Pine Processionary Moth

The pine processionary moth (PPM), Thaumetopoea pityocampa, is not known to exist in the United States, but it may pose a serious threat to pine and cedar trees if introduced. The larvae of this high-consequence defoliator strip trees bare of foliage, making them vulnerable to other pests, diseases, and environmental stressors. These larvae may be seen at dusk, traveling in long nose-to-tail processions to feed in the canopy, and again at dawn when they return to their nests.


As they consume foliage, pine processionary moths cause damage far beyond tree decline. Severe infestations could dramatically alter ecosystems by reducing biodiversity, degrading critical habitat, and endangering threatened plants. Repeat defoliation can decrease timber yields and quality, impacting timber and forestry industries. If trade quarantines were enacted, these industries would be further impacted.

PPM larvae can also pose a health threat to people, pets and livestock. PPM larvae have tiny hairs on their bodies that cause severe skin irritation and respiratory reactions. Contact with larval hairs and nests has been associated with symptoms ranging from severe rashes to anaphylaxis. By causing such reactions in people and pets, a PPM infestation in the U.S. could also affect the outdoor recreation and tourism industries.


Global trade and travel provide the most common pathways for invasive pests, including PPM. Small, cryptic PPM eggs can be difficult to notice and could be transported unintentionally on host material intended for planting.

If introduced, this moth could spread unnoticed to new areas. PPM, as well as other invasive plant pests, can easily be transported to new areas on infested plants and firewood. Once introduced to a new area, the adults' strong alility to fly allows them to spread rapidly.


The moth’s main hosts are pines, but larvae have been known to feed on nearby cedar and larch trees when PPM populations are high. Despite their range of food sources, PPM are only known to complete their life cycle and produce adults on pine and cedar trees.


Although defoliation may draw your attention, pine processionary moth should be identified through direct evidence of the insect itself. Since PPM adults and larvae look similar to some native moths, seek confirmation from a diagnostician for identification.

The best way to recognize PPM is to watch for its processionary behavior on host plants. From late spring to summer larvae travel in unique nose-to-tail processions at dusk to feed and at dawn to return to their nests. Hundreds to thousands of larvae may be spotted making this daily commute on pines. Processionary behavior begins as the larvae mature, build nests on branches and trunks, and lighten in body color from brown to grey. Be careful and do NOT touch! PPM larvae grow noxious hairs that cause skin and respiratory irritation!

Monitor pines for conspicuous, white or orange-brown nests located on trunks or the undersides of branches. White silk nests may be the size of a tennis ball or larger and turn orange-brown over time, sometimes dislodging from the tree. If you find something that resembles an PPM nest, do NOT touch it! Nests are made of poisonous hairs just like the larvae.


Think you've spotted this pest?

If you think you've found this pest in your landscape contact your local extension office to see about sending in a sample.
Find your local extension office here.