If a branch on your pine or a rose bush in your yard is suddenly covered with small larvae that look like caterpillars, you may be dealing with sawflies. Around your Union home, sawflies can strip a shrub surprisingly fast, and they're one of the easiest garden pests to get wrong. They look like caterpillars but aren't, and that difference changes what works against them. Below, we'll cover what sawflies are, how to recognize them, whether they're harmful and why a professional opinion is worth it before you spray anything. If you're not sure what's on your plants, our pest inspection services can help you find out.
What Sawflies Are
Sawflies are insects in the same broad group as wasps, bees and ants. The name comes from the female's saw-like egg-laying tool, which she uses to cut slits in leaves or needles. The adults look like small, thick-waisted wasps or flies. They don't sting and rarely get noticed.
The larvae are the part you'll see. They feed on leaves or needles, often in tight groups, and they look so much like caterpillars that most people assume that's what they are. Different sawflies prefer different plants, and several are frequent in home landscapes:
- Pine sawflies. Groups of larvae that feed on pine needles, often on mugo, Scots and other pines.
- Roseslugs. Small, slimy-looking green larvae that skeletonize rose leaves.
- Other species. Sawflies also feed on dogwood, birch, willow and many other trees and shrubs.
How To Tell A Sawfly Larva From A Caterpillar
From a distance, they're nearly identical. Up close, a few details help:
- Prolegs. Caterpillars have five or fewer pairs of fleshy legs on the rear part of the body. Sawfly larvae usually have six or more pairs.
- Head. Sawfly larvae often have a large, round head with a single small eye spot on each side.
- Group behavior. Many sawfly larvae feed side by side and rear up together in an S or question-mark shape when disturbed.
- Slug-like look. Some, like roseslugs, look more like tiny slugs than caterpillars.
Why Identification Matters
This is the main reason to call the pros. Bt, a common treatment sold for caterpillars, is a natural bacterium that works only when caterpillars eat it. It doesn't work on sawfly larvae. Homeowners who assume they have caterpillars can spend weeks spraying the wrong product while a shrub loses its leaves.
Sawflies also have their own timing. Some feed in spring, some in summer, and a few have more than one generation a year. Knowing which one you have tells you when to look and how long the problem is likely to last. It also tells you whether you need to act at all. Some feeding ends on its own within a few weeks, and a healthy plant will push out new growth. Other species keep coming back every year to the same shrub until something changes.
Are Sawflies Harmful?
To people and pets, no. They don't bite or sting, and they don't come inside your home. To plants, it depends on the species and how much they eat:
- Some pine sawflies eat only older needles, so the tree keeps its new growth and usually recovers.
- Others eat new growth too, which can thin or even kill small trees and shrubs if it happens year after year.
- Roseslugs mostly cause cosmetic damage, leaving leaves see-through and brown.
The damage often looks worse than it is, but a young or stressed plant can have a hard time recovering from repeat feeding.
What You Can Do Right Now
- Look closely. Count the prolegs and note the plant, the color of the larvae and whether they feed in groups.
- Take photos. Get close-ups of the larvae and the damage.
- Remove small groups by hand. On low shrubs, you can wear gloves and knock larvae into a bucket of soapy water, or prune off the branch tip they're feeding on.
- Check again in a few days. Eggs may hatch in waves, so new larvae can show up after the first group is gone.
- Keep plants healthy. Water during dry spells so plants can push out new growth after feeding.
When To Call A Professional
Call for help when you can't tell what the larvae are, when they're on a large tree you can't reach or when the same plants are stripped year after year. For treatment on trees, a certified arborist is the right choice, and EcoFusion doesn't spray or inject trees. What we can do is inspect your property, confirm whether you're seeing sawflies, caterpillars or something else and recommend the right next step. Our NJ DEP-licensed technicians use Integrated Pest Management, and if the insects are getting into your home, we use EPA-registered, eco-safe products to handle that part of the problem.
Sawflies are easy to mistake and simple to manage once you know what they are. A quick, accurate identification is the best way to protect the pines, roses and shrubs around your Union home.