Cottony Ash Psyllid

Cottony Ash Psyllid (CAP ) also known as jumping tree lice is an invasive species. The pest originated in Europe and has been found in the US and Canada. CAP infests black, Manchurian and black-Manchurian hybrid ash trees but does have an affinity for stressed trees. Once a tree is infested it may recover, succumb to the pest and die or become more vulnerable to other pests and illnesses. It was confirmed in Winnipeg 2017 around the Forks area but has spread widely just in varying degrees. 14,400 black and Manchurian ash trees in Winnipeg could succumb to this pest.

CAP infestation Timeline from 2012 to 2017 at the Forks

When CAP eggs hatch the immature insects (nymphs) feeds on the  leaves sucking out the sap  which results in curled up leaves and a white cottony substance to be produced. The insect is thought to also inject the tree with a toxin which damages tree leaves. The pest is thriving in our hot summers and does not seem to be affected by the cold winters.

What to look for:

  • 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

What to do:

CAP has no natural predators and Winnipeg’s ash trees have no resistance to the pest. Neem oil trunk injection and pesticide sprays have no evidence to support the control of the pest. Pesticides have not been proven to be effective in the management of CAP because the leaves curl up preventing contact with the insects.  Insecticidal soap may work when applied frequently and with precise timing. The time to apply the soap mixture is dependent on the life cycle of the pest, you want to apply it at the early nymph life stage most likely first week of June and then again for the second-generation nymph the first week of July.

The best option for controlling this pest though is to try to keep your tree healthy. Eliminating the stress on your tree can be accomplished through proper watering, pruning,  and mulching around your tree. Trees may recover on their own if they are properly cared for and the infestation is not severe. An ISA certified arborist can assess your tree and help create a plan to treat/ manage your ash trees. For more information hiring an ISA certified arborist click here