advantage over many of the major weed species under elevated CO2, as many of the world’s ornamental crop species are C3 plants and many of the major weed species are C4 plants. But in reality, the scenario is different because other factors such as changes in herbicide efficacy and the ability of weed species to out compete ornamental species may come into play and limit this advantage. Plants that are grown in CO2-enriched environments often develop high concentrations of starch in leaves and greater total leaf area and biomass which can cause a dilution effect on herbicides. Additionally, C3 plants have been shown to have decreased stomatal conductance and increased leaf thickness in elevated CO2 which may also limit foliar uptake of herbicides. Environmental factors such as temperature, precipitation and relative humidity influence the efficacy of herbicides. There are studies that have reported decreased herbicide efficacy for control of annual and perennial weeds in elevated CO2 environments in agronomic crops. But limited information is available on how change in climate can affect herbicide efficacies in ornamental production. Hence, the objectives of this research proposal are: Evaluating increased temperature and CO2 levels on growth and reproduction of two different types of container-grown ornamentals; Determining effects of temperature and CO2 rise on preemergence herbicide performances for controlling C3 and C4 weed species; Determining effects of temperature and CO2 rise on postemergence herbicide performances for controlling C3 and C4 weed species; Assessing adaptive features of weed species with the change in environmental factors.
Production of economically important horticultural crops in the world, especially in developing countries, is faced with major challenges, including pests, and diseases. As a result, producers rely heavily on excessive use of synthetic pesticides, which often leads to negative impact to the environment, human health, and pesticide resistance. There is a need to develop environmentally friendly products to manage pests and diseases to increase crop yield, quality, and nutrition. Research was conducted in Rwanda to develop “EZA”, a new pesticide acting as an insect repellent, made of essential oils from local invasive plants such as Lantana camara, Tagetes minuta, and wastes of chili pepper and garlic. EZA was tested on tomatoes and mangoes under field conditions to manage several insect pests, including armyworms, fruit flies, thrips, and diseases such as tomato late blight caused by Phytophthora infestans. Results showed that EZA was effective in controlling insect pests, providing control of thrips and tomato late blight at the rate of 90% on 5 tomato plants where applied. Furthermore, tomato yield was increased by 40%. Information from this study demonstrates that EZA could significantly benefit horticultural crop producers, especially smallholder farmers in developing countries such as Rwanda, to effectively manage insect pests and diseases and the increase of crop yield.
The issue of soil salinity as a major cause of poor soil health and crop yield loss has been of growing concern as climate change contributes to its effects. The objective of this research was to study the impact of increasingly saline soils on the relationship between grafted watermelons and yellow nutsedge, one of the major weeds in watermelon plasticulture. The seedless watermelon cultivar Melody was grown in a field after being grafted onto the C. maxima hybrid Carnivor and the C. amarus cultivar Carolina Strongback in addition to both a self-grafted and ungrafted control. The field was divided into four rows, which were irrigated with 0, 10%, 20%, and 30% dilutions of sea water for the duration of the experiment. A weed count was performed after one month and three months of irrigation. This demonstrated that salt had a significant effect on the total weed count at high concentrations, however the weeds demonstrated a much greater resistance to salt treatment than the watermelons in this trial. Based on this data, it is possible that salt intrusion events can contribute to increased weed related yield loss in watermelon crops.
Can Multi-species Cover Crops and Beneficial Microbes be Utilized for Soil Borne Pathogen Management in Watermelon? - Sukhman Kaur Evaluation of Celery Breeding Lines and Commercial Cultivars for Resistance to Fusarium oxysporum f.sp. apii Race 2 and Race 4 - Christopher Greer Directed Energy System: A Non-chemical Approach for the Management of Nematodes, Pathogens, and Weeds in Nurseries - Tatiana Benedetti Sweetpotato-associated Virome in Mississippi - Sead Sabanadzovic Evaluation of Insecticide Application Plan to Manage Thrips for Sweet Onions in Texas - Subas Malla Are selective insecticides compatible with Bemisia tabaci biocontrol efforts in controlled environments? - Arash Kheirodin Plants Under Regulation; A North Carolina Perspective - Jarred Driscoll
Watermelon is highly susceptible to soil borne pathogens, typically Fusarium oxysporum sp. Niveum (FON) that can lead to a yield loss of upto 60-80%. Out of the four pathogenic races of FON, race 2 is more prevalent in the Southeastern US on more than 60% of watermelon fields. Cover crops are known for improving soil health, diversity, and abundance of microorganisms, and reported to decrease Fusarium wilt (FW) disease severity by up to 20-60%. However, previous studies have only evaluated single species cover crops for its impact on FW in watermelon whereas for ecosystems services, multi-species cover crops are recommended. A greenhouse and field study were conducted with aims to determine the effects of multi-species cover crops and beneficial microbes in controlling FW in watermelon. The cover crop mixtures included in the studies were, mixture A: rye, oat, Austrian winter pea, crimson clover, hairy vetch; mixture B: oat, wheat, crimson clover, radish, turnip. The field study was conducted at two locations in upper coastal region of South Carolina. Periodic cover crop biomass was taken. At location one cover crop mixture A accumulated a fresh biomass of 1017.50 tons/ha as compared to mixture B (907.16 tons/ha), at 97 days after planting. On the other hand, at second field site, mixture A accumulated fresh biomass of (349.6.4 tons/ha) and fresh biomass weight of mixture B was (153.59 tons/ha) at 120 days after planting. This could be due to more sandy and poor soil conditions at second field site. Further we will evaluate the impact of different treatments on FW disease severity index, watermelon fruit yield and fruit quality parameters.
