Ponderosa pines being chewed by the western pine budworm


Mature ponderosa pine trees are one of the dominant trees both in our forests throughout Archuleta County and in our backyards. This year, the new growth of many ponderosa pines is being chewed by an insect called the western pine budworm, choristoneura lambertiana.

This insect will feed on limber, lodgepole and ponderosa pines and some white fir if mixed into a stand of lodgepole pine.

Eggs hatch in late summer and the tiny larvae do not feed, but migrate to sheltered overwintering sites in branch and stem crevices. The larvae molt once and then hibernate through winter within silken shelters they spin around themselves. Larvae emerge in spring when shoot development is nearly complete, mining needle sheaths, old needles and developing cones.

As they grow, larvae feed on new, elongating needles. However, in some cases, larvae may continue to feed primarily on male and female cones. One to five larvae per shoot will web new needles together and feed in this protective enclosure, which becomes littered with droppings and brown, partially chewed needles. Larvae pupate in these loose silk and needle enclosures and emerge as adults in July and August. Eggs are deposited on the concave side of older needles, preferentially in the upper crown, hatching two or three weeks later.

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