How to kill sawfly?

Sawfly Insect Control: How To Get Rid Of Sawflies

Sawflies get their name from the saw-like appendage at the tip of their body. Female sawflies use their “saw” to insert eggs into leaves. They are more closely related to wasps than flies, though they don’t sting. Sightings of adult sawflies are rare, but you may occasionally see them near flowers and flower buds where their offspring cause damage to the foliage. Keep reading for more sawfly information.

Sawfly Information

There are several types of sawflies, and most are named for the type of plant on which they feed. Here are a few types that you may find in your landscape:

  • Currant sawfly larvae have green or tan spots, and they strip the foliage off of currant plants.
  • There are a number of different conifer sawflies that can seriously injure their chosen species by feeding on needles and tunneling into buds and shoots.
  • Pear and cherry sawfly larvae skeletonize the leaves of their chosen species.
  • Pecan sawflies leave holes of different sizes in pecan tree leaves.
  • Willow leaf sawfly damage is easily recognized by the fleshy galls that develop at the spot where the female injects her eggs into the leaves.

Sawfly Damage

Sawfly damage is caused by the larvae that feed on plants in several different ways, depending on the species. Some leave holes or notches in leaves, while others skeletonize the leaves by completely devouring the tissue between the veins. They may roll up the leaves or spin webs. A few species leave galls on the foliage.

A light infestation may cause only a little cosmetic damage that is easily removed through pruning, while a large number of sawflies can seriously damage or even kill a tree.

How to Get Rid of Sawflies

The control of sawflies is directed at the feeding larvae. Each species of sawfly has its own distinct appearance and habit, and they change their appearance as they develop. Although a few species of sawfly have larvae that resemble slugs, most look like caterpillars. It’s important to learn the difference between sawfly larvae and caterpillars because the insecticides used to kill caterpillars have no effect on sawfly larvae.

The easiest way to tell the difference between sawfly larvae and caterpillars is to look at the legs. Sawfly larvae have three pairs of true legs, followed by seven or eight pairs of fleshy, false legs. Caterpillars have five or fewer pairs of false legs that are armed with tiny hooks.

Handpicking may be the only control measure you need to control light infestations. Sawflies have several natural enemies that keep them in check, including predatory beetles, parasitic wasps, and viral and fungal diseases. Avoid using broad spectrum insecticides that will damage the beneficial insect population. Good choices that are effective, but have little environmental impact, include insecticidal soaps and narrow-range oils.

Another aspect of sawfly insect control is directed at the pupa that overwinter in cocoons in the soil. Cultivating the soil exposes them to freezing weather and birds that feed on them. Cultivate the soil several times over the winter months, taking care not to damage the roots of dormant plants.

In the summer, our yards are abuzz with insects belonging to the order Hymenoptera: bees, wasps, ants, and sawflies (also called wood wasps). The third largest order of insects, scientists believe that hymenopterans evolved from sawfly-like insects that first appeared more than 200 million years ago during the Triassic Period. Hymenoptera (hi-men-OP-terr-uh) is from the Greek humen for membrane and pteron for wing, which describes two of the common features of these insects.

How they benefit us

Bees pollinate our plants and produce honey for backyard beekeepers. Wasps pollinate, as well as prey on numerous pest insects. Ants clean up organic debris, turn our soil and feed on pests, such as slugs, aphids, and spider mites. The tunneling habit of ants is said to aerate the soil as much as earthworms do.

On a broader scale, bees contribute billions of dollars annually to the U.S. Gross Domestic Product through crop pollination and production of honey and beeswax. Parasitic wasps are valuable to farmers, many of whom buy them from commercial insectaries for biological pest control. And, the insects themselves are an essential food source for other animals.

Hymenopterans are found everywhere in the world, except for colder altitudes and the Polar Regions (an exception is the very hardy bumblebee species, Bombus polaris, that ranges even into the Arctic.)

The number of Hymenoptera species in the world varies, depending on the source. According to BugGuide.net, a community of professional and amateur entomologists, there are more than 153,000 species. The Smithsonian Institution and the Encyclopedia Britannica estimate about 115,000. Other sources range as low as 100,000. Most sources agree, however, that 17,000 to 18,000 species are inhabitants of the U.S.

Common characteristics

  • Two pairs of membranous (thin, often see-through) wings, although some species have wings only during mating flights (for example, ants) or lack wings altogether. Wings have minimal veining, and the forewings are larger than the hindwings.
  • The forewings and hindwings lock together with tiny hooks. In smaller species, this can give the impression of being just a single pair.
  • Compound eyes, usually large. A few ant and wasp species are blind.
  • Chewing mouthparts, although some have a modified lower lip that forms a tongue.
  • Females usually have an ovipositor (egg-laying organ) that’s modified to either saw, pierce or sting.
  • Life cycle: complete metamorphosis, which is a progression from an egg to a larva and then to a pupa from which they emerge as an adult.

Hymenoptera’s two suborders

Hymenoptera is split into two suborders: Apocrita and Symphyta.

Those aren’t headphones on this Long-horned Bee, Anthophora montana. They’re her compound eyes. (Amber Reese, USGS Bee Inventory and Monitoring Lab; cc by 2.0)



Apocrita (uh-PAH-cree-tuh) contains bees, wasps, and ants. This group can be easily identified because they have an abdominal constriction that separates the abdomen from the thorax and looks like a “waist.” Many also have a stinger.

Notice this wasp’s skinny “waist.” (Magnus Johansson / Flickr; cc by 2.0)



Symphyta (sim-FI-tuh), the other suborder, consists of sawflies. Sawflies are related to wasps, but resemble flies because they lack the familiar, thin wasp “waist.” “Saw” comes from the females’ saw-like ovipositor, which they use to slit openings into plants where they lay their eggs.

Sawfly. Notice the thick “waist.” (Gail Hampshire / Flickr; cc by 2.0)



Almost all sawflies possess two “knobs” on their thorax called cenchri (sing.: cenchrus) — these hook to the underside of the wings and keep them in place while the insect is resting. Most sawflies lack a stinger

Social structure

Most hymenopterans are solitary and live alone — mud dauber wasps, potter wasps, and mason bees are some examples. But there are others that are social, meaning they live in colonies — well-known examples are honeybees and bumblebees, as well as yellow jacket and paper wasps. All ants are social.

