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Linda Joyce
Rocky Mountain Research Station
240 West Prospect
Fort Collins, CO 80526
Phone: 970-498-2560
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Pine Beetle Evidence      Go Back!
Discolored foliage in late Spring is a sign that ponderosa and lodgepole pine trees have been killed by the mountain pine beetle. These trees are called 'faders' and/or 'flag trees' (slide credited to Jose Negron).



Reddish pitchtubes (resin mixed with frass), on the tree trunk and reddish boring dust at the base and also in the bark crevices of the tree, are good indicators of a successful beetle attack (slide credited to Jose Negron).

Unsuccessful beetle attacks are identified by large white pitch tubes on the tree trunk. These resin tubes may have an embedded adult beetle. Coarse frass can be found at the base of the tree. No blue-stain is present and the foliage is green.

Woodpecker damage on beetle infested trees is very noticeable. They make individual holes in the bark as they search for and feed on beetle larvae. Woodpeckers will pick out the best brood producing tree and therefore are good indicators of beetle attacks (slide credited to Jose Negron).

The sapwood of an infested tree will be discolored by a blue staining fungi; the heartwood will not be stained.

Exit and entrance holes are evident on the bark. Entrance holes will be visible during the attack period and exit holes will appear the following emergence period (slide credited to Jose Negron).
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