Fusarium wilt of celery, caused by the soil-borne pathogen Fusarium oxysporum f. sp. apii (Foa), has been a persistent challenge for celery growers in California. Two races of the pathogen are documented in California. Foa race 2 was described in the 1970s and is widespread throughout celery-growing regions of California, typically causing yellowing and stunting of established plants, resulting in failure to produce marketable heads. Foa race 4 was identified in Ventura County in 2013 and by 2022 had displaced race 2 as the predominant race causing celery losses in Ventura County. Foa race 4 is more aggressive than race 2, often causing plant stunting and death within weeks after planting, particularly if soil temperature is 22ºC or higher. In support of celery breeding programs, USDA and University of California developed a collaboration to conduct resistance evaluation field trials. Trials were conducted in two coastal California locations naturally infested with Foa in 2022 and 2023: Santa Maria (race 2) and Camarillo (race 4). Cultivars and breeding lines from private companies and public germplasm collections were evaluated in replicated field plots. Plant mortality was assessed, and soil temperature was recorded during the growing season. At harvest, disease severity of internal symptoms of Fusarium wilt were scored from 0 (no visible symptoms) to 5 (severe crown decay) for a subset of plants from each plot. Each celery entry was assessed for petiole length, weight, petiole greenness, cracking, bolting, ribbiness, pithiness, and suckering for a subset of plants from each plot. At Santa Maria in 2022, there was minimal plant mortality, but most entries appeared susceptible with disease severity scores ranging from 2.0-3.6, indicating vascular symptoms in roots and crowns. Many entries did not produce marketable celery due to stunting. Entries exhibiting the most tolerance to Foa race 2 had disease severity scores of 0.1-0.7 and produced the heaviest stalks with the longest petioles. At Camarillo in 2022, daily mean air temperatures during the two weeks after planting were 24 to 27ºC, likely promoting rapid disease development of Foa race 4 and severe early decline in susceptible entries. Six weeks after planting, 23 of 42 entrees exhibited 80-100% plant mortality. However, five entries had disease severity scores of 1.0-1.5 and less than 15% mortality. These more tolerant lines produced marketable celery. These results contribute to the development of Foa-resistant breeding lines and inform growers about the performance of cultivars in local conditions.
Oregon leads the United States in the production of several ornamental nursery products including shade trees, conifers, and flowering trees. Soilborne pathogens and weeds are major constraints to the production of tree seedlings for the ornamental industry. Failure to control pathogens can result in seedling death or unintentional distribution of infected nursery stock while failure to control weeds can lead to competition with seedlings for water and nutrients. One of the primary ways to control soilborne pathogens and weeds is through pre-plant fumigation with methyl bromide. The use of this chemical is detrimental to the environment and human health, making it urgent to develop safer alternatives. Our long-term goal is to discover new ways to manage nematodes, soilborne pathogens, and weeds that will reduce reliance on pesticides and soil fumigants and be safer for the environment. Directed Energy System (DES) has been developed as a novel application technique, which generates pulses of electricity capable of killing nematodes, pathogens, and weeds. Controlled experiments were conducted against Meloidogyne chitwoodi, Phytophthora cinnamomi, and Cyperus esculentus to determine the electrical parameters required to kill each organism. Preliminary data demonstrated that the energy required to kill 90% of M. chitwoodi eggs was 23.4 J/cm3 of soil and for C. esculentus nutlets the energy for reduce weed growth by 50% ranged from 55 to 116 J/cm3 of soil.
Sweetpotato (Ipomoea batatas; Convolvulaceae) is an economically important specialty crop with an overall U.S. production valued at more than $720 million (2020 data, USDA-NASS). Even though virus infections are a major constraint to the sweetpotato industry across the United States and around the globe, organized studies have not been conducted to understand virus diversity and incidence. Therefore, an objective of a transdisciplinary multistate, Specialty Crop Research Initiative (SCRI), CleanSEED Project is to characterize viruses associated with sweetpotato production in major producing states. To that aim, 25 different locations/production fields in Mississippi were surveyed during the 2023 production season to collect symptomatic foliar tissue for total RNA extraction. The detection and identification of viruses of sweetpotatoes was based on a high-throughput sequencing approach on an Illumina platform utilizing 2x150 nt pair-end methodology, followed by computational analyses of billions of raw sequence reads. The four potyviruses, considered of major economic importance for the crop, were prevalent in the state and frequently occurred in mix infections. Furthermore, a few other viruses with possible hosts different than plant, were associated with plants analyzed in this study. This research was supported by the intramural research program of the U.S. Department of Agriculture, National Institute of Food and Agriculture, Specialty Crop Research Initiative, accession no. 1029242.
