Sawfly – All You Need To Know

Despite belonging to the same order as bees, sawflies are far from beneficial. Instead, sawflies are pests that can potentially cause a lot of damage depending on the species. 

There are 7,000 species of sawflies, with a variety of hosts. This article seeks to shed light on these pests and explore effective treatment methods.

sawfly
Elm Sawfly

What Are Sawflies?

They are a group of insects characterized by a saw-like ovipositor, which explains the name. The 7,000 different species are spread across seven different families, which makes the sawflies a very diverse bunch. 

However, all these families belong to the vast superfamily Tenthredinoidea

Sawflies are often easy to mistake for bees, wasps, and hornets and belong to the same order as the – order Hymenoptera. 

They are also referred to as “primitive wasps.” Both adult and larval sawflies are pests, though the extent of damage varies from one species to another.

Types of sawflies

1.     Elm Sawfly

The elm sawfly stands out, especially because its larva is one of the largest sawfly caterpillars in North America. 

If you find a metallic blue fly-like bug with a striped abdomen, it might be an elm sawfly. 

These insects are notorious for defoliating elm and willow trees, though they sometimes infest boxelder, apple, birch, maple, and other tree species. 

Female elm sawflies use their saw-like ovipositors to cut open the leaves of host plants and lay eggs.

2.     Rose sawfly

If you find sawfly larvae on roses, it’s likely the larvae of rose sawflies. Also known as the rose slug sawfly, the adult looks like a black fly with a yellow abdomen. 

It’s mostly their larvae that cause damage, feeding on the soft tissues of rose shrub leaves and exposing the hard tissues inside. 

This skeletonization process badly affects the aesthetic value of the rose shrubs by causing the leaves to turn brown and dry.

sawfly
Elm Sawfly

3.     Pine sawfly

There are several species of pine sawflies out there, among which the European pine sawfly is the most abundant species in North America. 

Adult pine sawflies have black heads and bodies and are dotted with yellow and white spots. 

Some species of pine sawflies give birth to several generations per year, and their larvae are particularly devastating. 

Although they mostly defoliate the crown and the upper part of trees, a pine sawfly infestation can sometimes result in complete defoliation too. 

Defoliation caused after the formation of the winter buds can result in the death of branches or even the whole tree.

4.     Dogwood sawfly

A black fly with a yellow abdomen, dogwood sawflies closely resemble wasps. As their name suggests, dogwood plants are their most preferred host species. 

The adults usually emerge around May to July. Female dogwood flies use their ovipositor to insert up to 100 eggs in a leaf, usually lining them across entire leaves along the veins. 

Leaves with dogwood sawfly eggs are easy to identify, as each egg causes a tiny brown bump to appear. 

Their larvae can be a huge problem because matured caterpillars of this species tend to bore into softwood, including various lawn furniture. 

Interestingly, the larvae of dogwood sawfly take up several appearances, colors, and textures during the molting stages.

sawfly
Dogwood Sawflies

5.     Birch sawfly

Growing up to almost an inch in length, these large sawflies lay their eggs under the bark of birch trees. 

Once again, the saw-shaped ovipositor turns out to be handy. As with all the other pests of this species, the larvae feed on their host plants. 

Thankfully, birch sawflies or their larvae don’t cause a lot of damage or defoliation on birch trees. 

The effects are usually only short-lasting, though young birch plants are more vulnerable to damage.

6.     Raspberry sawfly

The raspberry sawfly is an agricultural pest notorious for feeding on raspberry, loganberry, gooseberry, and blackberry. 

Raspberry plants are their most common hosts but can usually survive sawfly infestations without much issue. 

In most cases, raspberry sawflies only cause small holes in the leaves. Heavy infestations, however, can result in the leaves getting completely skeletonized. 

Adult raspberry sawflies look like stout black wasps, while the larvae are a light green shade,  very similar to the leaves they infest.

Elm Sawfly

Where Do They Live?

Sawflies are very common in the US, and you can find them in every state. 

Besides other North American countries like Canada and Mexico, these pests are also abundant in Japan and Europe. 

Sawflies mostly reside in the temperate zones in the Northern hemisphere. 

While one can still find some species of sawflies in African forests, they’re scarce in Australia and absent in New Zealand. 

As for their preferred habitat, most of them have specific host plant species. As you may have noticed already, the sawfly species are usually named after the plants they prefer to feed on.

What Do They Eat?

Adult sawflies usually feed on pollen and nectar from flowers, but leaves are often a part of their diet too. Besides, they’re also insect predators and may prey on ants. 

It’s the larvae of sawflies that cause the most damage due to their feeding habit. These caterpillars feed on plant tissue, which is why they cause extensive damage to leaves. 

Besides, they also have strong mouthparts that allow them to pierce the bark tunnels and suck out tree sap. 

Although most sawflies have specific host plants, some are relatively more generalist and cause a lot of damage to garden plants.

sawfly
Bottlebrush Sawfly

What is the Lifecycle of sawflies?

Most species of sawflies have a very short lifespan and die within about six months of hatching. They spend most of this time as larvae and get to spend only a week or two as adults. 

However, many sawfly species in Minnesota live up to a year. They have four distinct life stages, like most members of the insect world.

Egg

Their eggs are inserted into plant leaves and petioles and show up as yellow and brown spots on the surface. 

As they develop, they grow in size and often protrude through the surface. 

Depending on the weather and the species, the time taken for them to hatch ranges from two to eight weeks.

