Cottony Ash Psyllid

Posted by shane - January 31, 2011 - Insect Pests, Insects, Diseases & Other Problems - No Comments

For information on the biology and control of this pest, please refer to the following link to the City of Red Deer Fact Sheet:

Red Deer Experience

This pest has been tough to control.  Most Black and Manchurian Ash in Red Deer in 2009 were in decline or nearly dead.  In 2010, likely due to a cold, wet spring and early summer, pest populations appeared to be much lower and many trees appeared to be “bouncing back.”  Since 2011, most trees have continued to decline, and in 2013 these were the most common trees that we removed and replaced.  Calgary has very few of these trees left, and no sensible arborist would recommend that any client plant a new one.  My feelings are the same.  I reccomend planting something that is insect and disease resistant.  Please call or email me for suggestions.

Control Measures

There are two generations per season for this insect.  Over the past four seasons, I have been injecting the trunks of infested trees, in the first week of June, with Confidor (imidacloprid).  So far, I’ve found that the chemical is keeping most of these trees alive, but that’s it.  Injected trees have not returned to a vigorous state.  I also have found that the chemical is only effective with established trees.  Confidor does not seem to control psyllid on newer trees, with poorly established root systems.  For these trees, I recommend removal.  For larger, established trees, I recommend chemical control, followed by pruning to remove the unsightly, dead branches.  We are likely fighting a losing battle with this pest, and unless you are prepared to spend some money to control the insects, I suggest you plant something else.

UPDATE 2013:  The past three seasons, I also tried spraying the leaves with systemic insecticides at different intervals, with little success.  Some people tell me that they’ve read on the internet that you can control this pest with chemicals.  Well, this blog is on the internet too, and I can tell you from experience that the controls don’t work.  You’re better off with a healthy, new tree.