Economic Impact of Insecticide Resistance in the Colorado Potato Beetle (Coleoptera: Chrysomelidae) on the Michigan Potato Industry

Abstract

Insecticide resistance in Colorado potato beetle, Leptinotarsa decemlineata (Say), in Michigan was first reported in 1984 but caused severe economic problems beginning in 1991. Surveys conducted by the Michigan Potato Industry Commission and Potato Growers of Michigan from 1991 through 1994 document the increased Colorado potato beetle control costs and yield losses resulting from insecticide resistance. In 1991 and after, statewide mean control costs were as high as $306/ha; costs for districts most seriously affected were as high as $412/ha. This is in contrast to $35-74/ha in the upper peninsula of Michigan, where resistance is not a problem. Yield losses were as high as 12.2% statewide and as high as 20.5% in seriously affected districts. Costs plus losses to the industry were $13.3 million in 1994 (13.7% of crop value). In response to these losses, nearly 100% of the crop was under some type of integrated pest management program. Scouting (96% of crop area) and crop rotation (78% of crop area) were the most common integrated pest management practices. The introduction of new insecticides may reduce or eliminate yield losses. However, costs of resistance will continue to accrue because relatively inexpensive insecticides are no longer effective and newly developed products are up to 5 times more costly. Long-term increased cost to the Michigan industry caused by insecticide resistance in Colorado potato beetle is estimated at $0.9 to $1.4 million/yr ($44 to $69/ha; $18 to 28/acre).