Location: Citrus and Other Subtropical Products Research
2024 Annual Report
Objectives
1. Develop and improve non-fumigant crop production approaches to maximize efficacy and optimize crop productivity.
1a. Optimize anaerobic soil disinfestation (ASD) application for effectively managing soilborne pests and increasing plant health and yield.
1b. Combine ASD with novel crop production tools for increased value.
1c. Develop and implement adaptation of methyl bromide alternatives to soil fumigation, including non-fumigant approaches to management of nematodes and other pathogens in California carrot and strawberry production, such as anaerobic soil disinfestation.
2. Establish methods for improving soil health, plant nutrition, and pathogen management in greenhouse and other controlled environment production systems.
2a. Increase the environmental benefit of ASD through incorporation of reclaimed water for nursery production.
2b. Utilizing ASD to managing bacterial wilt in controlled environments.
2c. Ascertain methods to increase microgreen production and manage pathogens.
3. Characterize microbial communities and plant interactions that contribute to soil health and plant disease management.
3a. Identify abiotic and biotic factors that contribute to rootstock resistance breakdown.
3b. Characterize the relationship between the soil microbiome and plant health.
Approach
Soilborne plant pathogens, weeds, nematodes, and nutrient mismanagement cause considerable yield losses in vegetable and ornamental crops. In the Southeast, although methyl bromide was banned, soil fumigation remains a critical component in vegetables and fruits production. Alternative chemicals continue to be investigated, but only 1,3-dichloropropene, chloropicrin, an allyisothiocyanate biofumigant, and methyl isothiocyanate generators remain available. Dimethyl disulfide is registered, although there is currently no U.S. distributor. These materials, applied alone or in various combinations, do not provide the spectrum or level of control that resulted from the use of methyl bromide. Dependence on fumigation leaves growers vulnerable to regulatory and economic forces associated with pesticide use. Crop production systems, soil treatments, and nutrient management tools that control pests and maximize yield, while reducing negative environmental and human impacts, are the focus of the proposed research project on development and improvement of biological and cultural management strategies for pathogens and weeds impacting fruit, vegetable, and ornamental crop yields. These systems will be assessed holistically for their potential impact on the environment and product quality. An integrated approach of improving and understanding the role of the soil microbiome, soil quality, and plant nutrition in mitigating impacts of biotic and abiotic stressors will result in regenerative agricultural practices that increase crop productivity. While independent research will be conducted in laboratories, greenhouses, and in the field, ongoing and new collaborations with other ARS, university, and industry researchers will broaden the scope of the research. Continued stakeholder engagement is critical for effective technology transfer and for ensuring practical tool delivery. Mitigating the impact of soilborne pests impacting crop production while improving U.S. agroecology aligns with the USDA-ARS mission, “to sustain a competitive agricultural economy".
Progress Report
To provide growers with additional tools to manage soilborne pathogens, weeds and, plant-parasitic nematodes, ARS scientists at Fort Pierce, Florida, have conducted experiments to improve anaerobic soil disinfestation (ASD), a regenerative agriculture preplant technique, the focus of Objective 1. ARS scientists partnered with strawberry growers, industry representatives, and University of Florida researchers to conduct field experiments throughout Florida to establish the best carbon:nitrogen ratio for strawberry pest control and yield. Additional trials were conducted to determine if control of Macrophomina was improved by utilizing clear UV film alone (solarization) or with ASD. Fulfilling Sub-objectives 1a and 1b, field trials were repeated with treatments in the same locations as in the previous year to characterize long term effects on the microbial. Greater yields were observed when ASD was used for production of winter melon, but not jicama, but soil treatments influenced post-harvest characteristics. Additionally, carrot accessions with various reported levels of resistance to root-knot nematodes (RKN) were exposed to three different species or a mixture of RKN species. In collaboration with University of California researchers, first year field experiments on ASD for management of RKN in carrot were completed and have been established for the second year. Additionally, proof-of-concept experiments were conducted to establish greater soil mobility of nematicides using inactivated virus nanoparticle encapsulation. Encapsulated nematicides were found to provide better RKN control than nematicides directly applied to soil.
