Look for tiny larvae of Yellow-headed spruce sawfly feeding on tender new needles of spruce (e.g. Colorado spruce) in the landscape. Plant phenology indicator: Robinia pseudoacacia (black locust) in full bloom. Larvae are green with lighter longitudinal stripes, yellow-brown heads. There are several insecticides registered including Dragnet, Dylox, Pounce and Success to target young larvae. This is a damaging pest of spruce just north of Toronto and has caused significant damage to spruce trees.