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Spruce Trees & Sawflies

  • July 10, 2013
  • Written by Andrea Early

The Yellow Headed Sawfly - A common larvae is causing damage to trees in Saskatoon right now. Although there are different species, the Yellow-headed Sawfly is the most common and a serious pest in our region.

The sawfly infests and feeds on spruce trees that are growing singly or on the edge of a group of trees. The larva resemble a caterpillar. You may notice complete defoliation of branches and twigs with only a few chewed brown needle stubs remaining. Repeated severe infestation over a three year period can kill trees.

You can spray the tree with a biological insecticide like BTK which has to be ingested by the larvae while eating which can last 30-40 days! A faster and more effective solution is to spray with Permethrin (Ambush) which is a low toxicity (to mammals) insecticide, works immediately, and can have a 7day residual...follow label directions. More than one application may be necessary especially after rainfall.