Olive paper wasp

Taxonomic position: The olive paper wasp (Polistes olivaceus) belongs to the order Hymenoptera and the family Vespidae. As a social insect, it constructs nests made of paper-like material produced from chewed wood fibers. While they perform some ecological roles, in agricultural settings, they are considered significant pests due to their destructive feeding habits on high-value horticultural crops.

Host crops and damage: The species primarily targets ripening fruits and berries. Crops such as grapes, figs, peaches, and pome fruits are highly susceptible. The wasps use their strong mandibles to breach the skin of the fruit to feed on the sugary pulp. This behavior results in direct losses and creates secondary infestation points for fungi, bacteria, and vinegar flies, often leading to rapid fruit decay.

Biology and lifecycle: The colony cycle begins with an overwintered queen emerging in the spring to establish a nest. She produces the first generation of workers, which then assume the responsibilities of foraging and nest maintenance. The colony size grows throughout the season, peaking during late summer, which unfortunately coincides with the harvest period for many major fruit crops, leading to increased pressure on orchards.

Pest significance: The economic impact is twofold: direct yield loss and increased costs for harvesting labor due to the aggressive presence of wasps. Furthermore, their presence often complicates the manual harvest process, increasing the risk of stings to workers. In vineyards, their damage can lead to cluster rot, rendering the entire harvest unsellable for high-quality wine production.

Management strategies: Integrated pest management (IPM) is essential for controlling Polistes olivaceus:

• Installation of bait traps containing sugary solutions or fermented fruit juices to reduce worker populations.
• Systematic removal of nests located in the vicinity of agricultural fields during early spring.
• Rigorous sanitation practices, including the prompt removal of fallen or decaying fruit from the orchard floor.
• Usage of physical barriers, such as protective netting for fruit trees and vineyards.
• Careful application of insecticides, strictly following safety protocols and pre-harvest intervals to avoid residue contamination.