Sirex woodwasp

Sirex noctilio Fabricius

Sirex woodwasp is native to Europe, Asia, and northern Africa. It has been introduced to New Zealand, Australia, Uruguay, Argentina, Brazil, Chile, and South Africa as well as Indiana and New York. The most common method of introduction has been on solid wood packing material as well as in untreated or dried logs and saw timber. It attacks a wide variety of pines including Monterey, loblolly, slash and shortleaf. The female drills into the wood and inserts a toxic mucous and the fungus Amylostereum areolatum along with her eggs. The mucus prevents anti-fungal toxins from being formed at the site of infection. The fungus grows in the wood causing it to dry out and the trees die in a few weeks or months. The eggs are white, soft, smooth and elongate. Larvae are creamy white and legless with a distinctive dark spine at the rear of the abdomen. The frass-filled larval galleries become 'horseshoe' or 'u-shaped' as the larvae tunnel towards the heartwood, but then turn back towards the sapwood. Larvae feed on the fungus, which has converted the wood cellulose into a more easily digestible form. The pupae formed in the outer layers of the sapwood are initially creamy-white and gradually assume the color of the adults. In July, large round holes are left as adults emerge and begin searching for new hosts. The adult is a large, robust insect, usually 1 to 1 1/2 inches long. Adult females have dark metallic blue or black bodies with orange legs. The head and thorax of the males are metallic blue. The abdomen is orange at the center and black at the base. Sirex woodwasp is expected to complete one generation per year throughout most of the United States. The most important symptom is the progressive and irreversible chlorosis in the crown, followed by a sudden wilting of the foliage, heavy needle fall, and finally death and decay. Initially it is important to inspect the surfaces of stems for resin drops released after eggs are laid. Narrow bands of brownish fungal stain in the outer sapwood can be noted in infested trees. In general, Sirex woodwasp attacks living pines, while native woodwasps attack only dead, weakened, or dying trees.

Identification, Biology, Control and Management Resources

Pest Alert - USDA Forest Service
Pest Alert - USDA Forest Service
Sirex noctilio (Sirex Woodwasp) - USDA APHIS
Sirex Woodwasp: Description and Management Practices Guide for New York Forests - NYS Department of Environmental Conservation, Division of Lands and Forests