Steely-blue wood wasp - Sirex juvencus L.From: Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests Occurrence: Europe, Siberia, Sakhalin Island, Japan, Philippines and Algeria. Introduced with wood products to the New Zealand. Host Plants: The Norway spruce, rarely Scots pine, larch and common fir. Recorded on Abies concolor introduced to Poland. Morphology: Male adults are 8-28 mm long, and females are 15-32 mm long. A few basic segments of antennae are reddish, and others are brown or black. Sexual dimorphism is clear. The female body is black-bluish with metallic shine. Legs are yellow-reddish. Femora and trochanters are reddish-brown. The last abdominal segment is triangle and wide in a basal part. Ovipositor is as long as abdomen or slightly longer. The male body is black with metallic shine. Front and middle legs are reddish with black femora and trochanters. Hind legs are black with red femora, the base of tibiae and the last segments of palpi. The abdomen is red with the black-bluish first and second tergits, first sternit and last segment. There are brownish spots sporadically occurring on the bases of other abdominal segments. The egg is white and elongated. The larva is cylindrical, white, up to 40 mm long. The pupa is yellowish-white, slightly S-shaped. Biology: Adults fly from July through August. After mating, females deposit 1-5 eggs into the hole drilled in the wood with ovipositor. Each female produces about 100 eggs. Larvae feed first in the wood, close to the hatching place, but in mid-summer they tunnel deeper into the wood, 15-17 mm below the surface. After overwintering, they continue feeding in sapwood in April. Then larvae make horizontal tunnels filled with shredded wood. Before pupation, they tunnel 18-70 mm under the wood surface and construct pupal chambers at the end, where they overwinter. Total larval tunnels are 80-230 mm in length. Pupal chambers are oval, 15-30 mm long and always directed perpendicularly to fibers and wood surface. Larvae pupate in summer. Adults chew to the surface and leave the tree through exit holes of 4-6 mm in diameter. This species has one generation per 2 years, rarely 3 or 4 years. Damage: S. juvencus is an important technical pest of timber that decreases the value of the wood. It prefers stands damaged by wind, fire, pathogenic fungi or snow. Sometimes, the density of tunnels reaches 40 per 1 m of the tree stem. This insect infests wounded, weakened or dying trees, windthrows and timber. It also spreads symbiotic, wood attacking fungi. Control: Similar to U. gigas.
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Forest Pests: Insects, Diseases & Other Damage Agents |
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