Plum curculio

The plum curculio (Conotrachelus nenuphar) is a significant pest belonging to the order Coleoptera and the family Curculionidae. It is considered one of the most damaging insects in North American orchards, particularly affecting stone fruits, and remains a constant challenge for professional fruit growers worldwide.

This pest primarily attacks stone fruits, including plums, peaches, nectarines, cherries, and apricots, as well as pome fruits like apples and pears. The presence of the beetle can lead to total crop loss if left unmanaged, as the larvae feed directly within the fruit, rendering it unsalable and unsuitable for processing.

The biological cycle of the plum curculio consists of egg, larval, pupal, and adult stages. The adult beetles overwinter in leaf litter or soil and emerge in the spring. A distinguishing behavior is the female's method of egg-laying: she makes a crescent-shaped incision in the fruit, placing an egg within the flap of skin to ensure protection for the developing larva.

Damage is twofold: the adults feed on the fruit surface, causing scarring and deformity, while the larvae burrow into the fruit, feeding near the pit. This activity causes the fruit to drop prematurely and often leads to secondary rot caused by fungal infections that enter through the feeding and egg-laying sites.

Management strategies focus on reducing the beetle population through integrated pest management (IPM) practices. Key methods include:

• Prompt removal and destruction of dropped fruit to kill larvae before they exit into the soil.
• Application of appropriate insecticides at the petal fall stage and subsequent intervals.
• Cultivation of the soil under the tree canopy to disrupt the pupation process.
• Monitoring adult activity using specialized traps to time chemical interventions correctly.