Colorado pine needle scale infestation raises concerns
It has been said that every solution creates new problems. For local foresters that statement is especially poignant.
For the past several years state, local and federal agencies have focused on mitigating the threat posed by pine beetles. Those efforts may have created prime conditions for the proliferation of another invasive and harmful insect species, pine needle scale.
“The concentrated spraying for mountain pine beetles may have contributed to the build-up of this insect,” said Ron Cousineau, district forester for the Colorado State Forest Service Granby District, “by killing beneficial parasitic insects that would normally keep scale populations in check.”
Last week officials from the State Forest Service office in Granby issued a statement regarding their growing concern about pine needle scale infestations in the area. Pine needle scale, not to be confused with pine beetles, is a native insect that feeds on the needles of most species of pine, spruce and fir trees. According to the State Forest Service, pine needle scale is on the rise in Grand, Summit and Eagle counties.
Local foresters are working on plans to mitigate the infestations. At this time they caution against further chemical spraying.
Pine needle scale can affect both mature and young trees. The insects primarily attack older trees but if infestation in an area becomes thick enough the scale will begin moving to younger trees. The bugs themselves reside under waxy white structures on pine needles. Female pine needle scale lay eggs under these waxy structures.
After the eggs hatch they transition into a “crawler” phase. During the crawler phase the immature pine needle scale will begin crawling in search of new pine needles. It is during the crawler phase that pine needle scale is most susceptible to mitigation efforts. The crawler phase for this year’s hatching of pine needle scale occurred roughly three to four weeks ago and is now completed.
“Periodic needle scale infestations are a common occurrence in Colorado’s mountain forests,” according to the statement released last week. “They typically have minimal impacts, very limited geographic scope and are short-lived, lasting one to two years.”
The release goes on to explain that evidence of the current infestation in the area is both widespread and has endured for the past four to five years in certain areas.
“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 Cousineau. “We have never seen pine needle scale become this damaging in this part of the state.”
Pockets of infestation have been found in lodgepole pines in the Fraser Valley, blue spruce filled mountain valleys near Vail and small pockets in Summit County. Infestations appear to be heaviest in areas within or adjacent to locations heavily sprayed for mountain pine beetle over the past decade.
Predatory beetles, parasitic wasps, and other natural enemies of pine needle scale help keep their numbers in check. Impacts of scale infestations can be mitigated by using horticultural oils or insecticides if applied at the appropriate time of year to coincide with pine needle scale’s “crawler” development stage.
Pine needle scale feed on pine needles, weakening the trees and causing needle drop and dieback. Scale infestations also weaken the trees, making them more susceptible to other pests and diseases. Pine needle scale-covered needles look as though they have bee splattered with white paint.
For more information about pine needle scale or how you can work to mitigate infestations contact the State Forest Service Granby District at 970-887-3121.
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