Send Them Packing!

photo:USDA

Mega deals at the mega mart lead to increases in invasive forest pests. Improvements in transportation mean that a forest pest that laid eggs in packing crates on one continent can have its offspring delivered to the other side of the world just a few short weeks later. Add one more to the list of infamy that includes the Asian long horn beetle and the emerald ash borer.

The Sirex wood wasp is the latest unwelcome guest that has hitchhiked its ways to our shores in the cargo hold of high speed container ships.

Sirex noctilo F. is a native of Europe, Asia and Africa where it is considered to be a minor pest of stressed Scots pine. When it was accidentally introduced to pine plantations in South America it was no longer a bit player in the world of forestry.

In South American pine plantations mortality of up to 80% was recorded. Most of these plantations are planted with native north American trees such as Ponderosa, jack and lodgepole pine. White pine are less affected but are subject to attack.

In North America we have at least a dozen native wood wasps. Wood wasps are typically 1 to 2 inches in length, wasp like insects and generally are black and brown in color. The Sirex wasp has characteristics that distinguish it from the native species.

Sixex adults are generally blue to blue black with the males displaying an orange mid torso. The females have large reddish yellow feet which will be black on the rear legs of the males. The antennae on both the males and females are black.

If you thing you have spotted one please contact an expert for positive identification.

Native wood wasps attack dead and dying trees but Sirex wasps attack living trees.

The actual feeding of the larvae cause some of the damage, but a symbiotic fungus, Amylostereum areolatum that the female injects into the tree as she is laying eggs does the bulk of the damage.

The wasp completes its life cycle in one year. Adults emerge in mid to late summer and the females make an initial flight to a stressed tree. The females have been reported to travel up to 90 miles making quarantine efforts ineffective. Given that many trees are drought stressed at this time of year hosts will not be difficult to find. The female drills her ovapositors, a specialized egg laying appendage, into the bark of the tree and deposits up to 250 eggs and the symbiotic fungus under the bark of the tree. Fertilized eggs develop into female wasps, unfertilized develop into males. The larvae tunnel into the interior of the tree for up to a year. Pupae form close to the the surface before the adults emerge the following summer.

With the large number of two three and five needle pine in North American forests this pest is

expected to have a substantial impact.

Another hitchhiking newcomer, the emerald ash borer has just been located in Toronto, Canada as it continues to spread.