NC State Extension Publications

Description and Biology

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Pine tortoise scale insects, Toumeyella parvicornis, are relatively large soft scales that feed on the newer growth of pines. They are rarely found on larger limbs. Mature females grow to be hemispherical and resemble the shells of miniature tortoises. Pine tortoise scales spend the winter as developing females on pine twigs. Overwintering females are reddish brown and slightly wrinkled. Females resume growth in the spring and mature in April and May. Up to 500 eggs are laid beneath the female's body. Tiny, amber-colored crawlers emerge in late May and June. Crawlers move away from the parent, settle on a twig, and begin forming a white crystalline substance on their bodies. After some weeks, male emerge to mate with new females. Male pine tortoise scales are tiny winged insects that die after mating. Females develop into ¼ inch somewhat flat scales that overwinter on the bark of new growth.

Pine tortoise scale insects

Pine tortoise scale insects frequently cluster on pine twigs.

Pine tortoise scale insect crawlers

Pine tortoise scale insect crawlers begin emerging in late May.

Host Plants

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Scots pine and jack pine are the two species most severely attacked by pine tortoise scales in Christmas tree plantations in the northern United States, but red and Austrian pines are also affected there. Apparently most pines can be infested including Virginia pine, Swiss mountain pine, loblolly pine, shortleaf pine, slash pine, Caribbean pine, and Chinese pine. Infested branches often become dark with sooty molds that grow in honeydew excreted by the scales. Growth can be stunted, seed production lowered, commercial value destroyed, and in extreme cases mortality may occur.

Residential Recommendations

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On large trees, parasites and predators usually keep pine tortoise scale populations so low that they are usually not a nuisance. Sometimes when insecticides are applied for another pest (such as fogging for mosquitoes or coneworms), parasites and predators of the striped pine scale are killed, but the scales survive and then reproduce unhindered by natural controls. Ants frequently tend pine tortoise scale to obtain honeydew excreted by these insects. It has been suggested that controlling ants may help limited pine tortoise scale populations because ants kill predators of the scales.

Sevin or one of the pyrethroid insecticides marketed in the big box stores should give more than adequate when applied to the crawler stage. If Sevin is used, I recommend using a sprayable formulation. Treat thoroughly after the crawlers have emerged. The crawler stages of Toumeyella scales usually occur in late May. Sometime in early May, it would be a good idea to put a small amount of infested plant material into a clear plastic bag. The bag should be place outdoors in the shade and examined every few days. If the tiny crawlers are noticed crawling about inside the bag or on the needles that would be a very good time to apply Sevin or a pyrethroid. Insecticidal soaps and horticultural oils may be used in late fall or early spring to treat overwintering females. These compounds will usually not harm beneficial insects. Good coverage is essential.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology

Find more information at the following NC State Extension websites:

Publication date: April 19, 2016
Revised: Oct. 10, 2019

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