Timing of Infestation by the Colorado Potato Beetle (Coleoptera: Chrysomelidae) on the Suppressive Effect of Field Released Stinkbugs (Hemiptera: Pentatomidae) in Washington

Abstract

Delaying infestation of potatoes by overwintering Colorado potato beetles Leptinotarsa decemlineata (Say) by either 10 or 20 d following plant emergence increased damage to the potatoes. The egg deposition period was reduced from 5 to 3 wk; both increased rates of egg deposition and feeding occurred over a shorter period of time. Potatoes infested at plant emergence by Colorado potato beetle had fourth instars feeding during a 4-wk period of time while infestation 20 d after plant emergence reduced this feeding period to 2 wk and resulted in significantly greater defoliation than those infested at plant emergence. Delayed infestation by either 10 or 20 d had a negative effect on predation by Perillus bioculatus (Fabr.). Potato plants infested by Colorado potato beetles at plant emergence with releases of P. bioculatus 4 d later had the greatest percentage reduction in fourth instars and provided significantly greater foliage protection than plants infested at 10 or 20 d after plant emergence. Based on population levels of fourth instar Colorado potato beetles, multiple releases of P. bioculatus and P. maculiventris were not significantly more effective than a single release based on population comparisons of beetles. However, three releases (three predators per plant each release) of both species of predators provided greater potato foliage protection than a single release (three predators per plant).