Location: Subtropical Plant Pathology Research2010 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
Field trials were conducted to evaluate sunflower as a beneficial cover crop for vegetable growers currently relying upon soil fumigation for managing soilborne pests and as source of locally produced biodiesel. Field demonstration trials were conducted to facilitate adoption of soil solarization by vegetable and cut-flower growers as a nonchemical alternative to methyl bromide. Changes in soil microbial communities, populations of purple nutsedge populations and the soil density of root-knot nematodes were evaluated under continuous tomato monocultures or a sunn hemp cover crop and under various application rates of broiler litter and urban plant debris. On-farm trials were initiated to evaluate deep placement of steam for control of root knot nematodes and weeds in commercial flower production. Greenhouse and microplot trials were conducted to evaluate summer cover crops and weed species for nematode susceptibility. Non-fumigant, low risk pesticides were screened at multiple rates and timing of applications to determine efficacy for weed, disease, and nematode management
1. Novel application strategy to limit fumigant emissions. Atmospheric emissions and potential by-stander exposure risks are limiting grower adoption of alternative fumigants. A low disturbance soil fumigant applicator was designed to reduce dose rates and mitigate atmospheric emissions in broadcast, shanked applications. The apparatus was used in demonstration trials by commercial forest seedling nurseries in Georgia and Alabama and a commercial sod producer in Ft. Pierce, Florida. The apparatus was shown to reduce atmospheric emission of soil applied chemical fumigants
2. New chemicals for weed, nematode, and pathogen control. Crop protection materials are needed that provide broad-spectrum control of pests, but do not pose a risk to workers or the environment. ARS researchers at Fort Pierce, FL, in cooperation with University of Florida faculty conducted multiple field trials to evaluate a novel, reduced-risk compound for control of weeds, plant pathogenic fungi and bacteria, and plant parasitic nematodes. The compound’s broad-spectrum pest control activity at relatively low application rates was confirmed. Potential negative interactions with fertilizer applications were identified and remediated. A full patent has been filed and a licensee of the material has been identified.
3. Anaerobic soil disinfestation as an alternative to methyl bromide fumigation. Non-chemical alternatives to methyl bromide must provide effective control of pest complexes found in vegetable production systems. A cooperative research project between ARS researchers in Fort Pierce, FL, in cooperation with the University of California, Santa Cruz has resulted in the generation of new information on a technique that utilizes the combination of composted broiler litter and a carbon source with soil saturation and heating to create an anaerobic condition that induces weed, nematode, and soilborne plant pathogen control. When soil was amended with both litter and molasses, the effect on anaerobicity was stronger than that of either broiler litter or molasses alone. Control of yellow nutsedge emerging though the plastic early in the season in plots receiving the combination was equivalent to methyl bromide. The weed control observed during the bell pepper trial was maintained during the eggplant double crop. Second year field trials were completed and there was an indication of increased numbers of non-pathogenic, beneficial nematodes in some treatments. Root-knot nematode control was influenced by initial irrigation, molasses addition, and by the incorporation of composted broiler litter.
4. Management of Nematodes and other Soilborne Pests in Floriculture Production Systems. This Specific Cooperative Agreement between ARS researchers at Fort Pierce, FL and faculty at the University of Florida has yielded new information on susceptibility of a variety of important cut flower species to common species of root-knot nematodes in Florida. Experiments evaluating the susceptibility of selected flower cultivars to Meloidogyne incognita (race 2) and M. javanica revealed snapdragon and nasturtium were susceptible and supported high populations of both nematode species, while marigold, zinnia, salvia, and carnation cultivars evaluated were poor hosts. Delphinium showed light galling with some intermediate nematode population levels, but was significantly less susceptible than snapdragon and often similar to the resistant flower species. New data has also been generated on the use of soil solarization for nematode control in floriculture crops indicating that eggs and juveniles of Meloidogyne incognita can be killed over time at temperatures of 40-42oC, which are substantially lower than the temperatures of >45oC typically expected under solarization. However, lethal effects at reduced temperatures required exposure to those temperatures for >13 hours up to several days, so the recommendation to keep solarization films in place for 6 weeks remains unchanged.
5. The availability of registered chemical alternatives for the cut flower and bulb production industries is extremely limited. ARS researchers from Fort Pierce, FL have conducted replicated field trials and demonstration trials were with cut flower and caladium growers using multiple plastic tarp types and the alternative fumigants iodomethane:chloropicrin and dimethyl disulfide. Significant interactions were identified between cultivar selection, principally based on root knot nematode susceptibility, and fumigant selection. Repeated application of dimethyl disulfide resulted in a gradual increase in weed pressure. These crops have been included on the federal labels for the alternative fumigants.
Stanley, J.D., Burelle, N.K., Brito, J.A., Frank, J., Dickson, D.W. 2009. Biological Evaluation and comparison of four Florida isolates of Meloidogyne floridensis. Nematropica. 39:255-271.