Damage to Ponderosa Pine Plantations by the Western Pine-Shoot Borer

Larval mining by the western pine-shoot borer, Eucosma sonomana Kft., stunts the height of infested leaders and impairs growth of the next year's leaders. The loss in average annual height increment is estimated at up to 25 percent of borer-unaltered increment and may result in similar losses in volume yields. Surveys in young pine plantations show increased incidence of infested leaders with increasing xericity of habitat types.