Location: Subtropical Plant Pathology Research2012 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 related to inhouse project objective 4. Define the impacts of pest management and crop production practices on soil health including the suppression of soilborne pests. Anaerobic soil disinfestation 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 to stimulate microbially-driven anaerobic soil conditions in moist soils covered with polyethylene mulch. To test the effectiveness of warm-season cover crops as carbon sources for anaerobic soil disinfestation, 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 carbon source controls. Greenhouse pots were irrigated to fill soil porosity and covered with a transparent polyethylene mulch to initiate a 3-week anaerobic soil disinfestation treatment prior to planting tomatoes. Soilborne plant pathogen inoculum packets, yellow nutsedge tubers, and Southern root-knot nematode eggs and juveniles were introduced at cover crop incorporation. Anaerobic soil disinfestation treatment utilizing cover crops as a carbon source resulted in soil anaerobicity values that were equal to the molasses-amended fallow control and greater than the no carbon source fallow control. Propagules of the fungal plant pathogen Fusarium oxysporum survival was reduced by more than 97% in all carbon source treatments compared to the no carbon source control. Carbon source treatments were inconsistent in their effects on survival of Sclerotium rolfsii and control increased with grasses used as carbon sources. In general, the number of root-knot nematodes extracted from tomato root tissue and root gall ratings were low in all treatments with cover crop carbon source, molasses carbon source, or composted poultry litter. Germination of yellow nutsedge tubers was highest in the no carbon source control, lowest in the molasses control, and intermediate from cover crop treatments. Warm-season cover crops have potential to serve as a carbon source for anaerobic soil disinfestation 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 anaerobic soil disinfestation treatment utilizing cover crops. Two field trials were conducted to determine the impact of using opaque polyethylene film rather than clear film during the three-week disinfestation period. The first field was discontinued after treatment application due to a significant delay in plastic application resulting from significant rain events. In the second trial the level of anaerobicity was increased with the use of virtually impermeable films and totally impermeable film in one trial, but not in both trials. The highest yields of cucumber fruits were also harvested from plots covered with these films during treatment. Significantly more purple nutsedge emerged from the plot treated using the standard high density polyethylene than from any other plastic type.