Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/26/2004
Publication Date: 3/31/2004
Citation: Nyczepir, A.P., Rodriguez-Kabana, R.R. 2004. Effectiveness of biofumigation for ring nematode control in a young peach orchard. 1st International Symposium Biofumigation: A possible alternative to methyl bromide. 1:64-65. Abstract. Interpretive Summary: Ring nematodes are widely distributed throughout the world with certain species considered to be economically important to the stone fruit industry. Probably the most studied ring nematode species on Prunus is Mesocriconema xenoplax. This ring nematode is the only plant-parasitic nematode that has been associated with the peach tree short life (PTSL) disease complex in the southeastern United States. Tree loss due to PTSL in South Carolina alone has been estimated at over $5 million per year. New preplant alternatives to chemical control (i.e., green manures-biofumigation) that are less hazardous to man and also more environmentally safe must be found to protect peach trees from this ring nematode. A grain sorghum that had been found to suppress ring nematode under greenhouse and field conditions was tested as a preplant biofumigant green manure under orchard conditions in the southeastern United States. As a biofumigant it was effective in suppressing the ring nematode population for up to 12 months, but was not effective as preplant fumigation with methyl bromide (23 months suppression). These data provide useful insights into the use of sorghum as a biofumigant and alternative to chemical control of the ring nematode on PTSL sites in the Southeast.
Technical Abstract: The experiment was initiated at the USDA, ARS Southeastern Fruit and Tree Nut Research Laboratory in Byron, Georgia in 1998. The site had a previous history of PTSL, but not of sorghum production. Plots consisted of five preplant treatments, as follows: i) sorghum as a green manure under plastic; ii) sorghum as a green manure w/o plastic; iii) preplant methyl bromide fumigation under plastic; iv) unfumigated soil under plastic; and v) unfumigated soil w/o plastic. In January 1999, all plots were planted to peach. Ring nematode populations did not differ among any of the treatment plots just prior to establishing the sorghum biofumigant and methyl bromide plots in September 1998. Four months (January 1999) after establishing the sorghum biofumigant and methyl bromide plots and prior to planting trees, ring nematode populations were greatest in the unfumigated soil than in sorghum + plastic, sorghum w/o plastic, and methyl bromide fumigated plots. In September 1999 (12 months after incorporating the sorghum as a green manure), no differences in nematode populations were detected among the unfumigated and two sorghum treatments plots. However, nematode populations were still suppressed in the methyl bromide plots. At 24 months after methyl bromide application (September 2000), the nematode population density in fumigated soil did not differ from the other treatment plots. Ring nematode populations continued to increase in subsequent sampling dates. Peach trees developed typical PTSL symptoms and died during this experiment. In 2001 and 2002, percentage of PTSL tree death was greater in unfumigated w/o plastic (29% and 54%) followed by sorghum + plastic (12% and 46%), sorghum w/o plastic (8% and 50%), unfumigated soil + plastic (4% and 29%), and methyl bromide (4% and 29%), respectively. No differences in trunk diameter were detected among any of the treatments. Sorghum as a green manure with and without plastic did suppress the population of M. xenoplax in the early stages of this experiment, but suppression did not last as long as preplant methyl bromide fumigation (i.e., 12 vs. 24 months, respectively).