Integrated Pest Management
Ash Flower Gall and Cottonwood Catkingall Mites
Eriophyes fraxiniflora; Eriophyes neoessigi
Eriophyid mites (Whitney Cranshaw, Colorado State University, Bugwood.org)
Ash flower gall mite damage to male flowers (Steven Katovich, USDA Forest Service, Bugwood.org)
Galls left by cottonwood catkingall mites (Whitney Cranshaw, Colorado State University, Bugwood.org)
Pest Description
- minute; four-legged, cigar-shaped mite; white to yellow
- microscope or hand lens required to see mites; use symptoms for identification
Host Plants, Diet & Damage
Ash Flower Gall Mite
- found on the flowers of male ash trees
- swollen masses of fused male flowers remain green throughout the growing
- season
- brown, lumpy galls are noticed after leaf drop and are present from year to year
Cottonwood Catkingall Mite
- colonize catkin flowers on Freemont cottonwood and other cottonwoods
- produce wrinkled/curled catkins that hang grapelike
- galls present until mid-summer (healthy catkins fall in spring)
- new galls are green but eventually turn brown
Biology, Life Cycle & Damaging Life Stage
- overwinter in budscales
- emerge from budscales in spring just prior to budbreak
- migrate from buds to feeding sites in spring
- migrate back to buds in the fall
- immatures and adults are damaging
IPM Recommendations
- Damage is aesthetic; tolerate pest.
- Apply horticultural oils at budbreak to target migrating mites.
- Apply an insecticide (avermectin; carbamate; METI acaracide; insecticidal soap; lime sulfur; tetronic and tetramic acid derivatives) at or just prior to budbreak.
- Do not use horticultural oils in combination with, or within 30 days of applying sulfur or a sulfur-containing product.
For more information, see our Eriophyid Mites fact sheet.