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What is Cottony Ash Psyllid?

Is an invasive insect that has been found in several Manitoba communities. This insect is thought to originate from eastern Europe. The CAP infects Manchurian ash trees and Black ash trees. It is not known to occur or cause damage to green ash.


The adults are small (3mm in length), have yellow and black markings resembling large aphids. They can jump and have clear wings with shading towards the tips.

Sign and Symptoms

  • thinning in the upper portion of the tree


  • browning, yellowing and curling along the edge of leaves indicating a first-generation psyllid population


  • curled and misshapen leaves


  • a cottony substance found within the curled leaves indicating a second-generation psyllid population


  • heavily damaged leaves can have a cauliflower appearance


  • leaves may drop prematurely Over time, their presence will weaken the ash trees, making them vulnerable to other illnesses and predisposing them to premature death.

Prevention - What you can do by yourself

  • 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.

Watering & Fertilizing

Cottony Ash Psyllid

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