Hello Folks!

I've got an interesting problem with borer larvae in Black Cottonwood (P. trichocarpa) in a residential landscape.
This problem goes back over a year ago, when I first obtained samples of both larvae and pupae.
So far, no positive ID has been established from all levels and sources of both private and government experts.

So I'm taking a chance with the Knothole site.

The larvae are similar to Carpenter Moths of the Family Cossidae in the Order Lepidoptera. Particularly the Carpenterworms
(Prionoxystus robiniae) yet they lack the distinctive, dark brown "tubercles" on the body. They do not pupate in the tunnels
near the surface. They pupate in the surrounding soil encased in a 1-2" long, silk-lined, "coocoon" of debris. In addition,
there are no traces of sawdust from any of the tunnels, and feeding is confined only to the root collar and major lateral roots.

The larvae abdomen lacks the short "horn" on the tip, typical of the Pigeon Tremex or PT (Tremex columba). Also, PT's are not found
in the Western provinces, yet the "coocoons" are very similar, with the exception of the pupating sites. Pt's pupate underneath the bark, while our
specimen pupates in the surrounding soil.

Here's the challenge. Who can identify this borer, wasp or moth? Unfortunately, no pupa were successfully "grown" into adults by our local University entomology professor!
Have at her, everbody! Hope to find a positive ID!

DgM

Reply to post by Dave G Meadows, on November 30, 2000 at 20:48:54:

This sounds like it might be *Prionus laticollis, broadnecked root borer. Feeds on many hardwoods, including poplar. Larvae may be up to 3 inches, move from root to root through soil, and pupate in the soil. Life cycle 3 to 5 years.

They can hollow out the root, severing it completely.

USDA forest Service, Misc. Pub. #1426 Insects of Eastern Forests, p 309

Reply to post by Russ Carlson, on November 30, 2000 at 20:48:54:

Thanks Russ!

I'll have a look at this species of borer. Do you know if it has an extended range covering the West and Midwestern regions?

Reply to post by Russ Carlson, on November 30, 2000 at 20:48:54:

For mor info, here is the searh I used

http://search.dogpile.com/texis/search?q=Prionus+laticollis&geo=no&fs=web

Reply to post by JPS, on November 30, 2000 at 23:42:27:

JPS:

Thanks! I found this site also, but from the image provided, the Prionus larva shown has a large "swollen" thorax. I'll try to obtain a JPEG file for some of the photos I have taken and I'll post them FYI.
Thanks!
DgM

Reply to post by Dave G Meadows, on November 30, 2000 at 23:42:27:

The book says Eastern US, but many of the more obsucre insects have broader ranges that might not be reported. Anyway, this might at least give you a start on the ID.