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Rose slug sawfly
Endelomyia aethiops

IDENTIFICATION — Smooth, translucent pale-green larvae could attack the leaves of your roses next May and June.

DAMAGE — Feeding on the surface of the foliage between the veins, larvae create a window-pane look. Leaves turn brown and curl. Large infestations may stunt the plant’s growth.

CONTROL — Prune out or handpick small populations. On cloudy days (so you don’t burn the leaves) in early summer, spray all plant surfaces with Safer^® insecticidal soap or horticultural oil to smother younger larvae. These controls don’t work as well on older larvae, but most of the damage has already been done by then.

If there are so many larvae that the plants stop growing and blooming, dust the affected plants with an insecticide containing carbaryl, such as Sevin^®. Or dilute and spray spinosad on all leaf surfaces in early summer. And all season, pick up debris and leaves from around plants to remove any larvae that may be hiding there.

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Pillbugs and sowbugs

IDENTIFICATION — Here are two bugs that look almost identical — pillbugs and sowbugs. The only difference seems to be that pillbugs roll into a ball when they’re frightened. Both go by many different names, such as roly-poly and wood lice. And they’re really not bugs at all — they’re crustaceans — they’re more closely related to crabs and lobsters. Adults can grow to 3/8 in. long.

DAMAGE — These bugs don’t really harm plants unless there are so many that the creatures need the food. Then they’ll feed on fine roots and stems of tender seedlings. Usually they’re scavengers, feeding on decaying plant material and hiding in dark, damp areas.

CONTROL — There’s no urgent need to control either one. But if you feel overrun, take away the critters’ hiding places. Remove dead plant material to the compost pile, get rid of boards and lift pots off the ground. These are some of their favorite spots.

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Flea beetle
Melittia cucurbitae

IDENTIFICATION — Young leaves of vegetables and flowers riddled with “shot” holes are a sign that flea beetles may be attacking your garden.

These small, black insects aren’t really fleas, but they jump like them. Although there are several species, damage and identification are the same.

DAMAGE — Adults chew round holes in the leaves, especially those of young plants, and on tender new growth. Foliage pierced with holes dries out quickly and dies. Flea beetle larvae sometimes feed on plant roots.

CONTROL — Adult flea beetles live over the winter in the soil and in debris. By cleaning up the garden in the fall, you’ll eliminate some of their hiding places.

Because they can produce a few generations each year, it’s important to get control of a population first thing in the spring. Protect young plants with spun-fabric row covers. Or, once you begin to notice damage, spray with neem oil or insecticidal soap every week or so.

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Squash vine borer
Melittia cucurbitae

IDENTIFICATION — There’s nothing worse than having your squash die on the vine because of squash vine borers. Adult moths are about 5⁄8 in. long with translucent wings. They have an orange and black striped body with fringed hind legs. Females emerge in spring to lay pinhead-sized eggs on the lower 3 to 4 ft. of squash vines.

Once the eggs hatch, the larvae bore into the stem and start eating. They grow up to an inch long with a white body and brown head. Larvae live and eat in the vine for four to six weeks, then move from the plant into the soil, where they spend the winter in a cocoon.

DAMAGE — Squash, zucchini, pumpkins and gourds are all susceptible to attack by these pests. Their favorite variety is Hubbard squash. Butternut squash, cucumbers and melons are less palatable but are sometimes affected. If the vines in your garden suddenly wilt, take a look at the base of the plant. Look for small holes in the vine, along with an accumulation of sawdustlike material. That’s frass, the debris larvae produce as they eat their way through the vine. As they eat, the larvae cut off water and nutrients, which kills the plant.

CONTROL — Because squash vine borer larvae are inside the vine, it’s difficult to get rid of them. But if you keep at it, you can minimize damage. In late spring, spray the vines weekly with an insecticidal soap to smother the eggs. Or spray the vine with Bt before the eggs hatch. This natural insecticide is safe to use on vegetables but needs to be eaten by the pest to be effective. In fall, destroy the vines as soon as possible after harvest to get rid of any remaining larvae. If you can till the soil to expose any cocoons to cold and predators, that will help, too.

