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How to identify it
- Full-grown jack pine sawfly larvae average 2.2 cm (just under an inch) with a shiny black head and a yellowish-green body marked with three lengthwise stripes, the lowest sometimes broken into dashes. Florida describes the Virginia pine sawfly larva as black-headed and pale green with two black stripes and a row of black spots along each side.[1][2]
- The larvae feed gregariously in colonies of 50 or more from hatching until they drop to the ground, eating only last year's needles and, late in the feeding period, nibbling bark to leave cup-shaped notches on older branches.[1]
- Eggs are about 1 mm, ovoid and nearly white, three to six to a needle in slits sawed by the female, with 20 to 30 egg-bearing needles clustered at a shoot tip. The cocoon is a dark brown, papery, ovoid capsule about 1 cm long; the adult is a black and brown, fly-like insect about 1 cm long with four shiny wings.[1]
- Early feeding leaves reddish-brown, straw-like needle remains, and partly eaten branches take on a bottle-brush look. Disturbed larvae drop from the branch or bend into a U with head and tail raised and bring up a droplet from the mouth.[2][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Swaine jack pine sawfly | A different Neodiprion species of jack pine. The jack pine sawfly hatches in late April or early May from eggs that overwintered in the needles, finishes feeding by late June or early July, and has three stripes on a yellowish-green body under a shiny black head.[1] |
| Redheaded pine sawfly | The jack pine sawfly and Virginia pine sawfly have shiny black heads, not red ones, and their colonies strip only the previous year's needles.[1][2] |
| Red pine sawfly | Another Neodiprion of hard pines. Neodiprion pratti's northern subspecies damages jack pine on a large scale and takes red and Scots pine only occasionally, mainly when they grow among heavily infested jack pine.[1] |
| Pine sawflies | Among the Neodiprion species on pines, N. pratti is identified by its black head, three-striped yellow-green body (two stripes and side spots in the southern subspecies), spring feeding on old needles only, and bark notching late in the larval period.[1][2] |
Where it lives
The jack pine sawfly occurs in natural stands and plantations in Minnesota, Wisconsin and Michigan and across southern Canada from Manitoba to New Brunswick. The Virginia pine sawfly is native to Florida, where it feeds on loblolly and Choctawhatchee sand pine, and is listed among the pine sawflies of Alabama plantations.[1][2][3]
Biology and life cycle
Jack pine is the only host damaged on a large scale in the north; red and Scots pine are damaged occasionally, especially when growing with heavily infested jack pine. In the South the hosts are loblolly pine and sand pine, with Virginia pine among the pines attacked by Alabama's sawflies.[1][2][3]
There is one generation a year. The insect overwinters as an egg in a pocket sawed into a needle. Hatching begins in late April or early May depending on locality and climate, the larvae feed in colonies until late June or early July, then drop to the ground and spin cocoons in the duff or topsoil, where they rest as prepupae until about mid-August.[1]
Adults emerge in late August or early September and the females begin laying almost at once. Florida notes that Neodiprion larvae may stay in diapause in the cocoon for more than a year, and that colonies migrate from tree to tree when a host is stripped or crowded.[1][2]
Several species of parasitic wasps and flies are the most important natural enemies of the larvae, a virus disease causes epidemics, and bad weather, especially late spring frosts, cuts populations. Outbreaks of southern pine sawflies run in cycles, commonly 8 to 10 years apart.[1][2]
Damage and signs
- Trees of all sizes are attacked. Because only the previous year's needles are eaten, a heavily infested tree shows bare branches tipped with tufts of new needles; after two or more years of heavy feeding the old foliage can be gone entirely, and after several years the tufts sit on very short shoots.[1]
- Widespread mortality is rare because the new needles are almost full grown by the time feeding ends, but infestations lasting four or more years can kill trees. The more insidious loss is the gradual decline in growth and vigor, which is serious when other insects are feeding or growing conditions are poor.[1]
- In plantations the Alabama Forestry Commission notes that trees seldom succumb to pine sawfly attack; the damage is the tufted appearance, the partly eaten reddish needles and the visible colonies.[3]
Health risk
The sources mention no effect on people or pets; the larvae's oral droplet is aimed at insect parasites and predators.[2][1]
Control
Prevention
Direct control is usually unnecessary. Natural enemies generally bring the jack pine sawfly down before widespread damage, trees are seldom killed unless defoliated several years running, and Alabama likewise does not recommend treatment in plantations. Fully stocked stands that close canopy early are less at risk in the South.[1][3][2]
Pesticides
Where an infestation threatens the survival of trees, an insecticide may be necessary; insecticides can also be used on ornamental pines and Christmas tree plantations. The 1971 Forest Service leaflet had no registered product to name, so ask the county extension office or state forester what is currently labeled, and spray as little as possible to spare the natural enemies.[1][3][2]
Common questions
- Are the jack pine sawfly and the Virginia pine sawfly the same insect?
- They are two subspecies of Neodiprion pratti: banksianae on jack pine in the Lake States and Canada, and pratti on loblolly, sand and Virginia pine in the South. Both have black-headed, striped green larvae that feed in spring on old needles.[1][2][3]
- My jack pines have bare branches with green tips. Will they die?
- Usually not. The sawfly leaves the current year's needles, so the tree keeps growing, and natural enemies normally end outbreaks. Trees can die if heavy defoliation continues four or more years, and growth slows in the meantime.[1]
- When should I look for the larvae?
- From late April or early May, when the overwintered eggs hatch, until late June or early July, when the mature larvae drop to the ground to spin cocoons. Egg-bearing needles, with three to six eggs each in clusters of 20 to 30 needles at a shoot tip, can be found from early fall onward.[1]
Sources
- USDA Forest Service, “Jack-Pine Sawfly, Forest Pest Leaflet 17 (L.F. Wilson, revised November 1971).” www.fs.usda.gov/foresthealth/docs/fidls/FIDL-17-JackPineSawfly.pdf (accessed 2026-11-10)
- Florida Department of Agriculture and Consumer Services, Division of Plant Industry, “Pine Sawfly Larvae, Neodiprion spp., in Florida, Entomology Circular No. 258 (W.N. Dixon, January 1984).” ccmedia.fdacs.gov/content/download/4698/file/Pine_Sawfly.pdf (accessed 2026-11-10)
- Alabama Forestry Commission, “A Field Guide to Identifying the Most Common Forest Pests of Pine Plantations (pine sawflies entry).” forestry.alabama.gov/Pages/Informational/Images/Pine_Pest_Field_Guide.pdf (accessed 2026-11-10)
- iNaturalist, “Neodiprion pratti taxon page (order and family).” www.inaturalist.org/taxa/49455 (accessed 2026-11-10)