ASHS 2024 Conference

Evaluation of Plant Growth Regulators on Sweetpotato Slip Propagation - Kerington Bass
Effects of a Cytokinin-Containing Biostimulant Applied at Different Phenological Timings on Almond (Prunus dulcis) Yield - Orlando Tapia
The Application of a Cytokinin B-Mo-based Product Influences the Source-to-Sink Dynamics and Non-Structural Carbohydrate - Mayra Toro Herrera
PGR applications to reduce HLB-associated preharvest fruit drop in Sweet Orange - Tripti Vashisth
Ethephon Effect on Blooming of Three Southern Highbush Cultivars - Lilian Carcamo
Development of a Tissue Culture Approach for Doubling the Ploidy Level of Southern Highbush Blueberry Varieties - Emily Walter

Producing sweetpotatoes involve several phases presenting unique challenges, most notably during transplanting. Sweetpotato slips, used for asexual reproduction, have non-uniform characteristics, making transplanting difficult. Additionally, the transition from a greenhouse to a field condition poses environmental risks and challenges, resulting in low transplant survival rates. A high slip mortality rate creates economic and logistical problems for producers. Plant growth regulators (PGRs) have been found to induce lignification or thickening of cell walls, which can alleviate environmental stresses in other crops; however, their impact remains unexplored in sweetpotato slips. Therefore, a study at Mississippi State University was conducted with the primary goal to enhance sweetpotato slip quality and improve transplant establishment rates. The study involves two greenhouse trials to identify the most effective PGR types and concentrations, and two histology trials to illustrate the effects of PGRs on sweetpotato slip lignin and cell wall. The greenhouse trials utilize a randomized complete block design to assess four different PGR types and thirteen concentrations on three replications of sweetpotato slips with 38 subsamples per treatment per replication. Data on plant height, stem diameter, number of nodes, SPAD, leaf area, and dry weight and fresh weight of the slips and roots were collected to determine the effects of PGRs on the plants. The histology trials included the same PGR treatments and concentrations to the slips. The slips were then collected, cross-sectioned, stained, and evaluated and measured under a microscope. The study proved that PGRs do have an effect on sweetpotato slips, by altering plant height, dry weight, and fresh weight, while not impacting the number of nodes. Thickening of the cell wall was also observed in slips treated with certain PGRs and it is hypothesized that this thickening of cell walls can contribute to reduced slip mortality when transplanting greenhouse produced slips to the field.

Almond (Prunus dulcis) is one of the most important crops in California. This commodity represented an economic impact of over 3.5 billion dollars for the state in 2022. During that year, 1,630,000 million planted acres were reported. In 2023, this number dropped by 74,000 acres, continuing the trend of decline due to numerous challenges that the industry has been facing. These include volatile prices, high input costs, reduced water allocations, climate unpredictability, and high temperatures during key phenological timings. The almond crop is highly sensitive to environmental factors, and photosynthetic rates can significantly decrease when temperatures reach 94F, heat levels are easily reached during the hot summer months in California’s production areas. To this matter, significant contributions are needed to support the industry. There are over 700 peer-reviewed scientific publications that evidence the benefits of using biologicals, which include plant biostimulants (PBS), in agriculture. It has been shown that season-long exogenous applications of cytokinin-containing PBS can support higher marketable yields. It is important to understand the physiological timings in which these applications have the most impact, in terms of maximizing the yield and quality potential. In 2023, a randomized complete-block design (RCBD) study was conducted on 5th leaf Var. Nonpareil in California’s Central Valley. The objective was to evaluate the yield and quality effects of an application of X-CyteTM, a 0.04% cytokinin-containing biostimulant registered for use on almonds in California, at different standalone phenological timings. These included early bloom, full bloom, petal fall, may spray, and hull-split. The trial consisted of six four-tree replications per treatment. Yield and quality data were subjected to a one-way ANOVA using IBM® SPSS® Statistics, and means were separated using Tukey’s HSD. The standard grower practice (SGP) produced 1801.5 marketable pounds of kernel meat per acre. X-Cyte™ treatment yields of 1845.16, 2140.16, 2215.66, 2137.67, and 2318.33, were observed for early bloom, full bloom, petal fall, may spray, and hull-split timings, respectively. Statistically significant differences were observed (p-value: 0.003). The hull-split and petal fall timing applications represented the higher yield increases (516.8 and 414.2 lbs/A, respectively) overall, compared to the SGP. It has been documented that taking place at these timings are key phenological stages deemed as major contributors to the components of yield: fruit set and nut fill. Significant differences in kernel size were not observed (p-value: 0.549). These findings further support and help fine-tune the use of biologicals and PBS in agricultural production systems.

