Location: Subtropical Plant Pathology Research
2013 Annual Report
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.