Bees

Look closely, and you’ll see there are many kinds of bees in your yard, not just honeybees and bumblebees. There are also sweat bees, carpenter bees, mason bees and others. All bee species have hair somewhere on their body. Their hair can help you distinguish bees from wasps, which are mostly hairless.

The hair is important because it traps pollen as bees move from flower to flower sipping nectar. The pollen gets rubbed off and pollinates many flowers as they go. Bees value pollen as food and fly it back to their hives. Beforehand, they moisten and stick it to a flat area on their back legs called a pollen basket. The “basket” doesn’t exist in a way we think of one; it’s a surface surrounded by hairs that help hold the ball of pollen in place. The ball grows larger and larger as they add to it.

This Honeybee, Apis mellifera, has pollen clinging to her body. The solid yellow oval on her leg is a packed pollen basket. (Ivar Leidus / Wiki; cc by-sa 4.



In the winter, depending on the species, bee queens hibernate alone, and their colonies die off or, like honeybees, entire colonies stay alive in their hives. Those don’t hibernate and may even venture out on warm winter days.

Male bees don’t sting. The all-female worker bees can sting, but they’re not aggressive unless they think they’re under attack. When working in your garden, move about calmly, and they’ll just go about their business as you go about your own. Sometimes side-by-side. If you’re wearing a color they think might be a nectar source, they may check you out; don’t swat at them and they’ll soon move away. All about honeybees

All bees (except cuckoo bees) build nests. Nests are located in a variety of places. Some species, such as mason bees, nest in holes. Carpenter bees drill nesting holes in wood. Others, like miner bees, dig holes in the ground. Honeybee hives may be found in trees, tree hollows or even walls and attics. Bumblebees may build their nests in such places as existing, abandoned holes underground, under sheds or loose siding, in woodpiles or in birdhouses.

Bee distribution

There are 4,000 native bee species in North America. The southwestern U.S. and northern Mexico are home to the largest variety of bees in the world. There are 1,000 to 1,200 species of bees “within a one hundred mile radius of Tucson,” according to the Carol Hayden Bee Research Center in Tucson. Around the world, about 25,000 species have been described so far. Of these, there are seven species and 44 subspecies of honeybees.

The smallest bees in the world belong to the genus Perdita. Native to the U.S. and Mexico, there are about 700 species and subspecies of them ranging in size from 0.08 to 0.39 inch (2.0 mm to 10.0 mm). Wallace’s Giant Bee, Megachile pluto, an Indonesian species, is considered to be the largest bee species in the world. The female has a body length up to 1.5 inches (38 mm) and a wingspan of 2.5 inches (63.5 mm).

In the U.S., the smallest bee is Perdita minima, the size of a gnat. The largest bees are carpenter bees which measure from 0.75 to 1.0 inch (1.9 to 2.54 cm) in length.

Wasps

Distinguish wasps from bees by their hairless (or mostly so) body and skinny “waist.” The waist, technically called a petiole, is a somewhat cylindrical body segment (sometimes two segments) that fits between the thorax and the abdomen.

A Pompilid wasp from India, showing its skinny “waist,” a distinguishing feature of all wasps. (L. Shyamal Wiki cc by 2.5)



Wasps are omnivorous. As adults, most wasps feed on nectar, but their young are carnivores and fed insects and spiders. Some wasps are parasitic and lay their eggs in the bodies of live prey. According to National Geographic, nearly every pest insect in the world is preyed on by wasps, which makes them valuable animals to patrol a garden.

Some wasps are social; they have nests and a caste system. Paper wasps (family Vespidae) are an example. A fertilized queen constructs a nest containing a few cells, lays a few eggs in them and raises those offspring, which are sterile.

A paper wasp queen guards her nest. The cells contain her first offspring at various stages of development. (Yogendra Joshi Wiki cc by 2.0)



Once they’re adults, the offspring take over the care of the queen and the hive. The queen’s job is to lay eggs. The hive gradually gets bigger as the family grows larger.

Wasps nest in a variety of places. For example, yellow jackets commonly nest in the ground, but sometimes in wall voids and attics. Hornets build nests in bushes, on tree branches or sometimes the sides of buildings, in attics and walls. Paper wasp nests are constructed in trees, under the eaves of houses, in attics and other structures.

Distribution of wasps

There are more than 100,000 species of wasps around the world. All but about 1,000 species are solitary. The males of a parasitic Costa Rican species, Dicopomorpha echmepterygis, are the smallest adult insects in the world. Wingless and blind, they measure no more than 0.005-inch (0.139 mm) in body length. The female, which has wings, is only a smidgen larger. At the other extreme is an Asian species, the Asian Giant Hornet, Vespa mandarinia, which has a body length up to 1.75 inches (45 mm) and a wingspan of 3 inches (7.6 cm). In North America, wasps range in size from minuscule to about 1.25 inches (0.2 to 30 mm) long.

Ants

Ants seem to be everywhere, don’t they? They live in colonies in many places: underground, in wood, in trees, in mounds, in spaces under flowerpots and inside unused garden hoses. And, of course, kitchens, if they can get away with it!

Their colonies are headed by a queen or queens, which usually have wings. The ants we see out foraging for food are all-female worker ants, which lack wings. Colonies can be very long-lived, and queens can live up to 30 years.

When a colony splits up (swarms), a different group of ants is produced — both males and females, they have wings and fly away from the old colony to begin new ones. (Andy Reago & Chrissy McClarren / Flickr; cc by 2.0)



Most ants are omnivores with a varied diet that includes small insects, spiders, dead animals, fungi, seeds, and grains. They like sugary foods, too. Carpenter ants, for instance, are particularly fond of a sweet liquid called honeydew that’s produced by aphids and scale insects. Ants like people food, a lot — syrup, jelly, honey, bananas and other fruits, but also vegetables, bread, chips and other foods that people eat. Pet food, too.

Despite their name, carpenter ants don’t eat wood. They feed on meats and sweets. If they come indoors, they feed on honey, jelly, other sweets, and pet food. (Richard Bartz / Wiki; cc by-sa 2.5)



Depending on the source, there are an estimated 10,000 to 12,500 species of ants around the world, with thousands more awaiting classification. Somewhere between 580 and 1,000 species inhabit North America. Most ants range in length from 0.07 to 0.4 (0.2 to 10 mm) inch. The smallest ants in the world are believed to be in the genus Carebara. Carebara atoma, for example, is only about .039 inches (1 mm) long. The largest ant in the world may be the female Dinoponera gigantea, which is 1.2 to 1.6 inches (3 to 4 cm) long. The largest ants in North America are probably Black Carpenter ants — workers are about 1/2 inch (1.27 cm) long, and the queens are about 1 inch (2.54 cm) long.

