Attempts To Stop Mountain Pine Beetle Could Have Welcomed New Pests

In the last two decades, mountain pine beetles have devastated Colorado forests. Private land owners and localities sprayed trees to slow the spread of beetles turning mountain sides brown with dead evergreens.

Now, pine needle scale infestations are heaviest in areas within or adjacent to locations sprayed for pine beetle. That could be because the sprayings killed the parasitic insects that would normally keep the scale population in check. 

“These infestations have become so heavy and persistent in some areas that we are seeing many trees die with no other insect or disease influence," said Ron Cousineau, of the forest service's Granby District, in the report."We have never seen pine needle scale become this damaging in this part of the state.”

Small scale infestation are normal in Colorado, but they generally only last one or two years. Local foresters are now observing widespread outbreaks that have lasted four to five years in some areas.

Infested trees appear to be covered in white paint from the many scales feeding on the needles. The new color comes with a set of health problems for the tree. Pines and spruces infested with the insect are more susceptible to other insects and diseases. Resulting needle drop and dieback can also harm or kill trees. 

At this time, foresters caution against any further chemical spraying of impacted trees.