695 Weed Control in Minor Crops After the Loss of Methyl Bromide

Abstract

The economics of pesticide production and registration has limited the number of pesticides registered for use in minor crops relative to agronomic crops. Current regulations such as the Food Quality Protection Act may further reduce the number of efficacious compounds registered for use on minor crops. Traditionally, the lack of registered pesticides for minor crops has been offset by soil fumigation. However, methyl bromide use is scheduled for phase-out in the United States by 2005, leaving a pest control vacuum in some crops. Loss of methyl bromide has stimulated research into the use of other soil fumigants for weed control. Methyl bromide, methyl iodide, propargyl bromide, 1,3-dichloropropene, and metham sodium have been tested alone and in combination with chloropicrin in laboratory experiments to determine their efficacy against Cyperus esculentus L (yellow nutsedge) tubers. All the fumigants controlled nutsedge equal to or better than methyl bromide and resulted in synergistic control when combined with chloropicrin. Although excellent weed control can be achieved with all the fumigants in the laboratory, weed control in the field with the same fumigant may result in poor or no control. Further research is necessary to optimize the field application of the remaining fumigants to maximize pest control. In the near future, to achieve the broad-spectrum pest control obtained with methyl bromide, growers will need to rely on multiple control strategies. The most promising replacement program for broad-spectrum pest control includes dichloropropene/chloropicrin fumigation followed by a herbicide program or mechanical weed control. To control problem weeds that are not controlled with the in-season herbicide program, a chemical fallow program should be instituted in the off-season to reduce weed pressure during the cropping season.