NC State Extension Publications

Description and Biology

Skip to Description and Biology

The oak shothole leafminer, Japanagromyza viridula, is a very small fly that emerges in early spring to feed on oak leaf buds and very young leaves. They feed by piercing the buds with their ovipositors (literally "egg placers") and lapping plant juice. As the buds break and new leaves expand, a tiny hole forms at the ovipostion injury site. The holes get bigger (up to 3/8 inch) as the leaves grow. Females eventually pierce leaves to lay eggs inside. Tiny maggots hatch and excavate blotch mines as they mature. Once mature, usually by the end of May, maggots leave their mines and drop to the soil where they pupate and spend the rest of the summer and the winter. Active mines are light green to tan but darken once they're abandoned. The damaged tissue eventually drops away leaving large, ragged holes. Female feeding holes and the leaf mines remain throughout the rest of the growing season. We have one generation per year in North Carolina.

Photo of symmetrical holes in a leaf

Oak shothole leafminers often leave symmetrical holes in new oak leaves.

Photo of leaf with oak shothole leafminer damage

Oak shothole leafminer damage can sometimes be quite spectacular.

Host Plants

Skip to Host Plants

Black oak, burr oak, Chinese chestnut, post oak, red oak, sand post oak, scrub oak, turkey oak, and white oak have all been reported as hosts of the oak shothole leafminer.

Photo of damage to red oak by oak shothole leafminer

Oak shothole leafminers infest most species of oaks in North Carolina.

Residential Recommendations

Skip to Residential Recommendations

Like most leafminers in this family, oak shothole leafminers have numerous parasites. Next year the infestation may not even be noticeable because of the parasites. Usually by the time the damage is noticed, the leafminers have already abandoned the mines. Applying a pesticide during the growing season will not help improve the appearance of an infested tree. It is probably better not to try to control these leaminers with pesticides.

Photo of oviposition damage by oak shothole leafminers

Oviposition damage by oak shothole leafminers persists long after the maggots have left the leaves.

Other Resources

Skip to Other Resources

For assistance with a specific problem, contact your local Cooperative Extension center.

This factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology & Plant Pathology

Publication date: July 7, 2020

N.C. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status.