Paper wasp

Systematic position: The paper wasp (Polistes gallicus) belongs to the order Hymenoptera and the family Vespidae. They are social insects known for constructing aerial nests made of a paper-like substance created from chewed plant fibers and saliva.

Crops affected: This species is considered a significant pest for commercial vineyards, orchards, and berry plantations. They show a strong preference for high-sugar crops, particularly grapes, peaches, plums, figs, and late-season pears, posing a risk to the commercial value of these harvests.

Biology and life cycle: The annual cycle begins when overwintered queens emerge in the spring to establish new colonies. As the season progresses, the colony expands rapidly. By late summer, when fruit sugar content peaks, the population of worker wasps is at its highest, leading to intense foraging pressure on nearby crops.

Nature of damage and harmfulness: The wasps damage the outer layer of the fruit, allowing them to extract juices and flesh. The economic damage is compounded by the fact that wasps introduce pathogens into the fruit, leading to rapid decay and the spread of various fungal and bacterial rots, which often makes entire bunches of grapes unmarketable.

Control measures: Integrated pest management strategies are essential for reducing wasp pressure. Key techniques include:

• Installing attractant traps containing sugar solutions or fermented baits;
• Locating and removing nests early in the spring before the population peaks;
• Using protective fine-mesh bags for valuable clusters of grapes;
• Sanitation practices, such as immediate removal of fallen or damaged fruit to reduce food availability.