Comparison of Traps for Monitoring Plum Curculio Adults (Coleoptera: Curculionidae) in Apple Orchards

Abstract

Effectiveness of four types of odor-baited or unbaited traps for monitoring overwintered adult plum curculios, Conotrachelus nenuphar (Herbst), on perimeter apple trees in Massachusetts orchards was compared. Black wooden pyramid traps placed on the ground next to apple tree trunks captured more adults than black plastic cylinder traps placed vertically on limbs within apple tree canopies, squares of clear Plexiglas placed vertically next to apple tree canopies to intercept incoming adults on the sticky-coated outward-facing surface, or “Circle” traps comprised of aluminum screen and fastened to limbs within apple tree canopies (which captured no adults). In no comparison did any of these traps baited with a combination of synthetic aggregation pheromone (grandisoic acid) and synthetic host volatiles (limonene and ethyl isovalerate) capture more adults than unbaited traps. None of the three types of baited or unbaited traps evaluated in commercial orchards (pyramid, cylinder or Circle) yielded captures of adults whose amounts or phenologies reflected amounts or phenologies of ovipositional injuries to fruit caused by plum curculio, although in unmanaged orchards amounts of capture by baited and unbaited pyramid and clear Plexiglas traps did reflect amounts of fruit injury. The only situation where odor bait enhanced trap effectiveness involved clear Plexiglas traps placed next to woods nearby an unmanaged orchard, where baited traps facing woods caught about 10× more immigrating overwintered adults than did unbaited traps. We conclude that odor-baited clear Plexiglas traps placed near woods can be useful for monitoring the beginning, peak and ending of overwintering adult immigration, but a more attractive blend of odor components is needed for effective monitoring by traps of any type placed near, beneath or within canopies of apple trees.