Cottony Ash Psyllid

Cottony Ash Psyllid is a relatively new insect in Calgary. Black Ash and Manchurian Ash are most affected. Eggs from the previous year hatch in June and nymphs feed until about mid-July. Now adults, they lay eggs in July and early August which hatch and the resulting nymphs begin feeding. When these second generation nymphs reach adulthood they will lay eggs on twigs to overwinter.

Tree Damage

  • The visible damage is curled leaves caused by the piercing and sucking of the nymph stage of the insect.
  • Inside the curled leaf there is a cottony material surrounding the insect.
  • In the process of feeding the nymphs also inject a toxin into the leaves.
  • Premature leaf drop and branch dieback are common.

Control Measures

  • Most treatment has been unsuccessful resulting in many trees dying from the insect.
  • Begin monitoring at bud break and start treatment as soon as nymphs or their cottony material is detected.
  • Contact an ISA certified arborist to discuss treatment options.