Bald Cypress Rust Mite
The bald cypress rust mite, Epitrimerus taxodii, is also known as the swamp cypress rust mite. It attacks only bald cypress trees. This mite overwinters as plump, reddish females tucked into the crevices of the bark. After the new leaves form, overwintering females crawl out to feed and lay eggs from which hatch pale, slender mites -- males and females -- that infest the needles during the growing season. Rust mites rasp through the needle surface with their microscopic, scissor-like mouthparts and extract the cell contents below. As warm weather arrives, the mites reproduce rapidly until thousands can be found on a single leaf. Just visible with a 10-power hand lens, their numerous, white, cast skins are the easiest diagnostic sign to see. The summer mites are cream to very light brown. The last generation on the needles develops into the all-female, reddish, overwintering form.
Bald Cypress Rust Mite on Bald Cypress
Bald cypress rust mites feed only on bald cypress. Heavy populations cause the needles of the leaves become yellowish and then reddish brown. Trees heavily damaged early in the growing season should be treated (if practical).
Unfortunately, bald cypress is very sensitive to horticultural oils. If you control this mite with oils, you'll do more damage to the tree than the mites! Try carbaryl (Sevin) or some other miticide to knock down this mite. Thorough coverage of the foliage is necessary. Unless these rust mites are completely out of hand, the Missouri Botanical Garden recommends not treating at all because pesticides also kill natural predators of other bald cypress pests.
- An Illustrated Guide to Plant Abnormalities Caused by Eriophyid Mites in North America. Keifer, H. H., et al. 1982. USDA ARS Agr. Handbook No. 573. 178 pages.
- Bald Cypress Rust Mite. Nixon, P. and D. Shetlar. 1998. Home, Yard & Garden Pest Newsletter. Univ. Illinois Extension.
- Rust Mites on Cypress. Gowans, M. 2013. SFGate, Home Guides.
- Extension Plant Pathology Publications and Factsheets
- Horticultural Science Publications
- North Carolina Agricultural Chemicals Manual
For assistance with a specific problem, contact your local Cooperative Extension Center
This Factsheet has not been peer reviewed.
Publication date: Nov. 9, 2013
Revised: Oct. 9, 2019
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