Check your spruce for yellow-headed spruce sawfly
About the time the lilacs are in full bloom in your neighborhood, yellow-headed spruce sawfly adults will be flying around and laying eggs on white spruce needles The adults prefer to lay their eggs on trees that are in sunny locations, most commonly, on the terminals of open-grown seedlings. Tiny larvae will hatch from these eggs from seven to fourteen days later and begin to feed on the new needles, leaving only short brown stubs in their wake.
The best place to look for the larvae is on trees that the yellow-headed spruce sawflies fed on last year. The best time to look, in most of northern Minnesota, is during the first three weeks of June. If you don't find them the first time, check again a week later. Don't wait until the defoliation is obvious through your neighbor's kitchen window. Small numbers of larvae can be hand picked off the trees but lots of larvae on lots of trees will require chemical control. High sawfly populations or repeated years of defoliation not only make the spruces look bad but can also kill them.