Pine Processionary Moth

This organism is not known to be present in the United States but poses a threat. The pine processionary moth (PPM), Thaumetopoea pityocampa, is not known to exist in the United States, but if introduced, it may pose a serious threat to pine and cedar trees (Cedrus spp.*). The larvae of this high-consequence defoliator strip trees bare of foliage, leaving them vulnerable to other pests, diseases, and environmental stressors.


As they consume foliage and harm individual trees, pine processionary moths can also pose environmental, economic, and health threats. 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 experience further strain.

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 plant parts. Once introduced to a new area, the adults' strong alility to fly allows them to spread rapidly.


The moth’s main hosts are pines (Pinus spp.), but larvae have been known to feed on nearby cedar (Cedrus spp.*) and larch (Larix spp.) 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.

*The common name "cedar" refers to two distinct genuses, Cedrus and Thuja. Cedrus spp. are not native to the Americas. It is unknown whether Thuja spp. could be affected by PPM.



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 lepidopterist for identification.

The best way to recognize PPM—or any Thaumetopoea spp.—is to watch for its processionary behavior on host plants. When food in a host tree becomes scarce due to defoliation, large groups of larvae will travel in head-to-tail processions in search of a new host. These processions are again formed as the larvae travel from branches down to the soil, where they will pupate. Hundreds to thousands of larvae may be spotted traveling together in this manner. 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 among branches. White silk nests may be the size of a tennis ball or larger and turn orange-brown over time. If you find something that resembles a 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.