Understanding the sink-to-source relationship on leafy crops offers valuable insights into optimizing resource allocation for enhanced plant growth and quality. Variations in growth rates and carbon pools across individual leaves or groups of leaves at similar developmental stages allow us to understand the plant strategies of carbon allocation and partitioning. We hypothesized that products that enhance the carbon source-to-sink relationship during leaf development can lead to increased growth and dry matter accumulation. This project aimed to determine if the exogenous application of a cytokinin and B-Mo-based product during leaf development would impact carbon source-to-sink relationship and, hence, influence plant growth and quality. The experiment was a complete randomized design with two treatments consisting of a negative control and the application of the product twice during the growing cycle. The experimental unit consisted of a deep-water culture reservoir with three lettuce plants. Destructive sampling was conducted at five sampling points. At each sampling point (n=4 per experimental run), the phenological stage was determined, and root and shoot length and dry matter, leaf length, width, area, and non-structural carbon and chlorophyll contents were measured. This data was used to estimate growth rates. Results indicate that the cytokinin and B-Mo-based product increased the number of true unfolded leaves by 1 ± 0.4 and the overall size of the lettuce head by 9%. The treated lettuce reached a marketable size four days earlier than the control treatment. Statistically significant differences were observed in the shoot and root dry matter accumulation and foliar length and width at some sampling points. Some of the growth indices indicate an increase in leaf surface area investment and enhanced conversion efficiency of assimilates into biomass in plants treated with the product. Plants exhibiting these alterations had higher sucrose and total soluble sugar content. There was a noticeable pattern of higher concentrations of non-structural carbohydrates, proteins, and amino acids in the leaves compared with the roots across all plants and treatments. Overall, our study on using a cytokinin and B-Mo-based product to strengthen the source-to-sink relationship during the development of a leafy crop provides new insights into non-structural carbohydrate metabolism and the role of CKs, B, and Mo in generating a high-quality plant in a shorter timeframe.

The Florida citrus industry has seen a steady decline in production since the arrival of Huanglongbing (HLB), or citrus greening disease, in Southern Florida in 2005. Following infection, trees experience a steady decline in health and productivity. HLB has since spread throughout all of Florida’s citrus producing regions resulting in nearly 100% infection rates in traditional field settings. Lamentably, no cure has been found for HLB, so research efforts have focused on mitigating the symptoms associated with this disease. Among the myriad of symptoms associated with HLB, the increased rates of mature fruit (preharvest fruit drop) is a major concern for growers. Not only do more fruit drop in HLB-affected trees, but fruit also begin dropping earlier in affected trees as well. This loss of mature, and potentially marketable, fruit in the months leading up to harvest represents a visual loss of revenue for the growers. The authors have previously reported that the likelihood of a fruit to drop during preharvest fruit drop is related to the size of that fruit; the relatively smaller fruit on the tree are more likely to drop during the preharvest fruit drop window. As plant growth regulators (PGRs) have had promising results in preventing fruit drop in many crop species, the efficacy of PGR applications in reducing preharvest fruit drop was evaluated. Thirty small and thirty large fruit were tagged on four 12-year-old ‘Valencia’ on ‘Swingle’ rootstock trees. Small fruit were those that were a ½ standard deviation below the average fruit size for that tree whereas large fruit were those that were a ½ standard deviation above the average. Ten of the small tagged fruit and ten of the large tagged fruit were then dipped into ProGibb® (33 ppm Gibberellic Acid [GA]), Citrus Fix® (106 ppm 2,4-Dichlorophenoxyacetic Acid [2,4-D]), or left untreated (control). Citrus Fix® improved retention in both small and large fruit whereas ProGibb® only improved retention in the large fruit. As GA prevents drop by delaying the senescence process, the lack of effect in the small fruit may suggest that they have already entered the senescence process. To further explore why the small and large fruit differ in their likelihood to drop and why they respond differently to PGR applications, additional biochemical and molecular analyses are underway.

Spring frost is the primary cause of yield reduction in southern highbush, representing a significant challenge to blueberry production in the southeastern United States. Plant growth regulators are used as aids in different agricultural industries to either advance or delay growth and development process. Ethephon influences fruit set, size, and yield and has also been used as a tool to delay bloom in order to avoid freeze damage. This study examined the efficacy of ethephon to delay flower bud growth stages in three Southern Highbush Blueberry cultivars (‘Farthing’, ‘Georgia Dawn’, and ‘Kee Crisp’). Ethephon was applied at different concentrations of 200, 400, and 800 ppm, and a control treatment water/surfactant was also included. Flower buds were visually assessed from January until March. No relevant results were found for ‘Farthing’; however, for ‘Georgia Dawn’ and ‘Kee Crisp', ethephon at 800 ppm had the highest effect on delaying blooming development compared to the control. These results suggest that ethephon might delay flower bud growth stages in Georgia Dawn and Kee Crisp, offering potential advantages in reducing susceptibility to spring chill injury.

Increased consumption of blueberries has led to a prominent rise in demand. However, Georgia blueberry production is limited by challenges including short orchard life of southern highbush (SHB; tetraploid) and fruit quality issues associated with rabbiteye (RE; hexaploid) varieties. Interspecific hybridization can bring in beneficial alleles to improve the local adaptability and fruit quality of commercial varieties. Many of the wild blueberry germplasm with valuable soil adaptability and fruit quality traits such as V. fuscatum are diploids. Heteroploid crossings between SHB and diploid wild blueberry were shown to have a very low level of success. Ploidy induction through tissue culture is promising to circumvent the ploidy barrier and improve the efficiency of wide-hybridization. The objective of this research focuses on developing a ploidy induction protocol using two SHB varieties ‘Emerald’ and ‘Rebel’. SHBs previously initiated in tissue culture, were treated with 0%, 0.02% and 0.2% colchicine. SHBs were segmented into single and double node segments and put into woody plant medium (WPM) culture media containing either 6-(γ,γ-Dimethylallylamino)Purine (2iP) or trans-Zeatin. The treatments, along with non-treated control, were grown in a growth chamber of 26°C with 16/8 day and night cycles. The number and length of new shoots were recorded 35 and 50 days after treatment (DAT). Significant longer axillary stem growth was observed in the non-treated control compared to that of colchicine-treated segments for both SHBs indicating the suppressive effect of stem growth from colchicine treatments. Several Octo- and mix ploidy-shoots of ‘Emerald’ and ‘Rebel’ were identified among colchicine-treated SHB explants after ~ 21 weeks using a flow cytometer. Both levels of colchicine treatments generated octoploids. These new synthetic octoploid blueberries will be useful to cross with SHB and RE blueberries. The established ploidy induction protocol will be utilized to double the chromosomal levels of diploid V. fuscatum species and make them cross-compatible with SHB varieties.

