Location: Subtropical Plant Pathology Research2013 Annual Report
1a. Objectives (from AD-416):
Expand on-going research to determine the most effective methods of applying anaerobic soil disinfestation (ASD) as an alternative to MeBr for control of key soilborne pathogens, plant pathogenic nematodes, and weeds. Impacts on crop yields, soil chemical and physical properties, and soil microbial communities will also be evaluated in raised bed and flat applications.
1b. Approach (from AD-416):
Multiple greenhouse, growth chamber, and field-scale trials will be conducted to determine if temperature plays a role in establishing the level of anaerobicity required to have an impact on weeds, nematodes, and plant pathogenic fungi; optimize tarp selection for maximum Eh and practicality; and evaluate summer cover crops as carbon sources for initiating treatments of ASD in a bell pepper-eggplant double crop. The ability to do ASD for production of crops that normally utilize flat fumigation, such as in-ground ornamentals, will also be determined in field trials. All trials will be replicated randomized complete block design in order to assess the impacts of all treatment combinations on multiple pests. The optimized system for ASD for flat and raised beds will be transferred to growers through field days and on-farm grower cooperator demonstration trials.
3. Progress Report:
This research is related to inhouse project objectives 1. Develop new management strategies for control of pests and pathogens currently or previously controlled by soil fumigants in vegetable and ornamental cropping systems; 2. Integrate cultural, biological, and chemical control tactics into technically feasible pest management programs for soilborne pests and pathogens; and 3. Identify impact of pest management tactics on biological and functional diversity of soil microflora, nematode, and weed populations, their competitive interactions, and effects on crop health and to develop genomic technologies to characterize changes in soil microbial populations in response to pest management tactics and the resulting effects on crop health. Anaerobic soil disinfestation (ASD) has been shown to be an effective strategy for controlling soilborne plant pathogens and plant parasitic nematodes in vegetable and other specialty crop production systems. Anaerobic soil disinfestation is based upon supplying labile carbon (C) to stimulate microbially-driven anaerobic soil conditions in moist soils covered with polyethylene mulch. To test the effectiveness of warm-season cover crops as C sources for ASD, a greenhouse study was conducted using a sandy field soil in which several warm-season legumes and grasses were grown and incorporated and compared to molasses-amended and no C source controls. ASD treatment utilizing cover crops as a C source resulted in soil anaerobicity values that were equal to the molasses-amended fallow control and greater than the no C source fallow control. Fusarium oxysporum (F.o.) survival was reduced by more than 97% in all C source treatments compared to the no C source control. Carbon source treatments were inconsistent in their effects on survival of Sclerotium rolfsii (S.r). In general, the number of M.i. extracted from tomato root tissue and root gall ratings were low in all treatments with cover crop C source, molasses C source, or composted poultry litter. Germination of yellow nutsedge tubers was highest in the no C source control, lowest in the molasses control, and intermediate from cover crop treatments. Warm-season cover crops have potential to serve as a C source for ASD in vegetable and other crop production systems, but more work is needed to improve consistency and further elucidate mechanisms of control of soilborne plant pathogens and weeds during ASD treatment utilizing cover crops. Two replicated field trials and two demonstration plots were established with commercial ornamental producers. The two replicated trials were conducted for flat field production of cut flowers and utilized the combination of molasses, composted broiler litter, water, and solarization plastic. ASD for cut flowers produced mixed results, which are highly dependent upon the level of cultivar tolerance to root-knot nematodes. ASD-treated plots produced the greatest number of marketable stems for two species. For the most nematode-susceptible crop, snapdragon, ASD and methyl bromide soil treatments produced the largest, most robust plants, but also the most severely galled root systems. In the large-scale caladium demonstration, ASD was conducted on raised beds with opaque film rather than with a solarization period. There was a one-day delay between the application of the amendments and soil saturation. Based on the grower yield data, ASD plots yielded approximately 50.5% of those treated with methyl bromide. In the second demonstration trial, a single plastic application was made in one lateral using clear solarization film and a white/black opaque film in the second lateral. The crop, Colocasia esculenta did poorly produced on clear plastic, but grew as well in the opaque film as in the adjacent fumigated block.