Blueberry gall wasp

The blueberry gall wasp (Hemadas nubilipennis) is a small hymenopteran insect belonging to the family Pteromalidae. It is a specialized pest that specifically targets highbush blueberry plants to lay its eggs and complete its life cycle.

Adult wasps are very small and elusive, making them difficult to spot in an agricultural setting. Most identification efforts are focused on locating the physical structures created by the larvae on the host plant rather than observing the adults themselves.

The primary host plant for this species is the highbush blueberry (Vaccinium corymbosum). The wasp induces the formation of galls on terminal shoots, which disrupts the normal development of the stems.

By hijacking the plant's resources to create these structures, the wasp negatively impacts the bush's vigor. Severe infestations can lead to stunted growth and reduced fruit production, posing a challenge for commercial berry growers.

The most distinctive signs of infestation are the galls, often described as ink-berry shaped or kidney-shaped growths, appearing on the current season's growth.

These galls start as green, soft swellings that harden and turn reddish or brown as the season progresses. They contain internal chambers where larvae feed and mature.

During the dormant season, when the leaves have fallen, the galls remain attached to the branches, serving as an indicator of the previous season's infestation and a reservoir for future generations.

Manual removal of the infested shoots is the most effective and eco-friendly control strategy. Pruning the galls during the dormant period is critical to eliminate the larvae before they emerge in the spring.

Collected galls must be destroyed, preferably by burning or deep burial, to ensure the population is significantly reduced. Chemical intervention is rarely effective due to the protected nature of the larvae inside the galls, emphasizing the importance of rigorous sanitation practices.