A Snapshot of Nursery Container Substrate Prices in Tennessee - Amy Fulcher
Suppression of Stem Elongation of UV-B Treatment Timing and Intensity on Tomato Scion and Rootstock in Plant Factory with Artificial Lighting - Dongcheol Jjang
Effects of Nitrogen on the Nodulation of Ceanothus velutinus - PRAKRITI NEPAL

In container nursery production, the potting substrate serves as the foundation of the crop, providing essential nutrients, aeration, and moisture retention. A well-chosen substrate is crucial for optimizing plant health and growth, and ultimately influences a nursery’s economic viability since substrate is estimated to be 13% of the total variable costs of 3-gallon production. Our objective is to determine the cost of common potting substrate components. The study goal is to identify opportunities for nursery producers to reduce costs and increase profits by optimizing their substrate components. Email surveys supplemented by interviews were used to collect data from six Tennessee container nursery producers. All growers were within a 117-mile radius of McMinnville, Tennessee, and provided the prices they paid in the last 12 months for the primary components of their potting substrate. Delivery fees and fuel surcharges were not considered in the cost when these expenses were itemized. However, one producer’s prices included delivery expenses. Participating nursery producers self-identified as having 100 (66.7%) acres in container production. Growers in this case study paid an average of $19.07 (SD=$5.53) per yard3 for pine bark; however, the prices ranged from $14.53 to $29.00 per yard3. In general, smaller producers paid more for pine bark. Sand ranged from $40.50 to $49.95 per yd3. Nursery producers paid $1.12 to 1.32 per pound for controlled release fertilizer (CRF), an input estimated at 5% of total variable costs. Therefore, some growers paid 18% more for CRF than others. Growers paid from $0.01 to $0.11 per pound for lime. Tennessee nursery producers were paying on average $66.79 per cubic yard for wood fiber-based substrate and vermicompost, 250% more than the average cost of pine bark but just 46% of the market price for peat. These preliminary data show 1) individual nurseries pay a range of prices for the same potting substrate components, and 2) the relatively high cost of peat replacements, i.e., wood fiber and vermicompost. The data highlight the range of prices being paid for CRF and its relative expense, underscoring the opportunity for growers to reduce costs by optimizing their use and placement of CRF. Additional research is needed to more broadly sample nurseries for these data and determine the influence of nursery size on substrate component costs. cparwutcakwt8uvpamtb

This study aimed to determine the optimal conditions of UV-B exposure for regulating the growth of tomato grafted seedling in Plant Factory with Artificial Lighting by investigating growth characteristics, rhizosphere development, and chlorophyll fluorescence of seedlings. Tomato scion and rootstock were used in the experiment. UV-B treatment timing was divided into three stages from sowing to grafting. UV-B intensities were set at 1.44, 2.88, and 5.76 kJ·m−2·d−1. Results showed that morphology of plants did not exhibit significant differences up to 2.88 kJ·m−2·d−1 for tomato scion and rootstock. However, side effects such as leaf wilting were observed at 5.76 kJ·m−2·d−1. The length of hypocotyl, which is closely related to scion and rootstock suppression of stem elongation, was shortest when treated with 5.76 kJ·m−2·d−1 during the mid-growth stage across all treatment. Interestingly, rhizosphere characteristics such as root volume, surface area, and average root diameter showed improvement trends regardless of treatment timing when exposed to UV-B at 1.44-2.88 kJ·m−2·d−1. Quality indicators of seedlings showed best when 2.88 kJ·m−2·d−1 during the late-growth stage. Comparisons of chlorophyll fluorescence parameters revealed no significant effects of UV-B treatment on cucumber seedlings and grafting except for PIABS. However, tomato seedlings and grafting exhibited significantly reduced FV/FM and DIO/RC at late-growth stage when exposed to 5.76 kJ·m−2·d−1. Therefore, it is concluded that utilizing UV-B in the range of 1.44-2.88 kJ·m−2·d−1 during cucumber and tomato scion and rootstock production in Plant Factory with Artificial Lighting could minimize plant damage while expecting to suppress grafting effects.

Ceanothus velutinus, commonly known as snowbrush ceanothus, is a nitrogen-fixing species native to North America. It plays a vital role in ecosystem by improving soil fertility through nodulation, a symbiotic process with bacteria that fixes atmospheric nitrogen. The purpose of this study was to identify the effects of various nitrogen concentrations on the nodulation and plant morphological and physiological responses. Ceanothus velutinus seedlings were transplanted in calcined clay and inoculated with 30 mL of soil containing Frankia. Seedlings were treated with 0.0 to 8.4 g·L-1 of controlled released fertilizer (CRF, 15N-3.9P-10K) or a nitrogen-free nutrient solution supplemented with or without 2mM ammonium nitrate (NH4NO3). Plant growth and photosynthesis increased linearly or quadratically along with the increasing CRF application rates with a notable increase observed at 4.2 g of CRF. Nodules were observed only in plants receiving 0.0, 0.3, 0.5, 1.1, or 2.1 g of CRF. However, the number of nodules formed in the treatments was too small to analyze statistically. The study indicates that while CRF significantly boosts C. velutinus growth, nodulation and nitrogen fixing capacity of the plant remains unknown. Further investigation is needed to determine the effect of nitrogen on the nodulation of C. velutinus using peat-based soilless substrate.