Sawflies

Sawflies are wasps that don’t have a thin petiole (waist) between their abdomen and thorax. This difference makes many of them resemble flies. The “saw” in their name comes from the female’s saw-like ovipositor. Another distinction, with a few exceptions, is that their larvae look like butterfly or moth caterpillars, while bee, wasp and ant larvae are grub-like.

Sawflies are wasps that don’t have a thin petiole. (Gail Hampshire / Flickr; cc by 2.0)

Sawfly females use their ovipositor to cut into plants, including trees. They deposit their eggs in the holes, and the hatched caterpillars of most species feed on the leaves, usually in groups. A few species feed on plant stems. Adults are carnivorous, but some species also feed on nectar and pollen. Sawflies don’t sting.

There are about 9,600 sawfly species in the world, with the majority in North America and Eurasia. The smallest adult sawflies are about 0.19 inch (3mm) long. Most species are in the 0.20 to 0.79 inch (5 to 20mm) range.

*Images in composite photo at top of page, left to right: European Honeybee (Apis mellifera) by Esteban Armijo / Flickr; cc by 2.0; Figwort Sawfly (Tenthredo scrophulariae) by Nigel Jones / Flickr; cc by 2.0; Black Carpenter Ant (Camponotus pennsylvanicus) by Welcome Wildlife; Birch Sawfly (Cimbex femoratus) by Aleksey Gnilenkov / Wiki cc by 2.0

More reading:
Insects in your yard: mayflies
Explore an insect-friendly yard
Why you should create a backyard wildlife habitat

In the Garden: Where are all these wasps coming from?

We can loosely divide wasps into three groups: nonstinging, solitary nesters, and the social nesters. Examples of nonstinging wasps are sawflies and insect parasites. Solitary nesting wasps will sting only if handled. Social nesting wasps will sting when the nest or individual feels threatened. While some social nesting wasps can be considered beneficial helping control pest insects, the aggressive nature of social wasps often makes them intolerable.

Paper wasps are slender and narrow-waisted with long legs, three-quarters to one inch long and reddish-orange to dark brown or black. They often have yellow body markings. Nests are paper-like, shaped like tiny umbrellas, and found under eaves, in attics, or in home porches.

There are several species of yellow jackets common to New England and they are the most troublesome wasps. Yellow Jackets may form nests in walls, under mulch, underground, or occasionally in trees and shrubs. Gardeners often mistakenly call them bees because they are black in color with yellow markings. Some attack live prey (earwigs, caterpillars, etc.), some just scavenge, and some do both.

The white-faced or baldfaced hornet isn’t a true hornet. It is actually a type of yellow jacket wasp. The baldfaced hornet is up to three-quarters of an inch long, and blackish with white markings, especially on the front of the head. Hornets construct an inverted, pear-shaped, gray-brownish paper-like nest that can be up to three feet tall with the entrance at the bottom.

Each wasp nest starts new in the spring and is enlarged as the colony builds up to hundreds of individuals. The nest is largest in the autumn and not reused the following year. Mated queens overwinter away from the nest in protected outside locations or in structures. A queen killed in the fall or early spring will eliminate an entire nest.

Preventing a problem with wasps is the best control measure. Sanitation is important; remove garbage frequently and keep tight lids on all trash receptacles. Pick up and dispose of over-ripe fruit and vegetables in the garden. Should a wasp fly near you, slowly raise your arms to protect your face and move slowly indoors or through bushes to escape. Rapid movement and striking at a wasp often provoke attacks.

If a wasp gets into the automobile while you are driving, never panic. The wasp wants out of the car as much as you want the wasp out. Slowly pull over and open car windows and doors.

To control an established nest in a wall or in the open, find the nest entrance from a safe distance. The entrance of an aerial nest is usually near the bottom. After dark or before sunrise, spray into the nest entrance with a wasp and hornet aerosol. Never stand directly below a nest when treating as dying wasps may fall from the nest.

Wasps are normally in the nest at night and can’t fly without light. If you use a flashlight, a red lens or red cellophane cover will prevent wasps from detecting it (insects don’t “see” red light). Otherwise, be prepared to switch it off if wasps begin to leave the nest.

It is particularly safest during cool, wet weather, such as after a rain storm. Observe the nest for a day or two for further activity. If you see no live wasps, seal the entrance. Never seal the entrance before all the wasps are dead. If wasps are still active, re-treat with the aerosol.

Wall nests are sometimes found some distance from where the wasps are seen entering, which make aerosols ineffective. Dusts are recommended if the aerosol fails after two applications.

For ground nests, dusts or liquids are most effective, and you should seal the entrance with moist soil after treating. Other types of wasps will build nests in cavities in the ground, in hollow logs or under stones. Often, you can quickly destroy offending nests effectively by simply pouring a kettle of boiling water over them after dark.

Control individual wasps found indoors with a fly swatter or flying insect aerosol. Don’t handle stunned or dead wasps with bare hands as you may expose the wasp stinger.

You should remember that wasps aren’t just a nuisance, they can be very valuable as they feed on caterpillars, mosquitoes, and flies. Try to imagine the fly problem we could have without the parasitizing activity of wasps.

Jeremy Delisle is program coordinator for the UNH Cooperative Extension Education Center. The center answers questions about gardening and more at [email protected], or call (877) 398-4769 between 9 a.m. and 2 p.m. Monday through Friday.

Sawfly Larvae Control & Facts

Adult sawflies have four wings, so they are not true flies. They measure up to 1/2″ in length. Larvae resemble caterpillars, although they have some “false legs.”

Most sawflies seem to prefer older foliage. Larvae devour the needles of conifer trees. Tree branches may appear defoliated.

So… What’s a Conifer Sawfly?

Adult sawflies have four wings, so they are not true flies. They measure up to 1/2″ in length.

Larvae resemble caterpillars, although they have some “false legs.”

Larvae may have a grayish body with lighter striping or they may have a yellowish or whitish body with dark spots along the length of its body.

