Friday, May 22, 2015

Sawflies population boom killing ponderosa pines

With significant portions of Colorado experiencing conditions that are abnormally dry to severe drought (Drought Monitor), and tree defenses down due to the drought, a population boom in pine sawflies (Neodiprion autumnalis) has become another stress on ponderosa pines in the west.  In 2014, pine sawflies defoliated 7,400 acres of pine forests and a sawfly egg survey predicts another year of moderate to heavy defoliation.  The sampling plan is based on one developed in New York for a different species of sawfly and pin, and it may not quite fit the situation for Colorado.

pine sawflies (Neodiprion autumnalis) by USDA Forest Service - Region 2 - Rocky Mountain Region Archive, USDA Forest Service,

This is Colorado's first attempt at predicting the defoliation by pine sawfly by egg counting, and if it is successful, it could be used to generate a model for future outbreaks.  As chemical controls should be applied at egg hatching, the plan can help inform applicators of where the heaviest infestations are likely to occur.

Denver Post: Sawfly wasp outbreak spreading through Colorado's ponderosa pines
Colorado State Forest Service: Pines Southeast of Denver Expected to Suffer Damage from Sawfly this Summer
Franktown District, CSFS: Potential for Pine Sawfly (Neodiprion Autumnalis) Defoliation of Ponderosa Pine Forests in Elbert County, CO, in 2015