Pine sawfly reaches 'epidemic' levels, defoliating ponderosa pines south of Denver

DENVER - The Colorado State Forest Service warns a bug that eats the foliage off ponderosa pines has rapidly reached epidemic levels south of Denver.

The outbreak of pine sawfly is believed to have begun near the border of El Paso and Elbert counties, Colorado State Forest Service spokeswoman Lisa Mason wrote in a news release. Residents in that area should expect to see the trees in that area defoliated and large numbers of larvae in the trees or on the ground beneath.

Mason wrote that experts with the Colorado State Forest Service and USDA Forest Service are monitoring the outbreak. They believe many of the larvae are depleting their food source before they mature and therefore will not be able to pupate.

"This outbreak is exceptional, possibly due to an unusually large number of eggs deposited on pine needles by adult sawflies last fall," Mason wrote. "What environmental factors may have accelerated this spike in the sawfly population is unknown."

Those that do survive long enough, however, will drop from their trees to pupate in the upper level of the soil.

Mason explained in her release that the most effective time of year for control measures including insecticides has passed.

To map the impact of the bugs on the trees, Mason said aerial surveys will assess the defoliation. Additionally, they will track egg deposits from the pine sawfly in the fall to help predict the potential for damage during 2015.

For more information from the Colorado State Forest Service, visit or contact the CSFS Franktown District at 303-660-9625.

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