Reproduction Patterns of Conifer Sawflies

Conifer sawfly eggs spend the winter inside gaps in pine tree branches. When they hatch in the early part of spring, the larvae begin to feed voraciously on the needles of the pine trees.

They then pupate in plant debris on the ground, maturing into adults by fall. The female adults will lay eggs which will then hatch in the spring.

Some sawflies lay eggs in the spring that will hatch into larvae which then pupate, spending the winter in cocoons.

Conifer Sawfly’s Habitat

Conifer sawflies dwell in the eastern regions of the United States and Canada. As the name implies, these pests prefer pine trees and can be particularly devastating to forest areas.

Symptoms of Conifer Sawfly Damage

Most sawflies seem to prefer older foliage. Larvae devour the needles of conifer trees. Tree branches may appear defoliated.

Results of Conifer Sawfly Infestation

If there is a large infestation, and repeated feedings continue, a branch or an entire tree may end up being defoliated and die. If it does not die, it may end up being more susceptible to secondary diseases.

At the very least, growth of the tree may be affected if an infestation occurs.

Conifer Sawfly Controls

What?

The combination of Insecticidal Soap and Botanical Pyrethrins will kill Sawfly Larvae on contact if they are spotted in your trees. Azadirachtin is also an effective control for Sawfly Larvae.

How?

Insecticidal Soap (Potassium Salts of Fatty Acids) & Pyrethrin – The soap will penetrate the insect’s shell and kill it by dehydration. Adding Pyrethrin creates the organic equivalent of a one-two knockdown punch. Pyrethrin is a nerve agent that will absorb into the insect and kill by paralysis.

Keep in mind, this soap is not like dish detergent, it’s a base from a blend of plant sources and pyrethrin oils and come from the chrysanthemum flower.

Azadirachtin – A derivative of the Neem Tree, Azadirachtin is an insect growth regulator (IGR). It disrupts and speeds up the molting process of larval insects. It kills the insects when they try to molt to the next phase of life too soon. This control also repels the adult sawfly and many other insects.

Safer® Brand offers a variety of sawfly larvae control products to help control and eliminate this garden pest and revive your plants. Please check out our sawfly larvae control products for more details about how they work and how, when, where they should be applied.

Carefully read and follow all instructions on the product packaging for safe and effective results. It is recommended with any pesticide to test plants for sensitivity to the product. Spray a small section of the plant in an inconspicuous area and wait 24 hours before full coverage.

When?

Since these formulas are contact killers and they do not persist in the environment, several applications may be needed for full control. As a general rule, much like watering, do not use these products in the peak of the day or when temperatures exceed 90 degrees F to avoid wilting or browning of the leaves.

Why Choose a Pest Solution?

Thankfully, many people are starting to realize that products that are compliant for use in organic production are the best solutions available. Why exactly are these products preferred? These solutions break down quickly into their natural elements. They are preferable to chemical pesticides that leave residuals where they are sprayed, causing long-term detrimental effects on the environment.

Plus, if you’re using the wrong insect-control products on produce, these chemicals can make their way into your food, eventually reaching your home and family. You put your love and sweat into your garden because you want to put great food on the tables of your family and whoever else eats your produce. So you want to choose a product that befits the fruits of your labor.

Natural Predators

Natural enemies of the conifer sawfly include parasitic insects, especially parasitic wasps. These insects are great partners in helping to control sawfly infestations in your organic garden.

Parasitic insects, including parasitic wasps, lay their eggs inside the sawfly’s body eventually killing the host insect. Lure parasitic insects to your garden by planting nectar or pollen producing plants.

To aid the organic gardener, parasitic wasps and other parasitic insects can be purchased through a commercial insect breeder. Make sure if you purchase these insects you have an actual garden insect infestation or you may notice parasitic wasps migrating to your neighbor’s yard in search of food.

In the spring, parasitic insects may lay their eggs in the larvae of the conifer sawfly.

Plant nectar or pollen producing plants according to your local greenhouse or garden center’s suggestion.

Environmental Controls

Collecting and destroying larvae and knocking them off trees will help control these pests. These methods should be used in combination with other control methods such as natural and organic controls.

Lay sheets on the ground around the pine trees to catch larvae that fall, then gather and destroy the larvae. Remove larvae by hand picking when the infestations are small.

When larvae are spotted, these environmental control measures should be taken. Delaying the use of control measures may allow populations to rise and damage to increase.

Safer® Brand leads the alternative lawn and garden products industry, offering many solutions that are compliant with organic gardening standards. Safer® Brand recognizes this growing demand by consumers and offers a wide variety of products for lawns, gardens, landscapes, flowers, houseplants, insects and more!

If the leaves of your rose have ugly little brown window-pain-like spots, or are getting holes in them, the culprit causing the damage is most likely rose sawfly larvae. Look under the leaves and you might spot the troublemakers at work.

The larvae are caterpillarlike insects with yellowish-green, almost see-through bodies and dark green heads. Although the larvae may have completed their life cycle and therefore are not present when you look for them, keep an eye out for their return.

There can be up to six generations a year. Whenever you spot them, either blast the larvae off with a powerful spray from a hose nozzle, or use the ‘el kabotski’ technique by using your fingers to turn them into sawfly marmalade.

Keep your bearded iris blooming

Bearded iris are popular for their big, colorful flowers that are often pleasantly fragrant. Although they’re relatively easy to care for, they tend to stop blooming if the roots become crowded.

To keep them flowering at their best, divide them at least every five years or sooner if blooming becomes sparse. The best time to divide them is between mid-July and the end of August.

Begin by cutting the leaves to one-third their length. Then dig the clump and wash the soil off with a hose. Cut the rhizomes apart keeping only those with a healthy fan of leaves and firm white roots. Allow the rhizomes to cure for a couple of days in a dry shady location before transplanting.

The rhizomes grow in the direction of the fan at the end of the rhizome, so when you replant, place the rhizomes about a foot apart with the leaves aiming outward.

Before planting, work plenty of compost and about a half-cup of organic flower food into the planting area. Replant with the top surface of the rhizome level with the soil surface. If you bury the rhizome too deeply, your iris may not bloom.

Try a beautiful way

to repel flies

A caller on my gardening show once asked me how to keep flies out of her house. Other than window screens, I lacked a good solution. The next caller was from Austria and offered a suggestion. She told me that Austrians don’t plant Pelargoniums (zonal and other types of geraniums) in their window boxes just for aesthetics. Their real purpose is to repel flies.

