Host:  Ponderosa pine

Symptoms/Signs:  Newly hatched pine butterfly larvae are gregarious feeders on older foliage and then move to the new foliage as they mature. Mature larvae are approximately 2.5 cm long, dark green in color and have light green heads. The body is covered with fine hairs and has two white lateral stripes on the side. Adult moths are white with black markings.

Biology:  Adults fly and lay their green eggs from August through October. The eggs overwinter and the larvae hatch the following June or about the time new foliage appears. The small larvae feed in clusters with their black heads oriented toward the tip of the needle. As the larvae mature they feed singly. They pupate in late July for approximately 15-20 days.

Effects:  This insect has caused spectacular defoliation in the Pacific Northwest, however, it causes little defoliation in the Southwest.

Similar Insects and Diseases:  The pine butterfly adult resembles the common cabbage butterfly. In addition, the young larvae feeding in groups may be confused with other gregariously feeding larvae such as sawflies. These would include Neodiprion spp. and Zadiprion spp. of sawflies. Pandora moth is also a defoliator of ponderosa pine. This insect has a 2-year life cycle. Mature larvae are distinctly larger, brown to yellowish green in color and possess stout, branched spines on each body segment.

References:  23