Pinyon Pitch Mass Borer
Dioryctria ponderosae
A snout moth whose larvae bore under the bark of pinyon (and occasionally other) pines, producing the conspicuous globs of pinkish pitch on the trunk and large branches that give the pest its name. It is a serious pest of landscape pinyons, especially trees already stressed by drought or crowding.
🔎 How to spot it
The adult is a small grayish-brown snout moth, roughly half to three quarters of an inch long, with white zigzag markings on the forewings. The larvae are creamy white to pale pink caterpillars with a dark head, found tucked under the pitch mass. The clearest sign is the pitch itself: soft, popcorn-like masses of creamy pink pitch mixed with sawdusty frass oozing from the trunk and branch crotches.
🥀 Damage it causes
Larvae feed in the cambium and outer wood beneath the pitch mass, cutting large gouges that interrupt the flow of water and nutrients. Branches and trunk sections above heavy galleries weaken, lose vigor, and can break or die back. Repeated attacks over years disfigure and slowly decline a landscape pinyon, though a single small infestation rarely kills an otherwise healthy tree.
🛡️ Prevent it
Vigor is the best defense because the borer favors weakened, stressed trees: water pinyons deeply during drought but avoid overwatering, and thin overcrowded plantings, since both overwatering and crowding stress pinyons and invite attack. Avoid wounding the trunk and lower branches, and remove and destroy heavily infested, declining branches to lower local numbers.
🧯 If it is already here
For valuable trees, spray the trunk and major branches with a pyrethroid such as permethrin during the late-June-through-August adult flight to kill hatching larvae before they tunnel in; two or more treatments a season, repeated for at least two years, are usually needed. Established larvae are shielded under the pitch, so probing a tunnel with a flexible wire can kill some, but they often bore several inches and are hard to reach.
💡 Good to know
Most individuals take more than a year to complete development, and adults are active and lay eggs from late June through August. Pinyon is the main host, with ponderosa and other pines occasionally attacked. The creamy-pink pitch globs distinguish it from clear sap flow and from bark beetle pitch tubes, which are smaller and reddish.
🌱 Plants it attacks
4 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.