Although I was somewhat dubious, I had the perfect place to test her claim. The day we moved into our house, we discovered that we had a problem with flies that constantly flew in circles between the house and detached garage. Nothing we tried would make them go away, and their presence embarrassed the living tweetle out of us whenever we had visitors.

I planted up a container with Pelargoniums where the flies hovered. To my great surprise the flies instantly disappeared, and the only time they ever came back was one year when I purposely didn’t plant any.

If you’ve got a fly problem, give Pelargoniums a try. I think that any kind from Martha Washington to ivy geranium will do, and even if it doesn’t work, maybe visitors will notice the attractive flowers rather than the embarrassing flies.

Ciscoe Morris: [email protected] “Gardening with Ciscoe” airs at 10 a.m. Saturdays on KING-TV.

by P.J. Liesch and Susan Mahr, University of Wisconsin – Madison

An adult columbine sawfly.

Sawflies are a group (sub-order Symphta) of insects in the same order as the bees, ants and wasps (Hymenoptera) that feed on plants. These insects can be distinguished from most other hymenopterans by their broad waist, unlike the narrow connection between the thorax and abdomen of a wasp, and by their caterpillar-like larvae. The sawflies get their common name from the saw-like appearance of the ovipositor, which females use to cut slits in stems or leaves to lay their eggs. This is a very primitive group – dating back 250 million years ago to the Triassic – and the majority (true sawflies, the Tenthredinoidea) are all herbivores, feeding on the foliage of many different plants, although one group (Orussoidea) are external parasites of wood boring beetles. There about 25 families*, with most of the 8,000 species worldwide in the family Tenthredinidae (about 5,500). The rest of this article is about the phytophagous true sawflies.

*If you’re interested in taxonomy, the families are arranged into 7 superfamilies:

Tenthredinoidea, with 6 families (Argidae, Blasticotomidae, Cimbicidae, Diprionidae, Pergidae, Tenthredinidae) and about 7,000 species
Siricoidea, 2 families (Anaxyelidae, Siricidae)
Pamphilioidea 2 families (Megalodontesidae, Pamphiliidae)
Cephoidea, 1 family
Xiphidrioidea, 1 family
Xyeloidea, 1 family
Orussoidea, 1 family

The adults of sawflies tend to be inconspicuous, and look somewhat like wasps, but do not sting. They feed on pollen and nectar, so may be seen on flowers as well as their larval host plants. They are not very active, making only short flights in sunny weather, and resting on leaves otherwise. Many sawfly species are parthenogenetic; since they do not need to mate to reproduce, males are very rare even in species where males are known to occur.

Adult elm sawfly.

The adults are short-lived, usually only a few days to a week, just long enough to develop and lay eggs. The female sawfly uses its ovipositor to cut into young adult leaves, petioles or stems to deposit her eggs scattered across the leaf surface, along the edge of the leaf, or on a leaf vein, singly or in groups of 30-90 called “rafts” or “pods”. Leaf-mining species typically lay only one egg per leaf. The eggs may be inserted into the plant tissue or glued to the surface. As the eggs develop, they often expand in size so that they may end up partially projecting from the leaf surface even if they were laid within the leaf.

The eggs of European pine sawfly are inserted into the needles, where they appear as evenly spaced yellow or light brown spots.

Larva of Monostegia abdominalis.

The eggs hatch in 2-8 weeks (depending on the species and weather) into leaf-feeding larvae which look and often act very similar to caterpillars (the larvae of insects in the family Lepidoptera). Both sawfly larvae and caterpillars have three pairs of thoracic legs, but differ in that caterpillars have 2-4 pairs of prolegs (fleshy, leg-like projections) on the abdomen while sawflies have 6 or more.

Melaleuca sawfly larvae. USDA photo K7873-3

Other differences that are a bit harder to see are that caterpillars have crochets (tiny velco-like hooks) on the prolegs while sawfly larvae do not and caterpillars have 4-6 eyes on each side of the head while sawfly larvae have just a single pair of tiny eyes. A helpful identifying feature out in the field is that many sawflies are gregarious (i.e., live together in groups) and will rear back in unison when disturbed.

Azalea sawfly on leaf and damage.

The larvae feed and develop through 6 instars before reaching maturity. This may take 2-4 months, but often are not noticed until the last and largest instar when they are consuming large amounts of leaf tissue.

A cocoon of columbine sawfly.

Once they have completed their larval development they either leave the host plant to pupate in the soil or spin a cocoon attached to a leaf, depending on the species. The adults emerge in a few to several months, depending on the species. Most sawfly species have a single generation per year, but some may take two years to produce one generation.

Unlike many other insects which disperse as soon as they hatch, sawflies often stay together to feed in groups and therefore can quickly defoliate portions of their host plant. Some species line up next to each other with all the heads at the leaf edge as they chew away the blade. They may all rear up together or tap their abdomens up and down when disturbed. Larvae of the spitfire sawfly regurgitate a distasteful irritating liquid when bothered to deter predators such as ants. A few species are leafminers, feeding internally on leaf tissue between the upper and lower leaf surfaces. Some tropical species form large congregations on tree trunks or the ground during the day, dispersing at night to feed.

Sawfly larvae are fed upon by many animals, including some birds, lizards, frogs, ants, predatory wasps and other insects, while carnivorous mammals such as shrews and deer mice and several species of beetle larvae prey on the pupae.

Hollyhock sawflies defoliating a hollyhock leaf.

When numerous, plant-feeding sawflies can cause substantial damage in forests and landscapes. Large trees are rarely seriously injured and normally put out another flush of leaves if heavily damaged. Young trees that are completely defoliated completely may be stunted or killed. Predators and parasitoids regulate sawfly populations in natural habitats. In the landscape larvae can be removed from trees and killed by squishing or dropping them into boiling water, although this is not practical on a large scale. Small trees can be sprayed with a number of chemicals, if mechanical removal is not effective. Although sawflies may look like caterpillars or slugs, since they are not, it makes a difference in what chemical are effective against them – for example, BT or Bacillus thurningiensis only works against true caterpillars and is ineffective on sawfly larvae – so be sure to read the label before using any insecticide. Insecticidal soaps, neem oil, and many synthetic insecticides can be used to control sawflies. Apply insecticides only when larvae are actually present.

A colony of European pine sawfly.

