Cottony Ash Psyllid

Psyllopsis descrepans Flor 1861

Cottony ash psyllid (CAP) is a non native insect that has been found in Manitoba in Morden, Winkler and Winnipeg. Surveys to find additional infestations are ongoing. CAP is thought to originate from eastern Europe and occurs on Manchurian and also black ash. This insect has been reported in Alberta (Edmonton, Calgary, Red deer), Saskatchewan (Saskatoon) and North Dakota.


Adults are small, 3mm in length with yellow and black markings and resemble large aphids. Wings are clear with shading towards the tips. Adults jump.


The insect overwinters as eggs in the crotch between twigs and buds. The eggs hatch in the spring at the time of bud break and feed on expanding leaves. Feeding by the insect during the immature stage causes the leave to curl. The immature insects (nymphs) extrude a white cottony substance.

The eggs of the second generation are laid on the midrib of the top of leaves and typically hatch in mid-July.The second generation nymphs feed in the curled leaves that were created by the first generation. Nymphs of the second generation change to adults in early August.


Black (Fraxinus nigra) and Manchurian ash (Fraxinus mandshurica) and hybrids of these two species are susceptible to CAP. It is not known to occur or cause damage to green ash (Fraxinus pennsylvanica).

Signs and Symptoms:

  • Thinning in the upper portion of the tree
  • Browning, yellowing and curling along the edge of leaves
  • Leaves can be curled and misshapen.
  • A cottony substance can be found within the curled leaves
  • Heavily damaged leaves can have a cauliflower appearance
  • Leaves may drop prematurely


Management Options

  • Psyllids are difficult to control, because they are hidden under the curled leaves for a large portion of their life cycle.
  • Drought stressed trees may be more vulnerable to damage from this pest. Keeping trees healthy by watering and avoiding additional stresses could help reduce CAP impacts.

Insecticide treatments may be available. It is best to get quotes from a licensed arborist for possible treatment options.