Location: Citrus and Other Subtropical Products Research
2019 Annual Report
Objectives
1. Identify natural products and crop production systems that contribute to management of soilborne diseases, weeds, and nematodes.
1a. Develop combinations of commercially-available allylisothiocyanates (AITC) with organic amendments and other crop protection tools to improve weed, disease, and nematode control.
1b. Develop strategies to eliminate obstacles to the use of dimethyl disulfide.
2. Optimize application of anaerobic soil disinfestation (ASD) for application in vegetable and ornamental production.
2.a. Determine minimal input requirements and optimize organic amendments for effective application of ASD.
2.b. Increase environmental benefit of ASD through incorporation of reclaimed water.
3. Identify rootstocks for use with grafted vegetables with resistance or tolerance to pathogens and root-knot nematodes.
3a. Characterize rootstocks and associated microbiome for resistance or tolerance to soilborne pathogens of importance in the Southeastern U.S.
3b. Determine nutritional requirements and capacity of grafted plants to mitigate abiotic stress related to water quality.
Approach
The loss of methyl bromide for soil fumigation, limited registration of new chemical fumigants, and increased regulation of existing chemical fumigants has caused significant changes to crop production practices, including the registration and utilization of biofumigants and non-fumigant systems. Newly registered compounds, used alone or in combination, do not provide the same level of pest control resulting from the use of methyl bromide. Recognizing that some of the currently-registered chemical fumigants may, in the future, follow the same path as methyl bromide, the emphasis of the current research project will be to enhance the efficacy and understand the mechanisms of biologically and culturally-based management strategies for pathogens, weeds, and nematodes impacting vegetable and ornamental crops. Efficacy of management components will be examined individually and in combinations to achieve improved control of pathogens previously managed through soil fumigation using methyl bromide and to mitigate abiotic stress. Although some tactics have shown significant efficacy against individual pests or problems, integrated systems that address pest complexes are limited. It is critical that broad-spectrum pest control is achieved and approaches are compatible with the USDA, ARS mission to sustain a competitive agricultural economy by addressing pests that impact crop production as well as improving the health of the agro-ecosystem. Developed strategies will be built upon to gain a better understanding of pest biology, plant nutrition, pathogen and non-pathogen microbial interactions, and the impacts of pest control practices on the development of disease, weed, and nematode suppressive soil. Laboratory, greenhouse, and field experiments will be conducted independently, and in cooperation with ARS and University researchers, and through agreements with industry to broaden the scope of the research. Continued engagement with grower and industry partners will ensure effective transfer of technology which will include more efficient and environmentally compatible crop production systems that minimize health risks to workers and bystanders, and reduce inputs and environmental pollution from pesticides and fertilizers.
Progress Report
First year field trials for the evaluation of allylisothiocyanate (AITC) in cut flowers were established for multiple species. AITC was applied alone or in combination with herbicide active ingredients dithiopyr, oxyfluorfen with isoxaben, or a formulation containing trifluralin, isoxaben, and oxyfluorfen. Significantly fewer weeds emerged when AITC was applied with an herbicide partner. No phytotoxicity was observed in sunflower, however stunting and poor growth of snapdragon resulted from treatments that included the application of the formulation of trifluralin, isoxaben, and oxyfluorfen.
Three experiments were conducted using micro-chamber bioreactors for anaerobic soil disinfestation in which method of irrigation incorporation with organic amendments had a significant effect on the generation of volatile organic compounds and quantity of gases produced. Generated gases were characterized using gas chromatography. Amendment quantity had a significant impact on soil water retention. Soil samples for microbial community characterization were collected.
Two greenhouse trials were completed on the potential use of alternative carbon sources for generation of efficacious levels of cumulative anaerobicity during the anaerobic soil disinfestation (ASD) treatment period. Cover crops used as carbon inputs were found to have delayed carbon availability resulting in lower levels of anaerobicity than required for control of introduced pathogen inoculum. Additional potential carbon sources, including alga, lemna by-products, and biochar have been collected for carbon characterization.
