Saturday, April 16, 2011

Pest Problems Abound After a Dry Fall and Winter by Mary Small

We’ve sure had a dry fall, winter and early spring! And alas, as I write this, I can hear the wind roaring outside.  Our persistent dry, warm, windy weather has stressed plants and this will make them susceptible to disease and insect pests in 2011. Many tree care specialists think there will be a lot of damage this year.

Here are a few problems we can expect to see:
CSU Extension

Winter burn on evergreens. 
In fact, you can see it now. Look for brown needles, particularly on the south or on the windward side of the plant. Needles will be uniformly brown from the tips inward.  It’s the result of our dry, warm, windy weather that promotes transpiration, water loss through the needles. This isn’t a problem until there’s not enough water in the soil to replace what gets lost. Sometimes, though, water loss happens so fast (like on windy days!) that plants  cannot keep up with it. Needles lose so much water so fast, they dehydrate or “burn”. 
Little can be done at this point, except to water plants and hope for rain or snow! This spring’s new growth will mask most of the brown needles which will eventually fall off. Winter burn does not usually kill established plants, but may seriously damage younger ones.

University of Minnesota Extension

 Cytospora canker. 
A common fungal disease found on many trees and shrubs.  While the problem is a common one, we will probably see more because of weather stresses.  This pathogen is a weak one and only successfully damages plants stressed from something else, like drought. Look for dead or poorly leafing branches this spring and examine them more closely for sunken, discolored lesions.  These are the cankers. Prune damaged branches off below them. Water trees every 2-4 weeks if there’s no significant snow melt or rainfall.  For more information on Cytospora canker management strategies, see fact sheet 2.937, Cytospora Canker at

Borers and bark beetles that attack stressed plants. 
When trees are stressed, they produce chemicals that can attract certain insect pests. An example of this is the spruce ips beetle. Spruce ips beetles feed in the conductive tissue under the bark, causing needle and branch death. They are typically found in the upper portion of mature trees. They also damage recent transplants.  Actively growing, healthy trees are more resistant to insect pests.  Promote  plant health by watering during dry periods, but avoid over-irrigation as that  stresses trees, too.  Insecticide treatments may be applied to trunks just prior to the time when adults fly and begin laying eggs in the spring.  For more information on ips beetles see: