NC State Extension Publications

Description and Biology

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Pitch gall midges or resin gall midges are several species of tiny, mosquito-like, flies in the genus Cecidomyia that lay eggs on the twigs of pines in spring. Tiny maggots hatch and bore into the cambium layer of the twig, which cause pitch to ooze out and form a mass almost 1/2 inch wide. The maggots then develop inside the pitch -- hence the name resin gall midges or pitch gall midges. Fully grown maggots are slender, orange, and 3/16 to 3/8 inch long. They keep their rear spiracles in contact with air. Mature maggots either remain in the pitch masses to pupate or leave depending on the species. Those remaining in the pitch pupate in a silken cylinder. Pupae push through a thin cap to protrude from the pitch gall and adults soon emerge. Those maggots that leave the pitch gall pupate nearby. Pitch galls are most noticeable in early to mid April. Populations of pitch gall midges vary greatly from year to year. This is highly likely that the populations of other resin gall and pitch midges also fluctuate. We have one generation per year in North Carolina.

Pitch galls caused by midges in the genus Cecidomyia.

Pitch galls are usually white and up to almost 1/2 inch wide.

Photo by J.R. Baker, NC State University

A pitch gall caused by a midge in the genus Cecidomyia

After the midges leave, pitch galls sometime drip down from infested trees.

Photo by Lacy L. Hyche, Auburn University,

Host Plants

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Almost all species of yellow pines can be infested with pitch gall midges. White pine is infested by a single species, Cecidomyia candidipes, the only species of pitch gall midges that is confined to a single host in North Carolina. Pitch midge galls are relatively common on pines and they can cause minor dieback on loblolly pine. Sometimes pitch galls melt and drip down from infested pines onto cars unfortunately parked beneath.

Damage to a pine twig by a pitch gall midge.

Twigs often die from the pitch gall to the tip.

Photo by Whitney Cranshaw, Colorado State Univ.,

Residential Recommendations

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For best control, a pesticide would have to be directed at the adult stage if a specimen tree, important to the landscape, is small enough to spray. One way to figure out when to spray would be to put some of the pitch galls (with maggots) inside into a clear plastic bag and keep them in the shade outdoors. The maggots will pupate and the flies emerge inside the bag. When the tiny midges are seen crawling about inside the bag, that would be the time to spray with a contact insecticide. A systemic pesticide injected into the soil or trunk might give some control as well.


Professor Emeritus
Entomology & Plant Pathology

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Publication date: April 10, 2019
Revised: Feb. 19, 2024

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