Paper wasp

Systematic position: Polistes diabolicus belongs to the order Hymenoptera, family Vespidae. As a social insect, it constructs exposed paper-like nests in protected areas such as tree branches, eaves, or under the foliage of garden plants, where it interacts with agricultural environments.

Affected crops: These wasps primarily target fleshy fruits and berries, including grapes, peaches, plums, pears, and raspberries. Their mandibles are adapted to pierce the skin of ripe fruits, allowing them to access the high-sugar content juices and pulp within.

Biology and life cycle: The colony cycle begins in early spring when a fertilized queen emerges from hibernation to establish a new nest. Over the summer, the population of worker wasps grows significantly. They are primarily responsible for foraging, which involves scouting for both protein (insects for larvae) and carbohydrates (ripe fruit juices for adults) in the vicinity of their nesting site.

Nature of damage: The damage caused is twofold. Firstly, direct consumption leads to substantial yield loss. Secondly, the holes created by wasps serve as entry points for fungal pathogens, such as Botrytis (gray mold) or various fruit rot bacteria, which can destroy the entire fruit crop if left unchecked. Furthermore, they can be a significant nuisance to orchard workers during harvesting.

Management and control: Protecting crops from Polistes diabolicus requires a multi-faceted approach:

• Installing bait traps with pheromones or sugary fermenting liquids to capture workers.
• Physically removing and destroying active nests during the night when the colony is dormant.
• Implementing netting or protective sleeves on fruit bunches like grapes to prevent access.
• Maintaining orchard hygiene by clearing fallen and overripe fruit promptly.
• Applying targeted insecticides only in cases of extreme infestation to protect the ecosystem.