There are many different species of sawflies, each of which feeds on specific plants or groups of related plants. The common name of the sawfly usually includes its host. In Wisconsin the most commonly encountered sawflies include:

European pine sawfly, Neodiprion sertifer, is found on various pines, especially mugo, Scot’s, red and jack pine. The striped, gray-green larvae with a black head and legs grow up to an inch long, feeding in groups only on the previous season’s needles. They will strip one branch before moving to another, and will even leave a tree in search of others if all the old needles are eaten. Since the new growth is never eaten, European pine sawfly seldom kills trees, but repeated defoliation slows growth and ruins the appearance of trees. This species overwinters as eggs laid in the needles, with larvae emerging in mid-May. Adults emerge in the fall to lay eggs on the current season’s growth near the ends of the branches.

Roseslug adult.

Roseslug larva.

Roseslug sawfly, Endelomyia aethiops, is a Eurasian species only found on roses. The light green larvae with orange heads grow to about ½ inch long as they feed on the upper leaf surface from mid-May through June, leaving only the leaf veins. They secrete a slimy substance over their body surface that makes them resemble small slugs. They overwinter as prepupae in the soil. The adults emerge in spring to lay eggs in the leaves. There is one generation per year.

Bristly roseslug larva.

In addition to this species, there are two other sawflies that can be found on roses in Wisconsin. The bristly roseslug sawfly, Cladius difformis, has bristle-like hairs covering the body and can produce two to six generations per year. The curled roseslug sawfly, Allantus cinctus, curls up the body when at rest and generally has two generations per year.

Slimy black, slug-like pear sawfly and damage.

Pear sawfly (pear slug), Caliroa cerasi, is another Eurasian species which is fairly common on pear and apple trees, but can also occur on plum, cherry, cotoneaster and hawthorn. The shiny olive-green larvae are slimy and slug-like, up to 1/2″ long when full grown. They begin appearing in early June and feed for about a month on the upper leaf surfaces, leaving only the leaf veins, before dropping to the soil to pupate. Heavily defoliated trees appear scorched and leaves may drop prematurely. A second generation can begin in early August.

Birch leafminer mine.

Birch leafminer, Fenusa pusilla, is a European species common on European, white, gray and paper birches, but yellow and river birch can also be affected. The small, flattened white larvae form small, blistered translucent spots on new leaves as they feed between the upper and lower surfaces. Those spots turn brown and papery and the leaves eventually drop off. Most people don’t realize the brownish patches on leaves are even caused by an insect, let alone a sawfly. This is usually just a minor cosmetic issue. Once the larvae complete their development they drop to the ground to pupate in the soil, going through 3-4 generations annually.

Elm sawfly larvae.

Elm Sawfly, Cimbex americana, is a native species which feeds preferentially on elm and willow, but sometimes attacks maple, cottonwood, poplar, birch and other trees. This is one of the largest species of sawfly in North America with full-grown larvae ranging from 1½-2 inches long. The white, light gray, yellow or light green (and occasionally pink) larvae with a rough, pebbly texture have a black stripe running down the top of the body with a row of black dots (spiracles) on each side. They often curl up into a circle when not feeding on the leaves. Usually defoliation is localized to a single tree or group of trees and since but they are feeding late in the season this rarely causes serious damage to the trees. They drop from the tree to overwinter and pupate in the soil. There is only one generation each year. The robust adults are more distinctive than most sawfly adults. They are up to an inch long, black with yellow bands on the abdomen of the females, while males have a distinct white spot just behind the wings and the rest of abdomen is reddish-brown.

Dogwood sawfly larva.

Dogwood Sawfly, Macremphytus tarsatus, is another native species which feeds on a variety of ornamental and native dogwood trees and shrubs (Cornus spp.). The larvae, which feed on the leaves through the summer, are black, with yellow bars across the back and solid yellow underneath, but often appear white because of a powdery white waxy coating that covers them except during the last instar and following each molt. They can cause quite noticeable defoliation of dogwood shrubs but don’t kill the plants. The larvae drop to the ground to overwinter in cocoons made of rotted wood. If the appropriate material is not found on the ground they can invade wood fiberboard or siding of buildings, which may lead to woodpecker damage.

When columbine sawfl ies are numerous (L),
damage can be dramatic (R).

Columbine Sawfly, Pristiphora rufipes, is a European species which feeds on columbines. The small green larvae with dark heads eat the leaves, consuming everything but the midvein, as they grow up to about ½ inch long. They larvae drop off the leaves to pupate in brown, oblong cocoons amid leaf litter. There is only one generation a year in the upper Midwest. The damage can be quite noticeable the way that the stems get entirely clipped off, but plants usually recover, putting out a second flush of leaves.

Mountain ash sawfly, Pristiphora geniculata, is a European species found only on mountain ash and is the most common insect pest on this tree. The pale green-yellow larvae with black spots and a black or orange head grow up to ½ to ¾ inch long. The larvae feed in groups and eat entire leaves, leaving only the mid-veins, defoliating an entire branch before moving to another. They overwinter as prepupae in the soil, with adults emerging beginning in early June. Larvae of the first generation can be seen from mid-June through early August, while second generation larvae are usually found in late August or September.

Dusky birch sawfly larvae.

Dusky birch sawfly, Croesus latitarsus, is a native species only found on birch. The yellow-green with black heads and black blotches on their sides grow up to an inch long. They feed in groups around the edges of leaves. This species overwinters as prepupae in the soil, with adults emerging in spring to produce larvae which feed from May to early July. A second, overlapping generation may occur and feed through September.

Scarlet oak sawfly larvae.

Scarlet Oak Sawfly, Caliroa quercuscoccineae, is a native species which attacks several types of oaks but is most common on northern red oak and pin oak. The slimy-looking larvae feed in groups on the lower surface of the leaves, leaving only a fine network of veins which gives the leaf a transparent appearance. The damage (skeletonization) is not usually widespread but can be significant and quite noticeable on single trees but rarely affects tree health except on small, newly transplanted and stressed trees. Natural enemies usually keep the populations in check, but if not, the defoliation occurs late in the season so control is rarely necessary.

Pine catkin sawflies, Xyela spp., are odd sawflies and one of PJ’s favorites. The adults of these native species are tiny gnat-like creatures and are unlikely to be noticed. As the common name suggests, the larvae live in male pine catkins and drop from the catkins prior to pupation. At the right time, this can be very noticeable when tiny whitish larvae rain down from trees over decks/patios in spring. Naturalist Charley Eiseman has written about this interesting phenomenon on the BugTracks Blog at https://bugtracks.wordpress.com/2013/06/03/larvae-raining-from-pine-trees/.