Effects of Off-Season Winter Cover Crops and In-Season Nematicide Application on Plant-Parasitic Nematodes - Abolfazl Hajihassani
Lessons Learned from Living Mulch Trials on Midwest Vegetable Farms - Connor Ruen
Evaluating Cover Crop Biomass and Roller Crimper Technology for Effective Weed Control in Vegetable Systems - Arianna Bozzolo
Fall Cover Crops to Follow Carrot Harvest on High Organic Matter Soils - Mary Ruth McDonald
Cover Crops For Vegetable Research Farms Need Nitrogen - Thomas Bjorkman
Insurance Industry Standards Over-estimate Yield Loss Due to Stand Reduction in Processing Sweet Corn - Charlie Rohwer
Combining Lasers and Distress Calls to Control Birds in Sweet Corn - Rebecca Brown
Pea-oat Green Manure and Reduced Nitrogen Rate Delay Maturity of Broccoli But Do Not Reduce Yield - Charlie Rohwer
Field Screening of Cabbage (Brassica oleracea var. capitata) Cultivars for Resistance to Black Rot - Manisha Kumari
Evaluation of Brassica Oleracea Genotypes in Terms of Agronomic Performance - Sotirios Tasioulas

In the Southeast United States, control of parasitic nematodes in vegetable growing systems has traditionally relied on soil fumigation before planting vegetables. However, new regulations on the application of fumigant pesticides and concerns about their toxicity to non-target organisms are compelling growers to adopt sustainable alternatives. This study examined the effects of winter cover crops and subsequent production of cabbage treated with a non-fumigant nematicide on root-knot (Meloiodgyne incognita) and stubby-root (Nanidorus minor) nematodes. Off-season treatments consisted of oilseed radish cvs. “Control” and “Image”, cereal rye cv. “Wrerens Abrussi”, oat cv. “Tachiibuki”, black oat cv. “Protex” and mustard cv. “Caliente”. In-season treatments consisted of an untreated check and the nematicide fluensulfone, applied through the drip irrigation system one week before transplanting cabbage into raised beds covered with plastic mulch. A weedy fallow treatment was also included for comparison. After growing cover crops and incorporating plant residues into the soil, M. incognita population density was significantly reduced only in plots where Tachiibuki oat was grown. None of the cover crops reduced the population density of N. minor. Nematicide application on cabbage significantly reduced M. incognita populations in plots previously grown with Tachiibuki and Pratex oats, and mustard compared to the untreated check. Similarly, the nematicide reduced the N. minor population density in plots previously grown with oats, mustard, and rye. The efficacy of fluensulfone on root gall severity of cabbage was significant only in the untreated check, with plots previously grown with Image radish having a significantly lower root galling than the mustard, rye, and weedy fallow. Nematicide application reduced root gall severity of cabbage in plots previously grown with radish, Tachiibuki oat, and rye compared to the untreated check. Growing cabbage after cover crops and using the nematicide did not impact cabbage yield compared to the untreated check. These results indicate that cover cropping with Tachiibuki oat and the use of non-fumigant nematicides appear to be effective for managing these nematode species.

In the Great Plains region of the United States, perennial clover living mulch is being explored for the potential benefits of reducing tillage, suppressing weeds, and supplementing soil. Perennial living mulch systems also have the potential to reduce the use of single-use plastic. Research on the use of perennial living mulch in vegetable systems has been limited in the Great Plans, and farmers have expressed interest in trialing this system to improve soil health and reduce erosion by wind and rain. Two vegetable farms, Haroldson Farms in Bruce, SD and Blue Sky Vegetable Company in Worthing, SD, have participated in the on-farm trials since 2023. In collaboration with South Dakota State University, the on-farm trial collaborators were interested in using living mulch to control weeds and reduce the need for plastic. ‘Domino’ white clover (WC) (Trifolium repens), and ‘Dynamite’ red clover (RC) (Trifolium pratense) are the clovers that were selected for the on-farm trials. The clover struggled to grow with the lack of rainfall and was soon overtaken by weeds. Results quickly showed that the lack of moisture had a detrimental effect on the clover’s ability to compete and establish in walkways. A mixture of grasses and broadleaf were observed as the clover declined. Early moisture is essential for the establishment of clover living mulch and be used to its full potential. The planting method of frost seeding would be recommended for future trials to encourage clover germination and establishment before weeds get large enough to compete.

