Reduction of insecticide activity by carbon residue produced by burning grass seed fields after harvest
1990
Kamm, J.A. | Montgomery, M.L.
Annual burning of straw and stubble harvest on commercial grass seed fields produces carbon residue that is incorporated into the surface layer of soil by winter rains. When intact cores of this layer were removed and treated with chlorpyrifos in the laboratory, the mortality of house crickets, Acheta domesticus (L.), caged on treated cores from fields burned three consecutive years was 95% and from fields burned 16 consecutive years was 15%. Chemical analysis of treated cores with and without carbon residue indicated similar amounts of chlorpyrifos. Reduced mortality is caused by the strong adsorption of the toxicant by carbon residue that resulted from held burning. Efficacy of diazinon, fonofos, dimethoate, and fenvalerate was also reduced significantly by the carbon residue. In grass seed fields, we suggest that mechanical methods of straw removal, either alone or in combination with alternate year burning, be used to eliminate or slow the rate of accumulation of carbon residue that interferes with activity of insecticides.
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