European Pine Sawfly

European Pine Sawfly Larvae
Neodiprion sertifer

What they are not... Although these destructive larvae appear to be caterpillars, they are not; therefore, not controlled by the Bt (Bacillus thuringiensis) we normally reach for when halting such damage. Neither are they true flies. The adult phase are actually a type of non-stinging wasp. Why "sawfly?" The female uses her saw-like ovipositor to slit the pine needle edges, depositing one egg at a time.
What they are... Destructive, with voracious appetites! They fed in clusters of about 30 and when disturbed, they rear up, as one. It's as if the branch were alive and is most likely meant to frighten away predators (this has startled many humans, as well - myself included). Mid-May to early June is when we see typically find them feeding on Scotch, mugho, red, jack and most species of two-needled pines. (Occasionally feed on spruce, that may be adjacent to pines.) They are pests of the eastern and southern U.S. Once native to North America, they migrated to North Asia and Eurasia, via the Bering land bridge and somewhere around 1925 made their way back to New Jersey, then onto Ontario in 1939.
As larvae hatch, they immediately begin feeding on the needle which housed the egg. When this is gone, they move to adjacent needles. This explains their feeding on mature needles of the previous season, leaving the unfurled candles, or this year's new growth, uneaten (photo, above). Birds are nor serious predators - not serious enough to offer much control - evidently that scare tactic mentioned above, works pretty well! Parasitic wasps and naturally-occurring viruses provide some control in high density populations, in the wild.

The larvae go through 4 (for males) or 5 (for females) molts, before spinning cocoons on branches or in the leaf litter and fras, beneath the pine. Adults emerge in early fall, mate and lay eggs.

Control: Horticultural oils and insecticidal soaps are effective controls when larvae are 1/8-1/4" long. Pyrethrin or a pyrethrin/rotenone spray will prove effective in controlling older larvae. Imidacloprid (as in Bayer Advanced Tree & Shrub) is another control option. Spinosad and Neem Oil (K+Neem, etc.) are also effective. Pines under siege, quickly become thin and unsightly and are weakened by such attack. Control the pests now, feed the plants to increase vigor and look for the tiny hatchlings, as early as mid-April... after 2-3 years of vigilance and control (killing them before they can mature and lay eggs), you should get past the problem... just don't let your guard down - it always pays to be a vigilant gardener!


Photos: ©CBI 2008
©Deb Lambert 2008