This study aims to evaluate the efficacy of roller crimper technology in tandem with various cover crop mixtures for weed management in coastal California's vegetable systems. The experiment was conducted at the Rodale Institute California Organic Center (34.220453, -199.108214) in Camarillo, CA. Twenty randomized plots 46 x 12 m were measured and assigned to either to a bare soil treatment or one of two cover crop mixes: oat (Avena sativa) hairy vetch (Vicia villosa), or oat pea (Pisum sativum), with cover crops terminated via conventional tillage using a disk (T) or using a roller crimper for no-till system (NT). Pumpkins (Howden variety) were direct seeded, and data on cover crop growth and weed pressure were collected at three time points: before cover crop termination, after cover crop termination and after harvest. At harvest, a subset of each plot was sampled to count and weigh pumpkins for crop yield assessment. Before termination, the total dry matter of cover crop biomass showed no significant differences between oat/peas and oat/vetch mixes. Oat/vetch exhibited lower weed biomass at 0.74 t/ha compared to oat/peas at 1.98 t/ha (0.8 t/a); bare soil plots had the greatest biomass at 21.35 t/ha. After termination (30 DAT), NT plots showed similar biomass production between oat/peas and oat/vetch. T plots displayed residues on the soil surface, with higher amounts in oat/vetch at 8.7 t/ha compared to oat/peas at 8.4 t/ha. Weed emergence after cover crop termination was comparable across all plots with cover crops, ranging from 1.24 t/ha to 2.22 t/ha, while bare soil exhibited higher weed biomass at 10 t/ha compared to plots with cover crops. After harvest (120 DAT), oat/vetch in NT plots showed greater biomass retention compared to T plots, as did oat/peas in NT plots. All plots experienced biomass reductions, with oat/peas T plots experiencing the most significant decrease at 61.5%. Oat/vetch mixture plots (T and NT) and bare soil had similar pumpkins production per hectare, outperforming oat/pea T plots in terms of fruit number and production per hectare. Oat/pea T plots exhibited decreased fruit weight compared to bare soil.

The high organic matter (muck) soils in the Holland Marsh, Ontario, Canada, are prone to wind erosion, especially in the fall and winter months. Good canopy coverage of ideally 30%, is important for protecting the soil and reducing soil erosion. Carrots are usually harvested in October. Cool temperatures at this time result in slow germination and growth of cover crop species. Field trials were conducted to assess the efficacy of various cover crops and methods for rapid establishment after carrot harvest. One approach to increasing germination and emergence is seed priming. Seeds of barley, oats, and triticale were primed by soaking for 24 hr in water (hydro-priming) or potassium nitrate at 5 mg L-1 (osmo-priming). Seed was dried for 24 hours and then seeded into pots placed in controlled environments at 5, 10 or 21°C. Priming generally resulted in faster germination and higher biomass especially at lower temperatures of 5 and 10°C. Primed and non-primed seed was seeded into high organic matter soil (50% organic matter, pH 6.9) on 17 Oct. and crop growth was assessed on 13 Nov. There were no advantages of priming in the field trials. Non-primed barley had high or higher canopy coverage (13%), plant counts and dry weight, compared to other species and primed seed. Barely was also grown as transplants with 2 seeds/plug and transplanted in the trial on 17 Oct. This treatment had higher canopy coverage (25%) and dry weight than seeded treatments. However, using barley transplants is not a cost effective option at this time. In a separate trial on an adjacent site, barley was over-seeded into standing carrots on 27 Sept. at 200 kg ha-1, and the carrots were harvested on 17 Oct. Barley and fall rye were direct seeded on 17 Oct. Pre-harvest seeding of barley resulted in significantly better establishment, canopy coverage and biomass, although all were low, maximum 12% coverage. There was a strong positive correlation between canopy coverage and biomass production across all trials. More research is needed on cover crops species and establishment methods.

On research farms on which vegetable crops are studied, there is often a need to aggressively maintain and improve soil health, while also keeping fields ready to be assigned to research projects. We tested a protocol for keeping a Northeast farm in an appropriate condition by alternating a winter cover crop of cereal rye and a summer cover crop of forage sorghum-sudangrass with no tillage. The alternating cycle was flexible for entry points when vegetable researchers finished with an experiment, as well as for exit points to make the ground ready for an experiment. Rye was sown in late September in Geneva, NY with a no-till drill and allowed to grow to anthesis in May. Sorghum-sudangrass was sown in mid-June with the no-till drill. We tested how much nitrogen fertilizer was needed to obtain a desirable amount of growth (3 tons/acre dry mater) in the sorghum- sudangrass. The trial was done in four fields using 0, 20, 40 and 60 lb N broadcast on the rye residue at planting. The highest rate is as much as our farm would agree to invest in a cover crop, but also below forage-crop recommendations. The biomass when growth stopped due to cold (Sept 18) responded strongly to nitrogen. Without nitrogen, the biomass was only 0.5 T/ac. At 60 lb/ac, the biomass ranged among fields from 2 to 4 T/ac. Nitrogen limitation was also assessed using a SPAD chlorophyll meter. The leaves in the 0, 20 and 40 lb/ac were yellow (SPAD 22-28), with the top N rate notably greener (SPAD 30-35). The fully green control had a SPAD value of 40. The cover crop rotation kept the field in a condition where is could be prepared to being a research project with about a month’s advance notice. However, to get sufficient growth of the summer cover crop, additional nitrogen is needed. This farm is on a high-fertility silt loam, but with low organic matter from repeated research trials. In that situation, at least 60 lb/ac of actual N is needed for the cover crops to meet biomass expectations.

