Wasps Eating Blueberry Blossoms

Description

• Hemadas nubilipennis is a small, shiny black chalcid wasp. They have light amber legs and antennae. Larvae are legless and creamy white. Larvae are not commonly seen, as they live and feed with the gall created by the female.

Life Cycle

• Adults emerge from galls in mid May through June around the time buds break. Females crawl around the plant in search of a developing shoot. Once they've found the right spot they lay several eggs within the stem. They then stab the tip of the stem causing serious damage. The damage results in abnormal bud growth around the eggs called a gall. Within 12 to 14 days the eggs hatch and begin feeding on the walls of the gall. As they feed, more abnormal plant tissue is created and the gall grows in size. By August the gall stops growing, the lava pupate and overwinter in the gall until spring when they emerge as adults.

Damage

• Wasps may not eat the blossoms off a blueberry plant but they can prevent it from blooming and forming berries. The damage caused by the female as she stabs the developing stem prevents buds from forming or blooming on that stem. In addition, valuable nutrients are sapped from the plant as it forms galls to feed the wasp larvae.

Control

• There are currently no tested chemical controls for these parasitic wasps. The Wild Blueberry Network Information Centre of Nova Scotia notes that natural control in the form of predation and parasitism may take care of around 50 percent of galls. Pruning galls from your blueberries as soon as they form is a the most reliable control method.