Metallic pitch blister moth

French common name: Nodulier métallique
Scientific name: Petrova metallica (Busck)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Tortricidae
Partial list of synonyms:
- Petrova metallica (Busck)

Distribution

Quebec, British Columbia

The metallic pitch blister moth is distributed widely in western North America, from Minnesota, Colorado, and California in the south, northward throughout British Columbia and western Alberta to southern Yukon, and in the Cypress Hills of southwestern Saskatchewan. Petrova metallica seems to occur at higher elevations at least 800 m above sea level.

Damage, symptoms and biology

Tree injury results from larval feeding. Young larvae ofP. metallica begin feeding on current-year shoots of branches and sometimes on leaders. Each larva excavates only one feeding site and covers it with a resinous blister during its developmental period: it mines lengthwise within the twig or stem, frequently killing or injuring buds and some first-year cones. Injury may result in dead terminals, crooked or multiple leaders, height reduction, and a less effective crown form on shelterbelt trees.

This species attacks young to mature trees, but most reported injury has occurred on 0.5- to 5.0-m-tall pine trees growing in natural stands, plantations, seed orchards, nurseries, and on planted shelterbelt and ornamental trees.

Adults of the metallic pitch blister moth are small, mottled, metallic gray moths with a wingspan of 14–21 mm. They appear in the field during June and July. The life cycle of the metallic pitch blister moth, although less understood, appears to be 2 years in its northern range in Alberta and Saskatchewan and 1 year in its southern range. Moths of this species are also present each year.

Other information

Plantations of a single species of host pine tree commonly support high population levels. A similar relationship between tree size and P. metallica attacks was observed in a ponderosa pine plantation.

Natural control agents of the two Petrova species include several insect parasitoids, some of which are common to both hosts. The combined effects of all known parasitoid species usually cause less than 10% mortality of larvae and pupae. Predation of Petrova larvae by insect predators while the larvae are exposed during migration on branches may be important, but this has not been investigated. Birds such as chickadees may also contribute as natural control agents by preying on larvae, pupae, and adults. Weather may also be a factor: hail may be detrimental to larvae, while wind or cool rainy conditions may affect moth flight and egg laying.