Sweet corn is an important processing crop in the upper Midwestern United States. It can be insured for hail losses, but actuarial tables are based on field corn. The first step in developing accurate yield loss assessments is determining yield loss due to complete plant loss. To that end, we compared ear yield of sweet corn thinned to 75, 50, or 25% of a full population at three times throughout the growing season to control plots that were not thinned. We repeated this in three consecutive years at two locations, without irrigation or supplemental fertilizer. Average yield for control plots was 16.4–20.3 Mg•ha-1. Average yield losses due to thinning were generally less than currently-used actuarial estimates. For example, average yield of sweet corn when thinned to 50% of a full population at growth stage V3–V5 was 88–96% (95%CI) of full yield. The actuarial estimate is 78% of full yield, indicating greater resilience than expected. The number of tillers per plant was greater in all thinned plots, especially those thinned early in the season. Kernel recovery was unaffected by thinning treatment in one location and declined slightly at heavy thinning in the other location. Sweet corn actuarial tables should be different from actuarial tables based on field corn.

Red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) cause significant damage to sweet corn (Zea mays). Even minor damage can render ears unmarketable and the need to sort out damaged ears during packing increases costs for growers. Propane cannons and pyrotechnics have long been the preferred methods for preventing birds from damaging corn, but both methods create noise pollution and conflicts with farm neighbors. Automated laser scarecrows and automated recordings of bird distress and predator calls are two newer technologies for deterring birds from crops. We tested both technologies on a research farm in Kingston, Rhode Island and in commercial processing sweet corn fields in western New York in 2022 and 2023. All experiments used naturally occurring flocks of wild birds; flock size and species makeup varied between fields and over time. The automated laser scarecrows (LS) were designed and built by the URI Laser Scarecrow Project; they utilized a 50 mW 532 nm green laser with a beam diameter of 14 mm at the aperture and a dispersion of 4 mrad. Vertical and horizontal movement of the beam was randomized by a microcontroller. Bird Gard Super Pro units (BG) randomly played digital recordings of distress and alarm calls of red-winged blackbirds and European starlings and hunting calls of hawks and falcons. Data were collected as counts of damaged ears and converted to percentage of total ears for analysis. In Rhode Island the effect of laser scarecrow alone was compared to the effect of the laser scarecrow combined with the bird distress calls. In New York the two deterrent treatments were also compared to an unprotected control. In Rhode Island in 2022 bird damage averaged 20.7% with just LS and 7.1% with LS BG; the difference was significant at P

Cover crop biomass can provide nitrogen (N) to a sequential cash crop as a ‘green manure’, whether the N is sourced from the atmosphere or from the soil. For short-season vegetable crops in Minnesota, like transplanted broccoli, there is time for a cover crop to be grown before or after the main crop. Growing a pea-oat cover crop early in the spring, before broccoli, may increase the N available to the broccoli. However, immobilization of green manure N may reduce N availability at a time of high N demand in broccoli. In order to study N availability to broccoli provided by a spring-planted pea-oat cover crop mix, four reduced-rate nitrogen treatments were applied to two broccoli hybrids (‘Green Magic’ or ‘Gypsy’) after a spring-planted pea-oat cover crop was incorporated. Yield and maturity of broccoli were compared to broccoli grown without green manure and given a full nitrogen rate (170 kg N / ha). The fertilizer treatments included slow-release urea (139 or 110 kg N / ha), composted poultry litter with blood meal at ~110 kg N available / ha, and turkey manure applied with blood meal in the autumn before growing green manure and broccoli (~110 kg N available / ha). There was no reduction in total yield (7900 kg / ha) or marketability (>95%), but maturity was delayed by ~2 days for most treatments. A microbial inoculant (Nature’s Source®) applied to the soil at planting did not have a measurable impact on any response.

One of the most effective management strategies for controlling black rot (Xanthomonas campestris pv. Campestris (Xcc)) in cabbage (Brassica oleracea var. capitata) is resistant cultivars. The objectives of this research were to evaluate commercial and experimental cabbage cultivars for black rot resistance and determine yield potential, harvest maturity, and head quality. A field experiment with nine cultivars (1488, Capture, Celebrate, Cheers, Expat, Melissa, TCA-576, TCA-606, and TCA-607) was carried out during the fall season of 2023 at Hort Hill research farm on the University of Georgia, Tifton campus. ‘Cheers’ (commonly grown high-yielding cultivar), ‘Capture’, and ‘Expat’ (claims high resistance to black rot), and ‘Melissa’ (black rot susceptible Savoy cabbage) were used as checks for comparison with other F1 cabbages. Plants were spray-inoculated with Xcc (250 ml of 10^6 CFU/ml) at 5 and 7 weeks after transplanting. Treatments were arranged in a randomized complete block design with four replications. Relevant agronomic practices, such as irrigation, fertilization, and insect management, were implemented uniformly across all plots. Black rot severity was rated using a 1-9 scale, where 1 indicates the most resistant and 9 represents the least resistant (most susceptible) cultivar. The trial was harvested four times on the following dates:11/30/2023, 12/12/2023, 12/20/2023, and 01/03/2023. Black rot severity, total head counts and weights; and average head weight and height: and average core height, and width were statistically significant between treatments. ‘TCA-607’ and ‘Capture’ had the highest resistance to black rot disease, while ‘1488’ was the most susceptible. All other cultivars expressed moderate levels of resistance. In the first harvest ‘Cheers’ and ‘TCA-607’ had the highest total marketable head counts and weights, indicating early maturity. In addition, ‘Cheers’ and ‘TCA-607’ cabbage had the highest total marketable head counts and weight, followed closely by ‘TCA-606, ‘Celebrate’, and ‘1488’. ‘Cheers’ and ‘TCA-607’ had the highest average head height. Furthermore ‘TCA-607’ outperformed all the cultivars for the average head weight. Among all the cultivars ‘Melissa’ and ‘Expat’ performed the worst for total marketable counts and weights. Overall based on our trial, the experimental cultivar ‘TCA-607’ has the best combination of traits: best black rot resistance, highest yields, and biggest heads.

