Pine bark borer??? #594231 - Ask Extension

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Pine bark borer??? #594231

Asked September 03, 2019, 5:30 PM EDT

Yesterday I noticed dozens of webs on our beautiful white pine that we planted 30 years ago. In one of the webs I found a dead beetle, 1 cm long with an iridescent body of 3/4 cm. There are multiple bb-sized exit holes in the trunk and seepage of sap where branches used to be. The tree looks healthy otherwise (see photo). I did some detective work and found similar issues on a nearby Norway pine which looks less healthy but has always been kind of a scrawny tree. In fact nearly all of the pines on our property, even the very old ones, have at least some exit holes. However just the two trees have a significant amount of sap leakage and webs. Will appreciate information and suggestions. Photos attached. Thanks, Karen and Howard Stone

Itasca County Minnesota

Expert Response

Hello. I'm glad you've turned to AaEx.

Webs are not part of the biology of pine bark borer but the small bb-sized holes are suspicious. It helps that we have not been in a drought for a few years so that the trees have been able to produce sap that keeps the pine bark borer in check.  The dead insect is not a pine engraver beetle that is the culprit behind the borers.

Here is more information about pine bark borers that may be of help to you: https://extension.umn.edu/forest-pests-and-diseases/managing-pine-bark-beetle-damage

As for the webbing - have you found the webs at the base of needles? If so, it could be pine false webworm. These little green caterpillars feed from May to June so you may not see anything in the nests now.  If you have a large infestation, you may want to consider hiring a certified arborist next spring to deal with the worms when they're feeding. Here is some information about pine false webworm: https://www.canr.msu.edu/news/pine_false_webworms_are_active_in_scots_pine

Here is a link to information on how to find and hire a certified professional:

https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional

I hope this information helps.
Ellen Campbell Replied September 04, 2019, 1:36 PM EDT

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