Not known to transmit any human or animal pathogens.

Not known to vector any pathogens or other associated organisms.

Attaching lures to traps

IMPORTANT: Do not include lures for other target species in the trap when surveying for this target.

Note: Visual surveys for larvae are not an approved method and cannot be used to report negative data, but we are including some visual guidance to help surveyors who may observe larvae or signs of infestation. See Pascual, 1988 in the references and the Pest Datasheet for images. 

Signs of infestation include:

• Feeding damage: Thaumetopoea processionea larvae feed on oak leaves, where they cause visible damage on foliage and new buds. Feeding damage occurs from the oak bud-burst phase in spring until summer. Larvae strip each leaf to the mid-vein and lateral veins, which usually stay intact. Patches of stripped leaves are often seen among healthy leaves. Severe infestations and outbreaks can completely defoliate trees.
• Conspicuous larvae: Thaumetopoea processionea larvae are gregarious, living in groups on host trees. Groups of caterpillars are visible on branches, trunks, leaves or inside nests constructed from their silk. When moving, the caterpillars travel together in a distinct procession, with one or a few caterpillars in the lead and the rest following after them.
• Nests: Larvae build silken nests anywhere from 3-65 feet above the ground, on the trunk, branches, or partially buried between leaves and soil. The nests can be conspicuous and typically consist of a whitish silken mass attached to the host tree, often full of shed skins, frass, and caterpillars. Nests may remain on trees for up to a year following infestation and should not be touched as they are often full of the caterpillars' urticating hairs. 

The visibility of these signs on infested oak trees is dependent on how long the pest has been present. New infestations will have small nests, larvae will be difficult to spot, and defoliation will be limited. Conspicuous nests, aggregations, and significant or complete defoliation of host trees may occur within two to three years of establishment.

A Likelihood of Establishment Map is now available. This survey should only be considered in the states with appropriate conditions and suitable hosts for this moth. The map was produced by the SAFARIS Team. SAFARIS is a modeling framework that enables PPQ to quickly respond to emergencies, efficiently survey for pests, and assess potential pest impacts by collecting critical geospatial data and developing predictive models. SAFARIS is developed and maintained by the NC State University, Center for Integrated Pest Management (CIPM) with support from PPQ PERAL. The SAFARIS team used a likelihood of establishment model for oak processionary moth occurrence in the continental United States, that was developed by PPQ PERAL and NCSU CIPM, to support CAPS survey planning. The model predicts the suitability of an area for oak processionary moth occurrence based on the likelihood of favorable conditions for the insect occurring using tools and data within SAFARIS. The detailed method used in this assessment is described here.

Thaumetopoea processionea has a single generation per year and adults emerge from the end of July to mid-September in the United Kingdom. Traps should be placed when adults are expected to be present, from July to the end of September.

Trapping Survey

Deploy traps throughout the survey area. 

• Trap placement: 
  • Traps should be hung on oak branches 30-50 ft. above the ground. Depending on the height, surveyors may need to climb trees, use a mobile elevated work platform, or ladders/step-ladders to set traps.
  • Preferentially place traps on trees in open, sunny areas, at the border of forests or woodlands, or in isolated open places, which are preferred nesting sites for the pest.

Visual Survey

Note: Visual surveys are not an approved method and cannot be used to report negative data. We are including some visual guidance to help surveyors who may observe larvae or signs of infestation. 

• Surveyors may inspect oak trees while deploying traps. Focus efforts on trees where leaves have been stripped to the mid vein and check for the presence of nests or webs on the trunk or main branches. 
• Binoculars can help detect any pests in the tree canopy. 
• See the CAPS Pest Datasheet and Pascual, 1988 in the the references for images of tree infestation and different life stages of pests.

Warning: As the larvae contain irritating hairs, surveyors should wear appropriate personal protective equipment when handling any suspect caterpillars or nest material.

Survey for T. processionea where oak trees are present. Focus survey efforts on oak forests or areas with abundant oak trees.

Site inspection is optional, see Visual survey guidance above.

Gilligan et al. (2014) provides a screening aid for adult Thaumetopoea moths.

Some of the major literature sources for species identification include:

1. Groenen, F. 2010. Variation of Thaumetopoea processionea (Notodontidae: Thaumetopoeinae) in Europe and the Middle East. Entomologische Berichten 70(3):77-82.
2. Agenjo, R. 1941. Monografía de la familia Thaumetopoeidae (Lep.). Spanish Journal of Entomology 17(1-2):69-130.

Thaumetopoea processionea adults and larvae are easily mistaken for other species within the Notodontidae. The adults are distinguished morphologically based on species-specific wing patterns and the  shape of the head projection found between their antennae. This pest may be confused with Thaumetopoea pityocampa and T. pinivora, neither of which are currently present in the United States.

Other notodontids that are present in the United States and could be mistaken for T. processionea include Ceolodasyns unicornis, Heterocampa biundata, H. guttivitta, H. lunata, Ianassa lignicolor, Lochmaeus bilineata, Misogada unicolor, and Schizura ipomoeae; however, these are unlikely to be attracted to the T. processionea pheromone and are immediately distinguishable by having a proboscis.

The larvae of the oak processionary moth resemble those of fall webworm (Hyphantria cunea), eastern tent caterpillar (Malacosoma americanum), and forest tent caterpillar (M. disstria). These three species are native to the United States and can be found feeding on oak trees. Hyphantria cunea and Malacosoma disstria are distributed throughout the United States, and Malacosoma americanum is distributed throughout the eastern and central United States to the Rocky Mountains. Both native tent caterpillars and T. processionea are communal and construct nests in trees; however, nesting locations vary among species and only T. processionea constructs nests on the main trunk or branches.

The approved survey method is pheromone trapping using Thaumetopoea processionea lure (Z11Z13-16Ac [(Z, Z)-11,13- Hexadecadienyl acetate]. Commonly encountered non-targets attracted to this lure that are present in the United States include Amyelois transitella and Notodonta torva.

See the CAPS datasheet for images of adults, larvae, and silken nests of easily mistaken species.