7/2/2013 - By Matthew Shultz

Sawflies are this month’s focus insect. Sawflies are in the order Hymenoptera, making them close relatives to ants, bees, and wasps. Adults only have one set of wings and often resemble a wasp when fully grown. This insect gets its name because most of the females in this family have a saw like appendage that they use to deposit eggs in leaf tissue.

The lifecycle begins in the pupae stage that can be found in the soil or decaying material. Depending on the species these adults hatch out of a pupae stage or cocoon in early to mid-summer. Some species of sawfly have one generation while others have multiple generations during a growing year. The adults mate and lay eggs on the underside of the host plant’s leaves. Most species of sawfly are host specific and only feed on one or two types of plants making them relatively easy to control in the nursery and greenhouse, of course growers who only produce a couple types of plants could find Sawflies devastating if left unchecked. Once the egg hatches the larvae undergo several larval instars as they grow in size and continue consuming more and more leaf tissue.

Dogwood Sawfly, note the yellow caterpillar is an earlier instar than the larger white larvae.
Photo by Matthew Shultz 

In the fall the larvae crawls down the plant and into the ground or decaying material where it will spend the winter in a pre-pupae stage awaiting spring. All sawfly larvae have chewing mouthparts. Some sawfly larvae like the Rose Sawfly only skeletonize a plants leaves. While other species will consume the entire leaf minus the mid-vein.

Bristly Rose Sawfly – This species of sawfly feeds on roses and late instar larvae eat holes in the leaves.
Photo by Matthew Shultz

Bristly Rose Sawfly – Early instar larvae of this species on skeletonize or window feed on rose foliage.
Photo by Matthew Shultz 

Sawfly Cocoon – Some sawfly species have multiple generations in a year, pictured here
is a sawfly that has just started to pupate.
Photo by Matthew Shultz

So how do you tell the difference between a caterpillar (moth or butterfly) and a sawfly?

Both resemble worm like pests that feed on a crop’s foliage. But the key is in the legs. Sawfly larvae always have a defined head capsule, it is easy to tell where the head stops and the abdomen begins. Sawfly larvae also always have 6 or more sets of prolegs. Caterpillars will always have less than 6 prolegs and their body can look as if it is part of the body. If you look at the picture below you can see 3 sets of legs towards the front of the head, these are true legs and both caterpillars and sawfly larvae will have them present. The legs you want to count are found up underneath the body and if this larvae were flipped over there would be 6 legs. You can also see a defined black head capsule on this Dogwood Sawfly.

Sawfly larvae – Green Arrow indicates where prolegs can be found;
6 or more and it is a sawfly.
Photo by Matthew Shultz

Controlling sawfly larvae is easily achieved using a preventative approach. Since most species hatch out during the summer months, spring applications of neonicotinoid products like Flagship and Tristar work very well. Apply these products in late April and early May to prevent these pests. Once these larvae are present and actively feeding products such as Conserve, Acephate, Pyrethroids and oils work well as long as uniform spray coverage is achieved.