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How to identify it
- Full-grown larvae are about an inch long (Alabama reports up to about 1.25 inches) with a dark, chocolate-brown head and a dull green body marked with a heavy black stripe along each side, often with two lighter stripes below the heavy ones. Newly hatched larvae have shiny black heads and gray-green bodies. In a Texas outbreak the striped greenish larvae had head capsules ranging from orange to black.[1][3][4]
- Like other sawflies, the larvae have six or more pairs of fleshy prolegs on the abdomen and a dark eye spot on each side of the head, whereas moth and butterfly caterpillars have five or fewer pairs of prolegs.[4]
- Young larvae feed in groups, often five or six tiny black-headed larvae ringing a single needle. They girdle the needle by eating its soft outer tissue, so the rest of the needle turns reddish brown, and twigs full of these dead needles, called flags, show up from the ground or from low-flying aircraft. Older larvae feed singly or in pairs but still move from branch to branch in groups and eat whole needles down to short stubs or to the fascicle.[1][4]
- The adult female is about three quarters of an inch long with four wings, an orange and black body and thread-like antennae; the male is about a quarter inch, entirely black, with feathery antennae. Cocoons are mahogany-colored, capsule-like and spun in the topsoil or litter.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Redheaded pine sawfly | Also attacks Alabama pines in colonies. The loblolly pine sawfly's mature larva has a dark chocolate-brown head and heavy black side stripes rather than rows of spots, and it feeds in early spring on medium and large forest trees.[1][3][2] |
| Blackheaded pine sawfly | Another southern Neodiprion that attacks Alabama pines. The loblolly pine sawfly's older larvae have dark brown heads (only the newly hatched larvae are black-headed), hatch from March to mid-April, and have a single generation a year.[1][3][2] |
| Pine sawflies | Several Neodiprion species feed on southern pines. The loblolly pine sawfly is the one that defoliates stands of loblolly and shortleaf pine in the South-central states in early spring, with eggs that overwinter in the needles and adults that fly in October and November.[1] |
Where it lives
First observed in southern Arkansas in 1940, it has been found in eastern Oklahoma, southeastern Texas, southeastern Missouri, northern Arkansas, central Louisiana and northern Mississippi, with periodic large outbreaks in Arkansas. It also attacks pines in Alabama, where a 2014 outbreak hit five northwestern counties, and has caused outbreaks in counties east of Dallas, Texas.[1][2][3][4]
Biology and life cycle
The chief host in Texas, Arkansas and Louisiana is loblolly pine; shortleaf pine is seldom more than lightly infested there even when mixed with badly defoliated loblolly, though elsewhere the two pines and occasionally longleaf are attacked indiscriminately. Medium and large forest trees are preferred, with open-grown saplings attacked occasionally.[1]
There is one generation a year, and the egg is the overwintering stage. Eggs hatch from early March to mid-April depending on local weather, and the larvae finish feeding in 30 to 40 days, mainly in April and May.[1][3]
Mature larvae drop to the ground and spin cocoons in the topsoil or litter. Most pupate and emerge as adults in October and November, but a small share stay in the cocoon as long as two autumns. Females mate and begin laying soon after emerging, sawing 1 to 20 pockets in each of several needles, one whitish-yellow egg per slit spaced about a body length apart, and laying 90 to 120 eggs, often all in the needles of one twig.[1]
A polyhedral virus sometimes destroys many larvae, sustained cold and rain in spring leave larvae inactive so that many starve or sicken, rodents dig up cocoons, and more than 20 parasite species attack it, the most important probably a parasitic fly and an ichneumon wasp. Birds take few larvae and no egg parasites are known.[1]
Damage and signs
- In heavily infested stands trees can be completely defoliated in early spring before the new shoots and needles develop. New foliage restores a nearly normal appearance within a few months, and no trees are known to have died from this sawfly's defoliation alone.[1][3]
- The real loss is growth: diameter growth may be reduced by 50 percent or more for several years after a single heavy defoliation. Alabama notes that repeated attacks over two or more years may cause mortality but that growth loss is the main damage.[1][2]
- On shortleaf pine the larvae occasionally eat the terminal buds and tender bark of new growth as well as old needles. Outbreaks are sporadic and localized, driven by favorable weather and the state of the natural enemies.[1][3]
Health risk
The sources mention no effect on people or pets; the larvae are plant feeders and the adults are small, seldom-seen wasps.[1][2]
Control
Prevention
In forests, chemical control is usually neither recommended nor necessary. Outbreaks are sporadic, most pines recover and flush new needles by summer, and weather, predators, parasites, viruses and starvation generally knock the population down by the following year. The Alabama Forestry Commission's advice for a stand under attack is to wait and see whether the pines rebound.[2][3]
Traps and physical control
On ornamental pines the clustered larvae can be hand-picked, or the tree can be sprayed.[2]
Pesticides
Insecticides are generally reserved for infested pines in residential or commercial settings, since treating large acreage is cost-prohibitive, and in forests are considered only if the population has not fallen by the second year. Where a stand is sprayed, the Forest Service advises applying as soon as possible after egg hatch in early spring, by air for medium and large forest trees; its 1970 product list is out of date, so check current registrations with extension or the state forestry agency.[3][2][1]
Common questions
- My mature loblolly pines were stripped in April. Will they die?
- Probably not. No trees are known to have died from loblolly pine sawfly defoliation alone, and most grow a new set of needles by summer. The cost is slower growth, which can be cut by half or more for several years after a heavy defoliation.[1][3]
- How do I tell these from caterpillars?
- Sawfly larvae have six or more pairs of fleshy legs on the abdomen and a single dark eye spot on each side of the head; true caterpillars have five or fewer pairs. Loblolly pine sawfly larvae are dull green with heavy black side stripes and a dark brown head, feeding in groups on old needles in spring.[4][1]
- Is there a second generation in summer?
- No. This species has one generation a year: eggs overwinter in the needles, larvae feed from March into May, and the adults do not emerge from their soil cocoons until October and November.[1][3]
Sources
- USDA Forest Service, “Neodiprion taedae linearis: A Sawfly Pest of Loblolly and Shortleaf Pines, Forest Pest Leaflet 34 (J.F. Coyne, revised 1970).” www.fs.usda.gov/foresthealth/docs/fidls/FIDL-34-SawflyofPines.pdf (accessed 2026-11-10)
- Alabama Forestry Commission, “Pine Sawfly (forest insects page).” www.forestry.alabama.gov/Pages/Informational/Insects/Pine_Sawfly.aspx (accessed 2026-11-10)
- Alabama Forestry Commission, “Sawfly Spells Trouble for Pine Trees in Northwest Alabama (press release, 28 May 2014).” media.alabama.gov/pr/pr.aspx?id=8785&t=1 (accessed 2026-11-10)
- Texas A&M AgriLife Extension, “Sawfly alert, Insects in the City (27 April 2011).” citybugs.tamu.edu/2011/04/27/sawfly-alert/ (accessed 2026-11-10)
- iNaturalist, “Neodiprion taedae taxon page (order and family).” www.inaturalist.org/taxa/890771 (accessed 2026-11-10)