The yellow headed sawfly affects spruce trees and is native to North America.
What are the Risks?
This pest attacks the needles of spruce trees. Young and open-grown trees are especially vulnerable. Larvae will feed on new needles and work their way to older ones. Eventually, the stripping of needles will weaken the tree, and can kill the tree if attacked for 2 or 3 years in a row.
What to Look For
Larvae will first appear in mid to late June.
Mature larvae Larvae damage
Mature larvae are about 20 mm long. They look like a hairless, green caterpillar will stripes along the body and a distinctive yellow/orange head.
Prevention
The best way to prevent severe damage is to conduct regular inspections. If you catch the infestations when they are small, you can hand pick or hose off the larvae with a strong jet of water.
Insecticides may be used to help protect larger trees.
Related Links
Yellow-Headed Spruce Sawfly - Gov of Canada