Thrips is an important pest of onions that not only reduces yield and quality but also transmit Iris Yellow Spot Virus. The study’s objective was to evaluate different chemical application plans to manage the thrips population in onions. The study was conducted in a split plot design with variety as a main plot and chemical plan as a sub-plot with four replications at Texas A&M AgriLife Research and Extension Center, Uvalde, TX during the 2022-23 season. The variety factor had three levels – Hornet, Mata Hari, and Don Victor. The chemical plan factor also had three levels – weekly application, action threshold (1 thrips per leaf), and control. Although the insect population was low, in general, for the season, the weekly application and action threshold treatments had a lower number of thrips per leaf than the control treatment. The numbers of chemical applications for the weekly application and action threshold were six and three, respectively. The results indicate that growers would save input costs if followed by the action threshold chemical plan. The trial will be evaluated in the 2023-24 season to validate results from the first season.
Generalist predators are known for their significant contribution to suppression of major crop pests in controlled environments and beyond. Given that insecticides are one pillar of many Integrated Pest Management (IPM) programs, their compatibility with biocontrol efforts is essential for developing a successful IPM program. Knowledge gaps persist regarding selective insecticides' non-target impacts on whitefly natural enemies that can jeopardize its biocontrol efforts. In this study, we exposed adult predators to commercially available insecticides (Cyantraniliprole and Pyriproxyfen) using multiple laboratory approaches to assess their effects on survivorship, predation, and changes in prey selection in response to insecticides. Two major whitefly predators were evaluated including, Hippodamia convergens (Coleoptera: Coccinellidae) and Geocoris punctipes (Hemiptera: Geocoridae), to estimate survivorship and consumption of whitefly nymph, Bemisia tabaci (Hemiptera: Aleyrodidae). Our result indicates that while pyriproxyfen had a negligible effect on the predators, cyantraniliprole exposure directly affected H. convergence by reducing survivorship duration and indirectly influenced both predators by reducing prey consumption and altering prey preference. Overall, pyriproxyfen demonstrated minimal impact on predators, while cyantraniliprole adversely influenced mortality and indirect foraging effects under controlled laboratory conditions. Hence, our findings highlight that even highly selective insecticides could have a sub-lethal impact on natural enemies, jeopardizing their contribution to pest control, and warranting future efforts to better integrate them into IPM programs.
State and federally regulated weeds pose significant challenges to agricultural economies worldwide, impacting crop yields, production costs, and overall farm profitability. Some estimates have their economic impact upwards of $30 billion dollars annually. Regulated plants can encroach upon public and private property, and cultural and recreational areas, which not only diminishes their aesthetic appeal and usability, but also displaces other native plants and animals. State and federal regulatory agencies operate within a legal framework for setting rules that allow for the control of regulated plants. Regulatory rules apply measures that help preserve these public and private spaces by addressing infestations of noxious plants. Management strategies of active infestations can range from controlling future or current spread to full on eradication. While eradication of a noxious plant may be the gold standard to strive for, it is also the most time consuming and costliest strategy. Often, two commonly employed solutions, aside from eradication, are; either managing or controlling an infestation. Managing is where the infestation isn’t increasing in geographic area. The periphery is fought to limit further spread. Controlling an infestation goes beyond managing, where a push is made to reduce the geographic area and steers the infested area toward an eradication track. The more stringent (eradication) a strategy becomes, the higher the cost and the longer it will take. The classic invasion curve describes this situation perfectly where the longer an infestation goes before it is identified, the more expensive and longer it will take to eradicate, if at all. Chemical applications, IPM and cultural control mechanisms are used to fight active infestations. Other tools in the regulatory tool bag include inspection of agricultural commodities and issuance of phytosanitary certificates, nursery inspections and certification, active survey and the use of quarantines and limited research permits. North Carolina has multiple active projects working towards eradication and control. Witchweed (Striga asiatica) populations have been present in NC and SC since its introduction in 1955. Witchweed, if left unchecked, has the potential to devastate the midwestern corn belt, which was the primary reason for its regulation. At that time North Carolina had approximately 400,000 infested acres. Today we have 2,000 infested acres. Other noxious weeds on the eradication path are wooly frogsmouth (Philydrum lanuginosum) and yellow floating heart (Nymphoides peltata). Both species have been aggressively treated in their limited distribution within the state.
