Are the needles on your pine tree partially chewed or totally missing? The pine sawfly larvae may cause this. They are one of the first insect pests that appear in the spring. The larvae are caterpillar-like with a shiny black head and a greenish yellow body.
The sawfly larvae hatch from eggs that are laid by a clear-winged, non-stinging wasp. They feed on many types of pine trees. They generally feed on the outer needles first and then feed on other needles. Small trees may be completely defoliated. This is especially harmful to young trees.
Pine sawfly generally congregate in colonies on the tree. They should be treated as soon as they are noticed to reduce damage to the tree. You can use a strong stream of water to knock them off and destroy them or spot treat with an insecticide labeled for pine sawfly control. Contact your county extension office, master gardener hotline or local nursery for insecticide recommendations.