Location: Subtropical Plant Pathology Research2008 Annual Report
1a. Objectives (from AD-416)
Identify impact of pest management tactics on functional diversity of soil microflora and weed populations, their competitive interactions, and effects on crop health. Conceive, develop, and test tactics for the control of plant diseases, parasitic nematodes and weed pests of vegetable and floriculture crops. Research efforts will concentrate on the testing of novel chemical, biological, biorational, cultural, and organic pest conrol tactics and on improving their application technology. Identify combinations of pest control tactics that interact synergistically to improve pest control, are practical to implement, and will minimize environmental disruption. Research activities will focus on identifying combinations of pest control tactics that produce synergistic effects and minimize disruption to conventional crop production practices. Define the impacts of pest management and crop production practices on soil health including the suppression of soilborne pests.
1b. Approach (from AD-416)
A rational and sustainable approach to finding viable alternatives to methyl bromide is to utilize integrated pest management (IPM) programs where combinations of tactics are used to maintain economic damage from key pests below a tolerable threshold. Another approach is to redesign production systems minimizing the potential for outbreaks of soilborne pests. Availability of biologically-based pest management tactics must be increased for successful IPM programs for soilborne pests to be implemented. Growers must have the option of choosing tactics that fit the needs and constraints of their individual programs. Deployment of multiple or companion tactics is essential to alleviate selection pressure and manage potential increases in resistant pest populations. Synergistic effects from combinations of pest management tactics need to be determined. Specific research methodology will include combinations of cultural practices, biotechnology, biological, and conventional control methods.
3. Progress Report
Significant progress was made in determining the efficacy of chemicals nearing Environmental Protection Agency registration such as iodomethane:chloropicrin (50:50 Midas™) and dimethyl disulfide (Accolade™, 79:21) for control of weeds, root-knot nematodes (Meloidogyne spp.), and soilborne fungal and oomycete plant pathogens on floriculture crops including ornamental cockscomb (Celosia argentea var. cristata Kuntze), and sunflower (Helianthus annuus). Field trials were conducted on both research and commercial farms in southeastern Florida, and results have provided growers with important information on formulations, rates, and different plastics that provide acceptable control of important pests. Two patent applications were filed on novel, reduced-risk chemistries with pesticidal properties that could decrease the dependence on existing broad-spectrum fumigants. Laboratory, greenhouse, and field microplot trials were conducted and significant control of important weeds, nematodes, and fungal pathogens was associated with two compounds. Data on root-knot nematode/weed interactions were collected from microplot and field trials assessing both alternative fumigants and the new reduced risk chemistries for production of ornamental and vegetable crops including sunflower, tomato, cantaloupe, and bell pepper. Field trials were conducted to evaluate sunflower as a beneficial cover crop for vegetable growers currently relying upon soil fumigation for managing soilborne pests. Field experiments were implemented in March, 2008 to quantify the combined effects of fumigant application technology and methods and virtually impermeable films for reducing effective fumigant dosages. Microplot trials were established and treatment implemented to examine the effectives of organic amendments and cover crops on Meloidogyne spp. purple nutsedge, and Fusarium wilt of tomato. Addresses National Program 308 Methyl Bromide Alternatives, Component 1 Pre-plant Soil Fumigation Alternatives, Problem statement 1A Development of New Technologies for Alternatives and Integration into Commercial Crop Production Systems Currently Dependent upon Methyl Bromide Soil Fumigation and Problem statement 1B Pest Management Systems to Optimize Efficacy of Pesticides and Reduce Harmful Emissions.
1. *New chemicals for weed, nematode, and pathogen control Laboratory, greenhouse and microplot trials were conducted to evaluate novel, reduced-risk compounds for control of weeds, plant pathogenic fungi and bacteria, and plant parasitic nematodes. Two compounds were identified that have broad-spectrum pest control activity at very low application rates. The use of one of these materials has been expanded to include applications for the control of gastrointestinal parasites of small ruminants. Two invention disclosures have been filed and one provisional and one full patent have been filed on the inventions. This accomplishment addressed National Program 308 Methyl Bromide Alternatives, Component 1 Pre-plant Soil Fumigation Alternatives, Problem statement 1A Development of New Technologies for Alternatives and Integration into Commercial Crop Production Systems Currently Dependent upon Methyl Bromide Soil Fumigation.
