Sawflies

Hibiscus sawflies, adult (left) and larvae (right). Photo: John Olive, Auburn University, Bugwood.org

Updated: May 9, 2023

Sawfly insects chew leaves

Sawflies look like caterpillars but they are a different type of insect. Sawflies are related to bees, wasps, and ants (in the order Hymenoptera). They go through four stages in their life cycle – egg, larva, pupa, and adult. The larvae look similar to caterpillars or, in some cases, tiny worms. Sawfly larvae have more than 5 pairs of prolegs on their abdomen, which helps to distinguish them from caterpillars.

Sawflies often have shiny red or blackheads and the bodies often have black spots or stripes. They are usually 1 to 2 inches long. They like to feed in groups and many may be found together on a branch. Damage may appear as small chewed spots on leaves to complete defoliation of individual branches or shoots. In Maryland gardens, sawflies are most often seen chewing on roses, hibiscus, dogwood, columbine, birch, and pine. There are multiple species that affect different plants.

Management of sawflies

In general, sawflies are best controlled when they are young larvae. Monitor your plants regularly for symptoms of chewing damage. You can simply pick off sawfly larvae by hand and drop them into a container of soapy water to kill them. A forceful spray of water can knock small sawflies off of a plant; the dislodged insects cannot climb back onto the plant. Heavy infestations of young larvae also may be sprayed with horticultural oil or spinosad.

Remember: Even though sawflies look like caterpillars, they are not. A biological pesticide used to control caterpillars, Bacillus thuringiensis (Bt), will not control sawflies since they are a different type of insect.

Common types of sawflies in Maryland

Roseslug Sawfly

The roseslug sawfly is one of three common sawflies that attack roses (others are curled and bristly roseslugs).
Mature larvae look like caterpillars, about 1/2" long and yellow-green with yellow heads.
The larvae skeletonize the leaves and in heavy infestations can cause leaves to turn brown and curl.
Check roses in May and June (in Maryland) for the slug-like, greenish-yellow larvae on the undersurface of skeletonized leaves. Roseslugs can be active through the fall.

Bristly roseslug larvae are about 5/8" long and greenish-white with long, stout bristles. They skeletonize leaves by feeding from the undersides of the leaves and later chew holes through the leaves.

Curled roseslug larvae are metallic green above, marked with white dots, grayish white underneath, with yellow-brown heads. They curl up like a cutworm and are about 3/4" when mature. Curled roseslugs initially feed by skeletonizing the leaves, but eventually, defoliate entire leaflets except for the largest veins.

More about Rose Sawfly

Dogwood Sawfly

black and yellow larva is a dogwood pest — Dogwood sawfly

The dogwood sawfly is an occasional pest of dogwoods. They are mostly seen on shrub dogwoods - e.g., silky dogwood (Cornus amomum) and red osier dogwood (C. sericea).
There is one generation each year. Monitor for them starting in early July.
Upon hatching, the young larvae feed together and chew the leaves.
After the second molt, the larvae become covered with a white powdery material.
After their final molt, they lose the powdery covering and change color. The mature larvae are yellowish with a shiny black head and black spots.
These mature larvae will wander about in search of an overwintering site, generally in soft or decaying wood.

More about Dogwood Sawfly

Hibiscus Sawfly

chewed leaves of a hibiscus plant from sawfly insects — Hibiscus sawflies, adult (left) and larvae (right). Photo: John Olive, Auburn University, Bugwood.org

Hibiscus sawfly larvae feed on hibiscus, rose of Sharon, hollyhock, and mallow.
As they get larger, all leaf tissue except the veins is consumed, which gives the leaf a lacy appearance.
The adults are small (3/16 inch), black fly-like insects.
The pale green worms have black heads and tiny black spines on each body segment.
They are slightly gregarious with up to three larvae feeding on one leaf.
Monitor plants for damage in June, July, and August. Hibiscus sawfly has multiple generations per season.

More about Hibiscus Sawfly

Redheaded Pine Sawfly

caterpillars - actually sawflies - with green and black spot on pine - they are redheaded pine sawflies — Redheaded Pine Sawfly. Photo: Herbert A. 'Joe' Pase III, Texas A&M Forest Service, Bugwood.org

Redheaded pine sawfly prefers to feed on jack, red, shortleaf, loblolly, slash, longleaf, pitch, Swiss mountain, and mugo pines. It may occasionally attack white pine and other conifers.
The mature larvae are 1 inch long, have reddish heads, and a yellowish-white body with 6 rows of irregular black spots.
There are two generations per year and prepupae overwinter in the soil.
Large infestations may defoliate and kill small pines.
There are approximately 10 other species of sawflies that attack pines in Maryland, including European pine sawfly, Blackheaded pine sawfly, and White pine sawfly. Their appearance will vary somewhat, but their behavior and control are the same as the Redheaded pine sawfly.
Stressed trees are most often attacked.

More about Redheaded Pine Sawfly

Columbine Sawfly

Note: Other University Extension websites may include information about pesticides that are not available, not legal to use, or not recommended in Maryland. Pesticides are hazardous and may harm organisms that are not the target pest. If you choose to use a pesticide, read and follow the directions and safety precautions on the label.