Plum curculio

The genus Conotrachelus belongs to the family Curculionidae (weevils) within the order Coleoptera. These beetles are notorious for their significant economic impact on fruit production, with the plum curculio (Conotrachelus nenuphar) being the most destructive species, particularly in North America, where it poses a constant threat to pome and stone fruit orchards.

The damage caused by these insects is two-fold. Adults cause injury by feeding on buds, blossoms, and young fruit, leaving characteristic scars and punctures. However, the larval stage is the most damaging. Once hatched, the larvae bore into the fruit, feeding on the pulp and causing the fruit to become misshapen, decay, or drop prematurely, rendering the yield unmarketable.

The biology of Conotrachelus is closely tied to the host tree's phenology. After mating, the female cuts a crescent-shaped incision into the fruit skin, deposits an egg, and then cuts a flap of tissue to protect it. The larvae feed for several weeks, then exit the fallen fruit and burrow into the soil to pupate. The duration of this cycle depends heavily on temperature and moisture conditions.

A wide range of cultivated crops is vulnerable to infestation, including plums, peaches, nectarines, cherries, apples, and pears. In severe cases, failure to manage the pest leads to catastrophic crop losses, as the larvae render even the surviving fruit aesthetically unappealing and susceptible to secondary fungal infections like brown rot.

Management of the plum curculio requires a robust Integrated Pest Management (IPM) program:

• Strict sanitation by removing and destroying all infested dropped fruit immediately.
• Cultivating the soil beneath tree canopies to disrupt pupation sites.
• Utilizing barrier methods or trunk bands to intercept migrating adults.
• Applying targeted insecticides based on monitoring data and developmental stages.
• Monitoring adult activity using trap trees and pheromone-based lures to time control efforts accurately.