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

Hosts:  Ponderosa pine, piñon

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 pupae. Adults are broad waist wasps. Infested trees have sparse foliage and thin crowns.

Figure 28. Row type egg mass of 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:  18, 23, 63, 65, 67, 68, 69

Note:  The taxonomy of this group has recently changed. The Neodiprion fulviceps Complex, described in Furniss and Carolin, has been split into N. fulviceps and a new species N. autumnalis. The life cycle information described for N. fulviceps in Furniss and Carolin is now considered that for N. autumnalis.

Figure 30. Late instar larva of Zadiprion rohweri feeding on piñon pine.Figure 31. Late instar larva of Zadiprion townsendii feeding on ponderosa pine.Figure 32. Defoliated ponderosa pine caused by pine sawflies near Flagstaff, Arizona.