Larvae

The larvae of sawflies are commonly grouped as caterpillars due to the similarities in their appearance and behavior. 

Sawfly larvae usually have black spots all over them and move around in groups. When disturbed, all of them tend to rear back their heads together. 

This is a key identifying characteristic that can help you distinguish sawfly larvae from other caterpillars. 

The larval stage lasts two to four months and comprises six instars. 

You might not notice them until they’ve reached the final instar. This is when they start eating large chunks of leaf tissue.

sawfly
Sawfly Larva

Pupae

While some species of sawfly larvae pupate in the soil, others spin cocoons attached to host plant leaves. 

Sawflies take longer to pupate than most common insect species, and this stage may last a few months.

Adults

Finally, the adults emerge and live for up to a couple of weeks. Some sawfly species have longer lifespans and can live for more than a year.

Where Do They Lay Eggs?

Adult female sawflies usually use their ovipositors to insert eggs in plant leaves and petioles. 

The eggs may be laid singly, along leaf veins, or in clusters of 30 to 90 eggs, known as pods or rafts. 

Some species of sawflies glue their eggs to the surface rather than inserting them into the plant tissue.

Do They Bite or Sting?

Sawflies don’t usually pose a direct threat to humans as they cannot bite or sting. 

Despite their similarity to wasps, they do not have stingers, and their saw-like ovipositors aren’t as good weapons. 

For this reason, they’re also commonly known as “stingless wasps.”

sawfly
Elm Sawfly

Are They Poisonous or Venomous?

Sawfly larvae can secrete a distasteful and irritating liquid in self-defense to ward off predators. 

If you end up agitating them or making them feel threatened, they might squirt it on your skin or, worse, into your eyes.

Are They Harmful to Humans as Pests?

While not every sawfly species are equally harmful, many of them are major. Sawfly larvae can cause extensive damage to host plants by defoliating them and skeletonizing the leaves. 

Heavy sawfly infestations can also result in the death of the host plant or tree. 

Thankfully, there’s only one type of sawfly known to attack vegetable crops, and it only feeds on sweet potatoes.

Can They Come Inside Homes?

Sawflies don’t usually get indoors, and most of their preferred hosts aren’t houseplants. However, they might get in through open windows or doors. 

Especially if there are trees around your home, there’s a chance that sawflies or sawfly larvae infesting them might fall inside.

Elm Sawfly

What Are sawflies Attracted To?

Naturally, sawflies are primarily attracted to their preferred host plants. While Both trees and shrubs are vulnerable to various sawfly species. 

If you have any potential host plants in your garden, you should watch out for sawflies in spring.

How To Get Rid of sawflies?

Healthy and mature deciduous plants can usually survive sawfly infestations for a season.

Even if they get defoliated during a severe infestation, they can regrow the leaves.

However, even if a sawfly infestation doesn’t cause any lasting damage to your garden, sawfly damage can greatly lower the aesthetic appeal.

Effective ways to get rid of sawflies include:

Manual removal

If there’s just a small number of sawflies, you can remove them manually and kill them by putting them in a bucket of soapy water.

Spraying water

Simply spraying the infested plants with a high-pressure jet of water to knock off the pests should work too. However, take care not to damage delicate plants.

Natural predators

Attracting natural predators to your garden is a great way to keep pest populations under control. Parasitic wasps can help you get rid of sawfly larvae.

sawfly
Elm Sawfly

Low-impact insecticides

Before using chemical insecticides, try out low-impact options. Horticultural oils and insecticidal soaps are effective against young larvae and have minimal impact on beneficial species.

You may also use Spinosad and Azadirachtin for residual treatment.

Chemical insecticides

If the other methods fail to bear fruit or you need quick results, you may have to resort to chemical insecticides. 

A single treatment of contact residual insecticides like bifenthrin, permethrin, or carbaryl is usually enough. 

Alternatively, you may use systematic insecticides that transport through the plant tissues and kill larvae feeding on the leaves or cones.  

Frequently Asked Questions

Can sawflies hurt you?

When threatened or aggravated, sawflies secrete an irritable liquid during the larval stage. Apart from this, they aren’t capable of hurting you. 
Sawflies can’t bite humans, and unlike wasps, they lack stingers. As long as you don’t mishandle sawfly larvae, you usually need not worry about getting hurt.

Should I get rid of sawfly?

While sawflies are pests, you don’t always need to get rid of them. As long as your plants remain healthy and strong, they can usually withstand and survive sawflies. 
However, if it’s a large infestation or the sawfly species is known to cause heavy damage, you should work on eliminating them. 

What do sawfly larvae grow into?

Sawfly larvae grow into adult sawflies – insects belonging to the same order as wasps, ants, and bees. While some sawflies look like flies, many species closely resemble wasps. 
You are more likely to come across sawfly larvae than adult sawflies, as they live for a very short period as adults.

Is a sawfly a wasp?

Although sawflies are often mistaken as wasps or known as stingless wasps, they’re a completely different group of insects. 
Unlike wasps, sawflies don’t have stingers – they have a saw-like ovipositor instead that they use to insert eggs into plant tissue.

Wrap Up

Sawfly identification can be a little difficult due to the similarities they share with other insects. Many sawfly species are Batesian mimics and replicate the behavior of wasps to avoid predators. 

However, it’s the larvae that you need to get rid of, and hopefully, this article has been helpful in this regard.

Leave a Comment