Sunday, August 2, 2015

Yellow-Headed Spruce Sawfly infestation in Pincher Creek continues

Photos: Sawfly infested trees in Pincher Creek, late July, 2015 (except *)

In early July the Town of Pincher Creek issued the following advisory:

Residents of Pincher Creek, 

Pincher Creek is currently being affected by an infestation of the Yellow-Headed Spruce Sawfly. Please check your spruce trees for this worm like insect (larvae) that resembles a small caterpillar. 

* Photo courtesy of Government of Alberta Agriculture and Forestry and A. Bamber, CARA
The mature larvae are 16-20 mm in length, dark glossy green with lighter stripes down the sides and a head that is reddish-brown in color. The larvae eat the spruce tree needles on the branches and the upper crown of the tree may appear bare. Control measures should ideally begin in mid-June. Non-chemical control measures include hand picking of the larvae, especially if numbers are small. Or you can try using high pressure sprays of water to remove the larvae from the tree. Insecticides may be less effective now as the larvae are close to full grown. Any chemicals should always be used with caution and according to directions on the product.

Photos: Sawfly infested trees in Pincher Creek, late July, 2015

Generally the vigor and growth of the tree will be affected the following year. Severe defoliation can lead to top kill of trees and repeated defoliation of needles over a 3-4 year period can lead to mortality of the tree.

Trees affected by this insect include Black and White spruce, Colorado spruce, and Norway Spruce. Trees over 3 years of age, those out in the open or the end of a row and in full sunlight are often targeted.

Let’s do our part to keep our communities trees healthy!  

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