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. 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.
Figure 29. Late instar of Neodiprion gilletei feeding on ponderosa pine.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. Late instar larva of Zadiprion townsendii feeding on ponderosa pine.Figure 32. Pine sawfly defoliation of ponderosa pine needles showing both early and late instar feeding.