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IPM Scouting in Stone Fruits

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Plum curculio - Conotrachelus nunuphar (Herbst)
IPM scouting in stone fruits > plum curculio
Plum curculio (PC) disperse from their overwintering sites to adjacent orchards in the spring when maximum temperatures are at least 75°F for 2-3 days or when mean daily temperatures are 55°-60°F for 3-6 days. Although PC may be in the orchard before fruit is present, this is not the appropriate time for control. Spring migration lasts about six weeks. Peak activity and the critical time for control usually occurs 2-3 weeks after shuck split as young fruit develops. Use of a PC degree day model, for tart cherry only, can delay insecticide treatment until 375 GDD base 50oF after full bloom. This GDD model should only be used with an intensive scouting program to ensure PC are properly monitored. Eggs laid prior to 375 GDD base 50F will produce larvae that develop and exit the fruit before tart cherry harvest. Oviposition stings after about 375 GDD base 50oF (after bloom) result in larvae in the fruit at harvest. The characteristic half-moon scar on fruit indicates an egg-laying event. PC is capable of causing high levels of injury in a short amount of time.
Mature larva Adult beetle Plum curculio scar
The mature larva is segmented and C-shaped, about 7 mm long, yellowish white with a brown head capsule, and legless. Below, the half-moon scar from PC egg laying. The adult beetle is about 5 mm long, dark brown with whitish to gray patches, and has four ridges on its wing covers, two of which are readily visible. Its long, downward-curved snout is about 1/4 to 1/3 its body length. Plum curculio scar
Monitoring: PC activity can be detected by visually inspecting fruit for signs of feeding or egg laying. Monitor most intensively from bloom through three weeks after shuck fall. Concentrate sampling on trees adjacent to hedgerow and woodlands, especially where damage has occurred. In addition, traps baited with pheromone and fruit volatile lures can be used to detect the presence of PC and to time sprays. Place at least 3 traps along orchard perimeters that are adjacent to PC overwintering habitats, such as woodlands. Traps will begin to capture PC as they move into the orchard and throughout the entire season.
View current Michigan growing degree day accumulations at Enviro-weather. Select a weather station from the map that is closest to your location. Then click on "fruit" for a list of weather resources and models for fruit production.
Additional information
This information was developed from A Pocket Guide for IPM Scouting in Stone Fruits by David Epstein, Larry J. Gut, Alan L. Jones and Kimberly Maxson-Stein. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2840).
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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Updated 7/24/07