Blueberry gall midge injury more common this year

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

The blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae), is a pest of blueberries across the United States and Canada. This season, we have seen higher levels of damage from this pest than in recent seasons. Midge larvae have been reported to damage fruit buds and they can also injure vegetative growth. The vegetative growth seems to be the most commonly-injured tissues seen this year in Michigan fields, and this is most easily seen in the form of side branching by stems where the growing tip was killed back in late May and June. Distorted and blackened shoot tips are also a distinctive feature of the damage caused by gall midge.

Adult flies of the blueberry gall midge overwinter in the soil and emerge in spring to mate and lay eggs. They are fragile and approximately two to three millimeters long. Mature larvae are about one millimeters long and 0.3 millimeters wide, legless, and yellow to red in color. The biology of the blueberry midge is poorly known in Michigan, but from the timing of initial damage, emergence seems to start in May which coincides with bloom in many fields. Adults are short-lived and probably last only from one to a few days. Under Michigan conditions, we expect more than one generation through the summer, making control of this pest challenging.

Information for this article was gathered from observations in Michigan and from the University of Florida fact sheet, EENY-136. All photographs were taken in Michigan blueberry fields.

Gall midge larvae
Gall midge larvae (small white specks) exposed
after opening a damaged shoot tip.

Shoot tips killed by gall midge feeding
Shoot tips killed by gall midge feeding cause side
branching of stems.

Typical blackened tip of a vegetative shoot infested by gall midge
Typical blackened tip of a vegetative shoot
infested by gall midge. Note the characteristic
curled young leaves.

Dr. Isaacs's work is funded in part by MSU's AgBioResearch.

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