White pine sawfly, Neodiprion pinetum, is a native species generally found on eastern white pine. The pale yellow larvae have four rows of black spots and black heads, growing to an inch long. The single annual generation feeds on both old and new needles from late June to early August. When the larvae reach maturity they drop to the ground and overwinter as prepupae in the soil. Adults lay eggs in the needles in the spring.


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How to Control Hymenoptera – Sawflies and Horntails

In the order Hymenoptera are sawflies and horntails (a type of wasp), which are pests that damage trees, shrubs, grasses (both residential and agricultural), raspberries and roses. The only exception are the sawflies in the family Orusidae, who themselves are parisitoids and attack wood borer beetles and horntails. These beneficials are found in many forested areas of California and help naturally control these pests.

Life Cycle
Female sawflies deposit their eggs in slits cut into the foliage of trees or shrubs, but a few attack grasses, raspberries and roses as sawflies can be plant specific. Once the larvae emerge, they begin to feed on the leaves, pollen and/or buds causing unsightly damage. The larvae look like large caterpillars with more than 5 pairs of legs and two eyes. They may be brightly marked with spots or stripes. Many of those that feed on conifers build webs or tents in which to feed. After feeding for three to four weeks, mature larvae spin a cocoon that turns brown and resembles a bud tip. Most fall to the ground. The adult sawfly will emerge from the pupal case, mate and start the life cycle again. Most sawflies have one generation a year; some have two.

Sawfly and Horntail Control

  • Prune damaged foliage and stems.
  • Parasitic wasps and predaceous beetles commonly kill sawfly populations. If damage is not severe, control measures may not be necessary.
  • Insecticidal soap or horticultural oil kill exposed sawfly larvae but may damage blossoms.
  • Neem Oils will stop eggs from hatching and larvae from developing if you spray neem directly on them. Neem oil acts as a contact insecticide, so residual impact is minimal after application, but avoid applying when pollinators or beneficial insects are present.
  • Spinosad sprays can be used as directed to control sawfly larvae.
  • Diatomaceous Earth can be used to help deter larvae from feeding.

Monitor adult sawfly and horntail populations with traps. Diligent monitoring will allow for earlier detection of pest populations and will suppress the number of new eggs being laid. View additional Borer Control Products.

Facts, Identificatio,n & Control

Scientific Name

Hymenoptera Symphyta

Appearance

What Do They Look Like?

  • Size: Sawfly adults are about 1/2 inch long.
  • Characteristics: Sawflies may look like flies, but are actually related to bees and wasps. The common name sawfly comes from their ovipositor, which is saw-like in shape and is used by the females to cut into the plants and lay eggs.
  • Body: They have four wings (flies have two,) and unlike many wasps, sawflies do not have the thin segment between the thorax and abdomen.

How Did I Get Sawflies?

Homes surrounded by trees and landscaping are prone to a sawfly infestation. The insects don’t normally enter houses, but larvae may fall into open doors and windows from branches close to buildings. Adults can also fly inside through the same openings. Sawflies are not actually flies, but are in the same insect group as bees, wasps, and ants.

How Serious Are Sawflies?

These pests aren’t an issue indoors, and unlike other wasps, females do not sting. However, infestations can affect outdoor trees. While they are usually benign, some species with large populations produce serious economic damage to large forests and cultivated plant acreages.

Larvae Damage

Larvae feeding habits can slow or stop plant growth, weaken leaves, and wilt stems. Both mature and larval sawflies are harmless to humans. Sawflies infest many species of trees and a large infestation may weaken a tree’s ability to withstand damage caused by other tree infesting insects.

How Do I Get Rid of Sawflies?

What You Can Do

Keeping your trees and plants healthy. Plants that are young and in poor health are likely to experience more injury and damage than healthy plants. If practical, you can also hand pick sawfly larvae from your plants.

Grown trees and shrubs can withstand moderate sawfly defoliation without experiencing reduced growth or mortality. This is due to the abundance of predators such as wasps and beetles, plus the occurrence of fungal and viral diseases that often kill off sawfly populations. So, it is not wise to use conventional insecticides that will kill their predators.

What Orkin Does

If you need help with a sawfly infestation, seek the assistance of your pest management professional rather than relying on do-it-yourself procedures. Some other components of an effective sawfly management program include:

  • Inspection: Frequently inspect plants for sawfly damage. The earlier you find sawflies, the easier it will be to manage the population and prevent damage to your trees or shrubs.
  • Identification:Asking your pest management professional to identify any insect specimens to ensure that the correct control options are used. Your pest management professional can also advise you whether it is worthwhile to apply a conventional insecticide for sawfly control.

Your local Orkin technician is trained to help manage sawflies and similar pests. Since every building or home is different, your Orkin technician will design a unique program for your situation.

Orkin can provide the right solution to keep sawflies in their place…out of your home, or business.

Behavior, Diet, Habits

What Do They Eat?

Since there are so many different species of sawfly, their preferred host plants vary a great deal. Most coniferous feeding sawflies eat the tree’s needles and buds. Deciduous feeders will skeletonize, mine, or chew holes in the leaves. Sawflies feed on a wide variety of:

  • Coniferous & Deciduous Trees
  • Fruits
  • Nectar
  • Pollen
  • Wood

Larvae

The sawfly larval stages are plant feeders and look much like the caterpillar of butterflies and moths. Sawfly larvae will either feed inside or on the outside surface of plant leaves and stems or inside a gall that is produced when the female stings the plant leaf or stem. Sawflies usually have one generation per year and spend the winter months in the larval or pupal stages.

Sawfly Larvae

Q&A related to Sawfly Larvae

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by Bruce Wenning

Sawfly insects are in the order Hymenoptera that includes bees, ants, wasps, parasitic wasps, and sawflies. Metamorphosis is complete: egg, larva, pupa, adult (Borror, Triplehorn and Johnson, 1989). Sawfly larvae differ from larvae in the order Lepidoptera (butterflies and moths) by lacking noticeable body hairs, having a well-developed head, and possessing more than five pairs of abdominal prolegs that lack crochets. Crochets are characteristic in the Lepidoptera and are grasping, hook-like structures located on the bottom of the prolegs that serve in aiding larval locomotion and attachment to objects (Borror et al, 1989: Cranshaw, 2004).

