Yellow Headed Spruce Sawfly – Pikonema alaskensis

Yellow Headed Spruce Sawfly – Pikonema alaskensis Scientific Name: Pikonema alaskensis Common Name: Yellow Headed Spruce Sawfly Distribution: This sawfly may be found from Alaska to Maine in the United States, and it is present across the spruce range in North America. Host plants: All native Alaskan spruce species as well as the majority of foreign ornamentals, including Norway and Colorado blue spruce, are targeted by the yellow-headed spruce sawfly. Identification: The mature yellow-headed spruce sawflies are tiny, 1/3-inch-long, stingless wasps. Since larvae easily blend in with spruce green needles, a detailed examination of the branch or shoot is required. Larvae will drop onto a white sheet of paper if you place it beneath a branch, shake it, and let the shoots to fall on it. Larvae are 4-6 mm long and whitish in the early stages. When fully grown, the larvae have green bodies with six striped patterns and brownish-orange heads. When fully grown, larvae fall to the earth and spend the winter underground in cocoons. Every year, the sawfly completes one generation. The adult sawfly is tiny (8–10 mm), reddish brown, and resembles a wasp. Life Cycle: Just as the buds on spruce trees start to grow in the spring, adult yellow-headed spruce sawflies appear. Single eggs are laid by females on the base of newly growing needles. In two weeks, the larvae emerge and start eating the succulent needles. The larvae reach full size in early to mid-July, measuring around 20 millimeters (mm) in length. When fully developed, larvae have green bodies with six greyish-green stripes and brownish-orange heads. When fully grown, larvae fall to the earth and spend the winter underground in cocoons. Every year, the sawfly completes one generation. Damage: Young larvae lose the tissue that is most actively photosynthetically active because they only eat the needles of the current year. Older larvae go on to the needles from prior years once the fresh growth has been consumed. The higher crowns of infected trees initially show the most damage, with the remaining, partially eaten needles giving the tree a ragged, brownish look. The entire tree may lose its leaves as the larvae feed on the older foliage. A single year of severe defoliation reduces shoot and needle growth; two or more years of severe defoliation may induce top kill, branch dieback, and maybe even the death of the tree. Management: Remove the caterpillars by hand from smaller trees that have mild infestations and dispose of them. It works well to hard-spray them off the tree with regular old water. Little caterpillars can’t make it back up the tree. Crush bigger caterpillars that fall from the tree with your foot. Remove aging needles from under the tree to prevent further growth. The larvae of sawflies are naturally preyed upon by beetles, rodents, some insect parasites, tachnid flies, and viral infections.