Bald Cypress Rust Mite

How to identify it

• The mites are just visible with a 10-power hand lens; overwintering females are plump and reddish, and summer mites are pale and slender.^[1]
• Their numerous white cast skins on the needles are the easiest way to diagnose them.^[1][2]

Where it lives

Found wherever bald cypress is planted, including North Carolina and Arkansas.^[1][2]

Biology and life cycle

Females overwinter in bark crevices and come out to feed and lay eggs once new leaves form.^[1]

In warm weather they multiply rapidly, until thousands can be on a single leaf.^[1][2]

Damage and signs

• Needles turn yellowish, then reddish or rusty brown; serious infestations can turn the whole tree rusty brown.^[1][2]

Health risk

None to people or pets.^[1][2]

Control

Biological control

Unless the mites are completely out of hand, NC State notes the Missouri Botanical Garden recommends not treating, to spare predators of other bald cypress pests.^[1]

Pesticides

Do not use horticultural oil: bald cypress is very sensitive to it; carbaryl, abamectin or insecticidal soap with thorough coverage control the mites.^[1][2]

Related profiles

• Hemlock Rust Mite
• Spider Mites
• Privet Rust Mite

Common questions

Why is my bald cypress turning brown in summer?

Bald cypress rust mites are a common cause; look for white cast skins on the needles.^[1][2]

Can I use horticultural oil?

No; bald cypress is very sensitive to oils.^[1][2]

Sources

1. NC State Extension, “Bald Cypress Rust Mite (PDIC Factsheet).” content.ces.ncsu.edu/bald-cypress-rust-mite-1 (accessed 2026-10-16)
2. University of Arkansas Division of Agriculture Cooperative Extension Service, “Baldcypress Rust Mite (Plant Health Clinic disease notes).” www.uaex.uada.edu/yard-garden/plant-health-clinic/disease-notes/posts/baldcypress-rust-mite.aspx (accessed 2026-10-16)
3. iNaturalist, “Epitrimerus taxon page (order and family).” www.inaturalist.org/taxa/209214 (accessed 2026-10-06)