Other common name: European woodwasp
Scientific name: Sirex noctilio Fabricius
Native range: Europe, Asia and Northern Africa
Sirex woodwasps feed primarily on pines, including jack, eastern white, red, Scots, and Austrian pines. It also infrequently attacks spruce, larch, fir and Douglas fir. It prefers stressed trees, but can kill apparently healthy trees. Injury results from larval feeding and a toxic mucus and fungus injected into the tree when eggs are laid. Infestations have been documented causing up to 80% tree mortality.
Adult Sirex wood wasps are 1 to 1.5 inches long, lack the narrow ‘waist’ of other groups of wasps, and have a pointed plate-like projection extending from the tip of the abdomen. Females are metallic blue-black in color with orange legs. Males are similar to females, but the middle portion of the abdomen is orange and the hind legs are black. Larvae, which tunnel in wood, range from 0.04 to 1 inch long and are creamy white with a dark spine projecting from the abdomen.
In its native range, spanning from Europe and northern Africa to Mongolia and southern Russia, the Sirex wood wasp is generally considered a minor pest. In contrast, this wasp is considered a major pest in areas it has invaded, such as New Zealand, Australia, South Africa and South America. It has recently invaded North America where, as of winter 2006, it was detected in New York, Pennsylvania and Ontario.
Symptoms of attack
1. Trees with needles pointing downward (wilted) and crown turning light green to yellow to reddish brown
2. Beads of resin on bark (oozing from egg-laying sites)
3. Round adult exit holes (0.1 to 0.3 inch diameter)
4. Fungal stains (long, narrow and brown) running with the grain on sapwood
Contact the Minnesota Department of Agriculture via Arrest the Pest if you suspect an infestation of sirex woodwasp in Minnesota.