First year greenhouse trials of tomato rootstock screening to determine susceptibility to Fusarium oxysporum f.sp. radici-lycopersici (crown rot pathogen), and F.o. f.sp. lycopersici races 1-3 (Fusarium wilt pathogen) were conducted and samples collected for quantification of pathogen infection using quantitative polymerase chain reaction (qPCR). Additional pepper rootstock and scion materials have been collected for extended screening for pathogen resistance. Preliminary results were used to identify multiple tomato rootstocks exhibiting resistance to race 3, which have not been previously reported.
Degraded water samples were collected from five water treatment plants, four water reclamation facilities, and two high saline on-farm irrigation sources. Differences in microbial communities characterized from these locations were highly influenced by collection time and temperature.
New protocols were developed for the characterization of agricultural soil metabolomes for soil treated using anaerobic soil disinfestation. Aqueous metabolites were characterized using 1D and 2D nuclear magnetic resonance coupled with metabolome database searches. Soil treated with ASD had metabolite profiles that were significantly altered compared to non-treated soil, with complex mixtures of uncharacterized compounds whose structures were indicative of anti-microbial compounds.
Small tank bioreactor systems were used to test various approaches to the removal of phosphorous and nitrogen from nursery run-off. One approach, utilizing the addition of iron to highly oxygenated water, resulted in the removal of more than 80% of phosphorous through the formation of iron-phosphate by filtration. A second approach, utilizing floating treatment wetlands composed of various aquatic plant assemblages, resulted in the removal of between 39-82% nitrogen and 26-65% phosphorous run-off.
Accomplishments
1. Adaptation of anaerobic soil disinfestation (ASD) for conventional commercial production systems. The loss of methyl bromide for soilborne pest control left few registered soil fumigants, which are not effective for the spectrum of pests previously controlled using methyl bromide. This leaves specialty crop growers needing broad-spectrum pest control at risk. ARS researchers in Fort Pierce, Florida, with cooperators engaged in an ARS-funded Areawide Project on ASD have conducted field trials with commercial producers on the efficacy of ASD using a combination of composted or pasteurized pelleted poultry manure and feedstock sugarcane molasses applied under totally-impermeable film for crop production without chemical soil fumigation. Use of ASD resulted in yields that were equivalent or higher than chemical fumigation and demonstrated breakeven prices, resulting in consistent positive returns for growers. Demonstration trials on commercial farms, conducted for multiple crops and seasons, resulted in adoption of ASD, particularly in buffer zone areas in which chemical fumigants cannot safely be applied. This approach provides specialty crop producers with an option for pest control for areas in which they currently have none. ASD requires slight modifications to the pre-plant practices currently employed, but provides economic, worker safety, and environmental benefits.
Review Publications
Paudel, B., Di Gioia, F., Zhao, X., Ozores-Hampton, M., Hong, J.C., Burelle, N.K., Pisani, C.N., Rosskopf, E.N. 2018. Evaluating anaerobic soil disinfestation and other biological soil management strategies for open-field tomato production in Florida. Renewable Agriculture and Food Systems. https://doi.org/10.1017/S1742170518000571.
Spangler, J.T., Sample, D.J., Fox, L.J., Albano, J.P., White, S.A. 2019. Assessing nitrogen and phosphorus removal potential of five plant species in floating treatment wetlands receiving simulated nursery runoff. Environmental Science and Pollution Research. 26:5751-5768. https://10.0007/s11356-018-3964-0.
Smith, C., Freeman, J., Burelle, N.K., Wechter, W.P. 2019. Screening cucurbit rootstocks for varietal resistance to Meloidogyne spp. and Rotylenchulus reniformis. HortScience. 54(1):125-128. https://doi.org/10.21273/HORTSCI13094-18.
Rosskopf, E.N., Abbasi, M., Aime, C. 2019. First report of guineagrass smut caused by Conidiosporomyces ayresii in North America. Plant Disease. PDIS-08.
D'Antuono, I., Di Gioia, F., Linsalata, V., Rosskopf, E.N., Cardinali, A. 2018. Impact on health of artichoke and cardoon bioactive compounds: content, bioaccessibility, bioavailability, and bioactivity. Book Chapter. Bentham Science Publishers, Sharjah, UAE, pp 373-443.
Ordonez Hinz, F., Albano, J.P., Wilson, P. 2019. Phosphate removal from nursery runoff waterusing an iron-based remediation system. Water. 11:795-805. DOI:https://10.3390/w11040795.
