Adults and larvae of the plum curculio, Conotrachelus nenuphar (Herbst), damage the fruits of trees such as plum, peach, pear, apple, and quince. Adults are snout weevils about 1/4-inch long, brownish-black, with patches of gray, white, or orange colors and four prominent humps on the wings. Mature larvae are creamy-white, legless grubs with a brownish head.
The plum curculio overwinters in the adult stage in leaf and ground litter outside the orchard. When the adults emerge in the spring, they feed on and damage leaves, flowers, and newly set fruits of host trees. Feeding and egg laying on fruits lasts approximately six weeks and results in malformation, or catfacing, of the fruits that reach maturity and harvest. Larvae feed inside the fruits for two to three weeks and cause premature fruit drop. Mature larvae burrow out of the fallen fruits and enter the soil to pupate for approximately five weeks before emerging as adults.
This second generation, called summer adults, emerges during the late summer and feeds on fruits for a short period of time, leading to localized rotting. No egg laying occurs. Later, adults leave the field to overwinter in the surrounding areas. The best management practice by home gardeners to reduce infestations in backyard trees is to pick up all fallen fruits promptly (two to three times a week) before the larvae enter the soil. Put all fallen fruits inside a sealed plastic bag and place them in the trash. This practice, when done regularly, will reduce future problems. Contact your local Extension office for updated insecticide recommendations.
