Integrated Pest Management

Leafcurl Ash, Woolly Apple and Woolly Beech Aphids

leafcurl ash aphids

Leafcurl ash aphids and damage (James Solomon, USDA Forest Service, Bugwood.org)

woolly apple aphids

Left: Woolly apple aphid colony (Whitney Cranshaw, Colorado State University, Bugwood.org); Right: Long-term damage to apple tree (H. J. Larsen, Bugwood.org)

woolly beech aphids

Woolly beech aphids and damage (Louis-Michel Nageleisen, Department of Forest Health, Bugwood.org)

Pest Description

  • small, ~ 1/8 inch; pear shaped; color variable depending on species
  • bodies covered in a white, waxy filament that gives a cottony or woolly appearance (more apparent on some species than others)

Host Plants, Diet & Damage

  • cotoneaster, hawthorn, beech, ash, crabapple, firethorn, elm, etc.
  • attack roots, trunks, limbs, leaves and shoots
  • white, waxy substance can build up on plants
  • some species curl, twist, or cup leaves or feed on roots
  • honeydew or sooty mold may be present

Biology, Life Cycle & Damaging Life Stage

  • some have alternate hosts; others migrate between different parts of the same plant
  • overwinter as immatures on roots or as eggs on bark
  • emerge in spring and move up trunks to feed on leaves
  • mid-summer through fall, aphids migrate back to ash roots to overwinter
  • when aphid populations become high, winged aphids will fly to nearby hosts
  • winged adults may emerge from the roots in fall to mate

IPM Recommendations

  • These aphids have little negative effect on tree health; tolerate pest.
  • Monitor bark, branches and undersides of leaves for aphids in the spring.
  • Waxy coating and protection from curling leaves make cover sprays less effective.
  • Apply a systemic insecticide (neonicitinoid) in the spring.