Plant growth performance of 35 different broccoli cultivars was assessed during the Fall season 2023 in terms of plant growth and head development in SW Florida. In particular, seeds of Brassica oleracea var. italica genotypes that were obtained from USDA, ARS, Plant Genetic Resources Unit (PGRU)

Multiple Modeling Approaches Reveal Temperature Dependent Germination Traits of Vegetable Varieties - Miro Stuke
Identifying Pollinators Present on Flowers of the Pawpaw Cultivars 'Sunflower' and 'Susquehanna' - Subas Thapa Magar
Molecular Assessment of Heat Sensitivity in Broccoli Flowering - Thomas Bjorkman
Morpho-physiological Response of Plectranthus amboinicus under Flooding and Drought Stress - Samuel Asiedu
Effects of Paclobutrazol, Progressive-raising Temperature and Spike-truncated Treatments on Phalaenopsis Join Grace ‘TH288-4’ - Yi Chien Lu

Crop seed germination is a critical factor in food production. Germination traits vary between different vegetables and between cultivars of the same vegetable. Traits such as germination proportion and the rate and uniformity of germination also contribute to the success of vegetable cultivars to regional temperature averages and regimes. Temperature is a major abiotic factor in seed germination, and selection of seed varieties suited for local temperatures is important to successful crop establishment. Here we aim to model the germination traits of several Korean and North American vegetable cultivars in relationship to temperature. We hypothesize that a model based on time and temperature will represent germination traits across multiple cultivars and species of vegetable. Additionally, we hypothesize that predicted germination traits will be similar within species but will vary between cultivars of the same species based on the regional temperature norms. Eleven vegetable cultivars including two corn, four radish, two pepper, and three onion, were germinated in growth chambers set at 5°C intervals between 5 and 40°C with a 12 hour photoperiod. Germination, defined by radicle emergence equal to the length of the seed, was monitored and recorded daily. Two modeling approaches were used. 1) A time to event model using the drcSeedGerm package in R was used to determine maximum germination proportion (Pmax), germination rate at 50% germination (GR50), and uniformity. 2) A 12-parameter compartmental temperature and time model was implemented, parameterized, and validated in the Cropbox modeling framework. Results show differing temperature responses in germination traits. Additionally, high uniformity was observed in most varieties within the optimal temperature range. The optimal temperature for germination was broad for the vegetable cultivars tested here, with a rapid decrease in Pmax at high and low temperature extremes, except in onions, which showed high Pmax even at 5°C, and a gradual decline above 25°C. All cultivars showed decreased Pmax at 40°C. A time to event model was able to predict germination traits in several crop species. The compartmental model was better equipped to handle heat induced seed degradation but was less parsimonious for determining germination probability and germination rate related parameters. Modeling crop germination traits can provide important context for selecting appropriate cultivars for local climates. A thermal time to event model and a compartmental model both provide potential frameworks for modeling germination traits of diverse vegetable species.

Pawpaw (Asimina Triloba) is a temperate species of tropical Annonaceae plant family native to the United States. They are small to medium-sized deciduous trees that bear unique and flavorful fruit. Pawpaw fruits are used in various culinary products such as jam, bread, ice cream, cookies, and even to produce brandy. Additionally, they contain antioxidants and acetogenins, which are currently being researched for their potential in cancer treatment. Fruit sets may be limited in some cultivars due to pawpaw flowers being protogynous and self-incompatible, blooming at various stages of development from late March to April. Consequently, the role of insects in pollination is crucial for increasing fruit production. To address this gap in research, this study aims to identify the different insect orders that visit both flowering and non-flowering branches of two distinct pawpaw cultivars (Sunflower and Susquehanna), along with their respective abundances. Ten trees from each pawpaw cultivar were selected to investigate the various pollinator types. In a completely randomized design, 40 wire cage traps with tangle trap adhesive were placed on both the flowering and non-flowering branches of each chosen cultivar. After 18 days of the flowering period, the traps were collected, and the insects captured were identified by order and counted. The data were analyzed using R software (R 4.3.2) and subjected to a one-way ANOVA with flower and non-flower of each cultivar, a two-way ANOVA, Least Significant Difference (LSD) means separation, with flowers and cultivars as the treatments. In 2023, ‘Sunflower’ had significantly more Dipterans and total insects (p-value: 0.3373 NS and 0.3740 NS). In comparison, ‘Susquehanna’ had significantly more Coleopterans (p-value: 0.40525 NS), and in ‘Susquehanna’, coleopterans had significantly more in the flower-branch (p-value: 0.0255*) for 2023. Additionally, data for 2024 will also be reported and will include additional data on insects observed inside the female receptive and matured male flowers from each cultivar.

