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.
