Technical Abstract: The plum curculio, Conotrachelus nenuphar (Herbst.), is a key pest of pome and stone fruit in eastern and central North America. For effective management of this insect pest in commercial apple orchards in the northeast, one of the greatest challenges has been to determine the need and timing of insecticide applications that will protect fruit from injury by adults. In a 2004-2005 study conducted in commercial apple orchards in seven northeastern states, the effectiveness of a reduced-risk IPM approach involving an odor-baited trap tree approach to determine need and timing of insecticide use against plum curculio based on appearance of fresh egg-laying scars was compared with existing management approaches based on three calendar-driven sprays or heath unit accumulation models that predict how long insecticide should be applied to orchard trees to prevent injury by plum curculio late in the season. Trap tree plots received a whole-plot insecticide spray by the time of petal fall, and succeeding sprays (if needed) were applied to peripheral-row trees only depending on a threshold of one fresh plum curculio egg-laying scar to out of 25 fruit sampled from a single trap tree. In both years, the level of plum curculio injury to fruit sampled from perimeter or interior-row trees in trap tree plots did not differ significantly from that recorded in plots subject to conventional management or in plots managed using the heat unit accumulation approach. Amount of insecticide used in trap tree plots was substantially less than that applied to plots managed with the conventional approach. Advantages and potential pitfalls of the trap tree approach to plum curculio monitoring in apple orchards are discussed.