In the warm growing season on the East Coast, broccoli crown development is often disrupted because insufficient cold accumulation for flower bud initiation and enlargement. As part of an effort to breed for adaptation to higher growing temperatures, we investigated whether the sensitivity is due to expression of one or more of the central genes involved in flower initiation. Broccoli transitions from vegetative to reproductive phase normally, it is the transition from reproductive meristem to floral meristem and flower bud that is arrested or delayed in warm temperatures. We compared the heat response of a highly sensitive genotype, ‘Clara’ and the most resistant available genotype ‘P13xP19’ (P. Griffiths, Cornell). Plants that had just entered the reproductive phase were exposed to temperatures that were either permissive (16/12°C Day/Night) or restrictive (28/22°C Day/Night) for three days, then RNA was isolated from the meristem. The RNA was sequenced, transcripts were identified and relative abundance of each transcript was determined. Transcripts were available corresponding to the genes of interest. The model is that various developmental and environmental cues affect expression of the integrator gene SOC. The expression level of SOC then influences a gene that maintains meristem (TFL1) and one that promotes flower development (LFY). The interplay between those genes in time and space is believed to control how big the meristem will get and when the meristem will start to make flowers. When LFY expression dominates, it promotes expression of AP1 (and paralogs) inducing floral primordia. A gene responsible for the heat sensitivity would have differential expression in heat only in the sensitive genotype. That was the case for TFL1 and one copy of SOC1, but not for the other genes. Therefore, heat sensitivity is caused by genes associated with meristem transition, not with the classic flower-initiation genes.

Water stress is one of the major limiting factors of crop growth and productivity worldwide. Plectranthus amboinicus (Jamaican Thyme) is an aromatic, spicy and medicinal plant which is also valued in the pharmacological industry. Although the plant is generally known to tolerate some levels of drought, its response to sequences of different water stresses is unknown. In this study, we investigated the effect of flooding and drought on the growth and development of Plectranthus amboinicus. The treatments were regular watering (RW), flooding (FL), drought (DR), and rehydration (RH) after drought. The result showed that plant height was significantly (p < 0.001) reduced in DR and FL plants while fresh aboveground weight was increased by ca. 17.4% in FL compared to RW. Stomatal conductance and transpiration rates were higher in FL plants but reduced drastically in DR. Moreover, chlorophyll fluorometric indices including maximum quantum yield efficiency of Photosystem II (Fv/Fm) and potential photosynthesis capacity (Fv/Fo) were significantly (p < 0.001) increased in the FL but decreased in DR plants. Leaf relative water content was significantly (p < 0.01) highest in the RH followed by the RW, and the least in DR and DH. Leaf cell electrolyte leakage was significantly (p < 0.05) higher in the RH followed by the RW while FL recorded the least cell electrolyte leakage. These results indicate that Jamaican thyme regulates physiological characteristics to tolerate flooding and demonstrate that DR poses a severe threat to plant development.

Phalaenopsis is the most popular potted plant worldwide. However, its long spikes often lead to increased shipping costs and risks. This study investigates the effectiveness of varying the concentration, timing, and frequency of paclobutrazol (PP333) applications on shortening the spike of Phalaenopsis Join Grace ‘TH288-4’. Also we examine on different progressive-raising temperature promoting inflorescence development for prior anthesis, and on spike-truncated treatment optimizing flowering performance. Three experimental groups were established based on different PP333 application schedules: T2, T2T3 and T7T8 group. The PP333 concentrations used were 0, 250, 500, 750, and 1000 mg·L-1, applied as foliar sprays. The shortest spikes, measured from base to first flower, were observed in the T2 group with 750 and 1000 mg·L-1; the T2T3 group treated with 500, 750, and 1000 mg·L-1 PP333; and the T7T8 group treated with 1000 mg·L-1. These treatments resulted in spike lengths of 16.7-22.2 cm, which are 54-69% shorter than the control ones. PP333 application had minimal effects on other traits except root diameter. Subsequently, four experimental groups: G20, G25, G30, and G35 group, were set up based on different final flower induction temperature. Mature plants were applied with 750 mg·L-1 PP333 by foliar spray, after four weeks moved to a cool room as 20/18℃. Until the flower stalk bore 0-3 nodes, the G25, G30 and G35 groups were transferred to 25/20℃. While the flower stalk bore 4-5 nodes, the G30 and G35 group were moved to 30/25℃. When the flower stalk bore 6-7 nodes, the G35 group was finally cultured under 35/30℃. Half of plants were randomly selected and truncated the spikes while the first flower bud was 1-1.5cm long. The spike of the G35 and G30 were truncated on the 21st week, which took only 113 and 117 days from the day started placing at a cool room. The G25 and G20 group took 124 and 138 days respectively. The days to flowering of G35 and G30 group were less than G20 at least by 45 days. However, the flower of G35 group performed unusual and were the smallest. All flowers of spike-truncated plants were bigger than the controls under different temperatures. This study establishes a PP333 treatment and a flower induction temperature protocol, offering a strategy to effectively produce single-flowered phalaenopsis.

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
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.

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.

Competition participants must bring your poster pdf on a thumb drive or the physical poster to your assigned room. You will be lined up to present to the judges in order of arrival. You will enter the room one at a time.

Students will be given 5 minutes to make a presentation to the judges, followed by a 2 minute period of questions and answers.

This competition is open to graduate students that have a poster presentation scheduled during the ASHS conference AND have also signed up to participate in this competition (Note: This is separate of the assigned time to present your abstract during the conference program).

Please note that if you do not also present your poster during the regularly scheduled Poster session, you will be disqualified from the Poster Competition.