To increase ASD adoption for both conventional and organic growers, innovative tools have been coupled with ASD, which is the focus of 1b. To better manage nutsedge, ASD was combined with multiple herbicides and second year trials have been established utilizing different application approaches. Biodegradable and silage mulches were also tested for use in ASD to improve sustainability of the method. Use of silage mulch resulted in high levels of anaerobicity and provided weed and RKN control for organic carrots grown in high tunnels. A greenhouse experiment was conducted to test different types of biomulch plastic, polylactic acid (PLA) and polyvinyl alcohol (PVA to determine if thickness and biomulch composition influence ASD efficacy.
Under objective 2, greenhouse experiments were conducted to test the potential utility of utilizing reclaimed water for ASD prior to field or large-scale application. Initial characterization of four reclaimed water samples identified potential safety concerns of widespread utilization, as it was discovered that water treatment facilities test only for coliform bacteria and not for heavy metals, pharmaceuticals, nor toxins. Fulfilling Sub-objective 2b, two cultivars of blueberry plants were planted in ASD treated soil and pine bark mulch and were inoculated with either Ralstonia solanacearum before the ASD application or after transplanting into untreated substrate. Experiments on the impacts of multiple LED light spectra on microgreen productivity and nutritional composition were repeated in accordance with Sub-objective 2c.
The focus of Objective 3 is to identify the factors that contribute to resistance to plant pathogens and phytopathogenic nematodes. To understand the breakdown of RKN resistance in resistant tomato cultivars, experiments were repeated in which tomatoes were grown under varying temperature regimes using different types of soil were challenged with multiple RKN species or a combination (3a). Under sub-objective 3b field soil was collected and exposed to various conditions to achieve soil sterilization or pasteurization to characterize the activity of the microbial community that is required for successful application of ASD.
Accomplishments
1. Ralstonia solanacearum, a soilborne bacterium, is impacting Florida blueberry production. An ARS scientist from Fort Pierce, Florida has met with blueberry growers throughout the state and has isolated this bacterium from plants, soil, and irrigation water. Genetic characterization of the field isolate has established that at least two different genetic lineages, which could have differing host ranges, are infecting blueberry. Growers prefer the cultivar ‘Arcadia’ because it typically fruits when the market is high, however, this cultivar appears to be the most susceptible to R. solanacearum, with a few growers observing up to 90% loss of these bushes. Identification of the strains of the bacteria will allow more precise screening of plant material and soil treatments.
Review Publications
Bai, J., Rosskopf, E.N., Jeffries, K.A., Zhao, W., Plotto, A. 2023. Soil amendment and storage effect the quality of winter melons (benincasa hispida (thunb) cogn.) and their juice. Foods. 12(1): 209. https://doi.org/10.3390/foods12010209.
Vincent, I., Rosskopf, E.N., Brecht, J., Dufault, N., Sandoya-Miranda, G., Zhao, X. Comparing the performance of lettuce genotypes in high tunnel organic production systems using anaerobic soil disinfestation. Agronomy Journal. 2024. 14(4):764. https://doi.org/10.3390/agronomy14040764.
Opdensteinen, P., Charudattan, R., Hong, J.C., Rosskopf, E.N., Steinmetz, N. 2024. Biochemical and nanotechnological approaches to combat phytoparasitic nematodes. Plant Biotechnology Journal. 1-17. https://doi.org/10.1111/pbi.14359.
Rosskopf, E.N., Di Gioia, F., Vincent, I., Hong, J.C., Zhao, X. 2024. Impact of the ban on the soil-applied fumigant methyl bromide. Phytopathology. 114(6): 1161-1175. https://doi.org/10.1094/PHYTO-09-23-0345-IA.