2. Short-Term Methyl Bromide Alternatives for the Florida Floriculture Industry. This cooperative research project with the University of Florida has yielded new information on the use of soil solarization and fumigants including iodomethane (Midas™ iodomethane:chloropicrin, 50:50, 224 kg/ha) under metalized films as an alternative to methyl bromide for soil fumigation. Four field trials were performed under both commercial and experimental field conditions in three locations in Florida. Pest pressure varied according to location and ranged from high nematode and weed pressure, to low nematode but high weed pressure. Cut-flower crops evaluated were Celosia (Celosia argentea) and snapdragon (Antirrhinum majus). Results of studies show that Midas applied under metalized film provided weed control comparable to high rates of methyl bromide (98:2 400 lb/a) under high density polyethylene film, and lower rates of methyl bromide (98:2 200 lb/a) under metalized film. Low rates of methyl bromide (67:33 mbr:chloropicrin 200 lb/a) under metalized film did not provide good weed control. Soil solarization provided better control of white clover (Trifolium repens) than any fumigant tested. This accomplishment addressed National Program 308 Methyl Bromide Alternatives, Component 1 Pre-plant Soil Fumigation Alternatives, Problem statement 1B Pest Management Systems to Optimize Efficacy of Pesticides and Reduce Harmful Emissions.
3. Assessing soil microbial populations and activity following the use of polyglycerol polyricinoleate (PGPR)-based inoculants: effects on nematode suppression. This cooperative research project with Auburn University addressed the problem of developing methods for measuring soil microbial activity and population size in relation to the application of soil inoculants. Commercial biological inoculants were used to study changes in rhizosphere microbial activity and its relation to root-knot nematode suppression in field and greenhouse trials. Microbial activity was assessed using fluorescein diacetate hydrolysis, and population density by direct plate counts. Two inoculants, BioYield and FZB42, induced significant reductions in nematode eggs per gram of root, juvenile nematodes per ml, and galls per plant. Additionally, increases in total culturable bacteria and heat-tolerant bacteria in the tomato rhizosphere were detected in plants treated with BioYield and FZB42. Despite those changes in populations, no increases in microbial activity was detected using Food and Drug Administration hydrolysis, indicating that nematode suppression can result from PGPR-based inoculants and that these outcomes are related to bacterial density but not to soil microbial activity in the rhizosphere. This accomplishment addressed National Program 308 Methyl Bromide Alternatives, Component 1 Pre-plant Soil Fumigation Alternatives, Problem statement 1C Identification and Mitigation of Emerging Problems.
4. Nutsedge management can be enhanced through the combination of mulching and the biological control agent, Dactylaria higginsii. Multiple laboratory, greenhouse, and field trials have been conducted to evaluate the use of the biological control agent, Dactylaria higginsii, combined with multiple types of hay for solid substrate production of inoculum. For mass production of D. higginsii, 14 solid substrates in the form of dried, cut shoots of various plants were tested. These were tested alone or amended with 0.01% indole butyric acid (IBA), potato dextrose broth (PDB), or PDB + IBA. Conidial yields were highest when the fungus was grown on purple nutsedge hay without amendments for 4 weeks. Conidia produced on sorghum and cogongrass hays were slightly larger and thicker walled than those produced on other hay media. Conidia produced on sorghum were the most virulent on nutsedge seedlings. Cogongrass hay was most effective for suppression of nutsedge. This accomplishment addressed National Program 308 Methyl Bromide Alternatives, Component 1 Pre-plant Soil Fumigation Alternatives, Problem statement 1B Pest Management Systems to Optimize Efficacy of Pesticides and Reduce Harmful Emissions.
5. Significant Activities that Support Special Target Populations