Paper wasps

Paper wasps, belonging to the genus Polistes within the Vespidae family, are social insects that can become significant agricultural pests. While they are known as predators of caterpillars in some ecosystems, their tendency to feed on ripe fruit makes them a nuisance for orchardists and vineyard managers.

These wasps primarily damage high-sugar crops, including grapes, peaches, apricots, pears, and apples. By piercing the skin of the fruit, they access the pulp, which results in significant cosmetic damage and loss of market value for the harvested produce.

The biology of the paper wasp involves the establishment of colonies in paper-like nests. A queen overwinters and begins nest building in the spring. As the season progresses, the worker population grows rapidly, aligning with the ripening period of many fruits, which leads to increased pest pressure in the late summer and autumn.

Beyond direct feeding, Polistes species contribute to secondary damage by facilitating the entry of fungi and bacteria into fruits. Once a fruit is punctured, it is highly susceptible to gray mold (Botrytis) and other decay organisms, often leading to the rapid spoilage of neighboring fruits and cluster rot in grapes.

Effective management strategies against paper wasps include:

• Early-season removal of nests located on structures or near high-value crops.
• Installation of protective mesh bags on grape clusters to prevent physical access.
• Deployment of baited traps using sugar-based solutions to lure and capture foraging workers.
• Sanitation practices, such as the prompt removal and disposal of overripe or fallen fruit.
• Strategic timing of harvest to minimize the window of opportunity for wasp infestation.