Dispersal and diet of the Colorado potato beetle, Leptinotarsa decemlineata
The Colorado potato beetle (CPB) is a serious pest of potatoes and other solanaceous crops in North America and Europe. Reliance on chemical control has induced pesticide resistance, necessitating alternative management strategies based primarily on biological and cultural tactics. Better knowledge of this insect's movement, particularly its flight, could aid greatly in developing cultural controls.
Computer-linked flight mills were used to study flight of overwintered and summer-generation female CPB fed in the laboratory on seven different solanaceous plant species. Over 30 days, flight was greatest with starved overwintered females three to six days postemergence. Flight for the overwintered generation was negatively related to desirability of food, as measured by larval success. Flight for summer females, and fecundity for both generations, was positively related to food desirability. Starved females laid virtually no eggs; starved summer females did not fly. Flight and fecundity of individual females were not related within treatments.
Field investigations examined adult immigration to the same plant species over time and space, the distribution of overwintering adults, and disruption of their spring colonization to nonrotated potato crops. Recruitment to plots placed either near or far from potato crops showed that long-distance flight was primarily by starved overwintered adults, and also by fed first summer-generation adults. Two periods of short-distance dispersal occurred with older overwintered adults, and before diapause. Results suggest that the value of crop rotation depends on site-specific factors, not just the distance to overwintering sites or current-year potato crops.
Overwintering distribution was studied at three sites over two years. CPB concentrated within woody borders, averaging 60-200/m$\sp2$ in these areas before winter, compared to 8-13/m$\sp2$ within potato fields. Mortality was higher in fields than in borders, and greater near the ground surface. Only 15-44% of live beetles were in potato fields. In experiments with small plots, colonization of fields from woody borders was disrupted by a trap crop, either treated with pesticide or collected daily. Simulation models suggest that this colonization disruption tactic could significantly reduce pesticide applications and eliminate the need for disruptive treatments against adult beetles.