Forest Insect Defoliators
Pine Sawflies
Neodiprion spp., Zadiprion spp.

Hosts:  Ponderosa pine, piñon

Figure 27. Figure 27. Adult female pine sawfly (Neodiprion spp.) oviposting on ponderosa pine.

Symptoms/Signs:  Pine sawfly larval appearance varies by species and by larval instar, but most are green or yellowish green in color with black, tan or orange head capsules. Larvae are found in either spring-summer or fall-winter feeding gregariously on older foliage, consuming only the outer needle tissue while leaving the central ribs intact. The central ribs later turn yellow brown and break off. Later instar larvae feed singly and consume most of the needle. Eggs are laid in slits cut in the edge of living pine needles. A papery cocoon covers the pupae. Adults are broad waist wasps. Infested trees have sparse foliage and thin crowns.

Figure 28. Figure 28. Needle with row type egg cluster and newly hatched pine sawflies on ponderosa pine.

Effects:  Eight species of sawflies infest pines in the Southwest, five of those are found on ponderosa pine. Different species have different preferences for the size of host attacked, and location on the host where they feed. Pine sawflies in the Southwest typically attack open-grown trees or areas where pine is growing at a low density. The same trees are frequently defoliated year after year. In general, defoliation causes slower growth. Repeated defoliation can result in top-kill and tree mortality.

Similar Insects and Diseases:  See pandora moth and pine butterfly.

References:  12, 19, 24, 64, 67, 69

Figure 29. Figure 29. Late instar of Neodiprion gilletei feeding on ponderosa pine.
Figure 30. Figure 30. Zadiprion rohewri larvae on pi˜on pine. Note the regurgitated resin droplets that are sued as a defense mechanism against attacking predators and parasitoids.
Figure 31. Figure 31. Late instar larva of Zadiprion townsendii feeding on ponderosa pine.
Figure 32. Figure 32. Pine sawfly defoliation of ponderosa pine needles showing both early and late instar feeding.