Sawflies are plant feeders. Most are leaf feeders and some are actual pests of trees, shrubs, and garden ornamentals of various kinds. The roseslug sawfly (Endelomyia aethiops) is one of three rose attacking sawflies in the United States and is the subject of this fact sheet. The other two are the bristly roseslug (Cladius difformis), which produces five to six generations per year, and the curled rose sawfly (Allantus cinctus), which is the largest of the three and is a leaf skeletonizer as well as a cane borer producing only two generations per year (Johnson et al, 1989; Cranshaw, 2004). All three sawfly species feed on only roses (Rosa sp.) (Johnson and Lyon, 1991).

Figure 1. Leaf blotches during May and June are a telltale sign or symptom of the Roseslug Sawfly.

The family, Tenthredinidae has more of the commonly encountered sawflies in the landscape including the roseslug sawfly. It is a very large group of approximately 790 North American species (Borror et al, 1989). If you come in contact with a plant damaging sawfly, it most likely will be in this family.

The Roseslug Sawfly, Endelomyia aethiops

During the months of May and June in the Northeast you may have noticed leaf discoloration in the form of blotches on your rose leaves (Figure 1). If you inspect the leaves closely you will see the culprit! It is a small, narrow bodied larva called the roseslug sawfly, an introduced pest from Europe. The larvae have pale green colored bodies and light tan-orange colored heads (Figure 2).

Figure 2. Larvae has a pale green colored body and an orange-tan colored head. The larva feeds on the leaf underside. This photo shows the larva causing the characteristic windowpane damage as it feeds.

These sawflies cause leaf damage by feeding on the undersides of rose leaves causing a windowpane appearance, a form of leaf skeletonization (Cranshaw, 2004). In windowpane skeletonization, only one leaf surface is removed by feeding. Skeletonization can occur very quickly. I have observed this personally! In just one day, a large group of feeding larvae can cause extensive leaf damage (Ball and Ball, 1989). The adults do not cause this damage.

The adult sawfly (Figure 3) is about ¼ inch long and looks very wasp-like (Davidson and Raupp, 2010). In the spring, the female uses her saw-like or serrated ovipositor to cut into leaf tissue and deposit her eggs at the rose leaf edges. The ovipositor, located at the end of the abdomen, is the egg-laying apparatus which is part of the female’s reproductive system (Borror et al, 1989). Eggs hatch from the leaf edges from about mid-April to early May, and small first instar larvae emerge and chew leaf tissue between the leaf veins on the undersides of the leaves (Cranshaw, 2004; Sponable and Pellitteri, 2010). As larvae feed, they go through a few more instars (larval growth stages) causing significant leaf “windowpane” damage (Figure 4).

Figure 3. The adult roseslug sawfly is tiny (1/4 inch in length) and wasp-like in appearance.

When larvae are fully grown, about ½ inch long (final instar), they stop feeding, fall to the ground, and construct a cocoon or earthen cell for protection from the elements and predators. They remain inactive until the following spring when they will undergo pupation and turn into adult males and females. Adults will mate and the females will deposit their eggs into rose leaf edges from mid-April to early May, depending on temperature and weather conditions (Johnson and Lyon, 1991; Davidson and Raupp, 2010; Sponable and Pellitteri, 2010), and their life cycle will begin again. There is only one generation per year, which is why you only notice this species in May and June.

Figure 4. Windowpane damage up close caused by the feeding larva. Leaf tissue is consumed between the veins on only one leaf surface.

Rose plant damage is aesthetic and rarely kills the plant (Sponable and Pellitteri, 2010).

Organic Controls

Early detection is best. Start monitoring your roses by mid-April for first instar larvae infestation, abundance and distribution patterns. Hand-picking the larvae off the undersides of leaves and squishing them between your fingers or dropping them into a cup of rubbing alcohol works very well, but you must monitor your rose bushes daily to get them all or at least, most of them. Generally, the larvae are active for about one month or less depending on weather and temperature conditions.

Spraying the larvae with horticultural oil or insecticidal soap will kill the larvae. Complete larval coverage is necessary for effective kill. Horticultural oil (light weight) suffocates insect larvae, has a residual of a few days, and has very low mammalian toxicity (Ball and Ball, 1989). Insecticidal soaps are commercially formulated contact insecticides of low mammalian toxicity and designed to biodegrade in the environment within one to two weeks (Ball and Ball, 1989).

Using a garden hose to spray the larvae off the leaves with a strong water flow also works well. The larvae, once knocked off the host plant are incapable of climbing back up onto the leaves to resume feeding (Johnson and Lyon, 1991).

The insecticide Spinosad is absorbed into the leaf and disrupts the sawflies’ nervous system when the leaf is eaten by the larvae. It is considered safe, having a signal word – None (i.e. reduced-risk status) (Davidson and Raupp, 2010).

Follow label directions when using any of these low toxicity compounds.

Chemical Controls

Insecticides that contain the following compounds can be used when larval populations are high: acephate, azadirachtin, carbaryl, cyfluthrin, deltamethrin, diflubenzuron, lambda – cyhalothrin (Davidson and Raupp, 2010).

The new class of synthetic insecticides called neonicotinoids (imidacloprid, thiamethoxam, clothianidin, and dinotefuran) are used widely in landscape pest control; however, they should not be used because they kill pollinating insects (Black, Borders, Fallon, Lee-Mader and Shepherd, 2016).

Follow label directions when using any of these more toxic compounds.

Literature Cited

Ball, J and L. Ball. 1989. Rodale’s Landscape Problem Solver: A Plant-by-Plant Guide. Rodale Press, Emmaus, Pennsylvania. 439p.

Cranshaw, W. 2004. The Ultimate Guide to Backyard Bugs. Garden Insects of North America. Princeton University Press. 656p.

Johnson, W. T. and H. H. Lyon. 1991. Insects that feed on Trees and Shrubs. Cornell University Press, Ithaca, N.Y. 560p.

About the Author

Bruce Wenning has university degrees in plant pathology and entomology. He has been on the Board of Directors of the Ecological Landscape Alliance since 2003 and is the horticulturist at The Country Club, Brookline, Massachusetts where he battles this sawfly once a year at his workplace.

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