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Emerald ash borer
Agrilus planipennis Fairmaire

IDENTIFICATION — If you have an ash tree (Fraxinus spp.), keep an eye out for emerald ash borer. Native to Asia, this pest is a serious problem in Michigan, Indiana, Ohio and Ontario. Several surrounding states have infestations to a lesser degree.

Emerald ash borers (EAB) are slender with metallic green wing covers. But you don’t have to see the insects to know that they’re there. Adults chew small, 1/8-in.-diameter D-shaped exit holes in the tree in spring. Soon after they emerge, females start laying eggs in the crevices of ash tree bark. Larvae burrow back into the bark to overwinter, pupating into adulthood in early spring.

DAMAGE — Adults feed on leaves and don’t do a lot of damage. It’s the larvae, which feed under the bark, that cause problems. They disrupt the flow of water and nutrients, which eventually girdles and kills the tree. The tree can die within two years of initial symptoms. White, green and black ash trees are equally tasty to EABs. Dieback usually starts in the top third of the canopy and works downward.

CONTROL — New treatment methods provide hope that this pest can be beaten. The new pesticide Tree-age^® did very well in 2007, its first year of use. It’s applied every other year by trunk injection and can only be purchased and applied by certified arborists or landscapers. In Canada, a similar treatment, TreeAzin^®, is working, too. Predator wasps native to China have been released in Indiana, where results are still pending.

You can help prevent movement of EAB by not transporting firewood or logs from quarantined states to others. For more information check out www.emeraldashborer.info. If you suspect your tree has an infestation, contact your local extension agency to report it.

Click on the photo to see the damage

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Three-lined potato beetle
Lema trilinea

IDENTIFICATION — True to their name, these beetles have yellow bodies with three black stripes running down their length. Their heads are red-orange with thick black antennae.

DAMAGE — Larvae and adults chew ragged holes in the leaves of datura, nicotiana, tomato, potato and some other vegetables in midspring to midsummer.

CONTROL — Handpick adults in early spring if you can see them. As soon as you see damage in spring, mix up and spray tops and bottoms of leaves with Bacillus thuringiensis (Bt), a beneficial bacteria you can buy in granular or liquid form. Repeat spraying every week or so until midsummer. Dust plants with Sevin^® in early spring to kill the beetles. To avoid scorching plant leaves, don’t apply Sevin in liquid form during the hottest part of the day or if temperatures are above 85 degrees.

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Tobacco budworm
Heliothis virescens

IDENTIFICATION — Tobacco budworm larvae are generally yellow to yellow-green with a brown head, but body color can sometimes be pink, red or maroon, as well.

DAMAGE — Most larvae appear in August or early September and attack petunia, geranium, nicotiana, ageratum, mum, snapdragon, strawflower, rose and other flowers. They tunnel into or eat entire flower buds and petals and sometimes leaf buds, too.

CONTROL — Handpick from plants around dusk when caterpillars are least active. Buy beneficial insects, such as stink bugs, green lacewing larvae and lady beetles from garden centers or mail-order sources, such as Gardens Alive. Release them on calm days in late spring, in early morning or early evening. Mix up pyrethroid insecticides and spray plants until leaves are dripping. These chemicals attack all stages of the insect, as well as the eggs, so you may only need to make a couple of applications.

asian lady beetles

Harmonia axyridis

Multicolored Asian lady beetles, or ladybugs, are beneficial, but you might not think so when they swarm your back porch or come indoors for a visit. Like the many other species of lady beetles, they feed on aphids and soft-bodied insect pests that attack flowers and vegetables. The best way to identify a multicolored Asian lady beetle from other species is by the distinctive “M” marking on the back just above the colorful wings. These lady beetles vary in color, from green to orange. And the number of spots on their backs varies.

Asian lady beetles don’t feed on wood, fabrics or human food. Nor do they sting, carry diseases or bite, although you may get a startling pinch from one. This pinch does not break the skin and is usually only a problem when your skin is moist on warm days. When you handle Asian lady beetles or step on them, they release a yellowish fluid that’s harmless but smells awful. And it can leave a stain. Always sweep up and dispose of dead beetles. Particles from the dried and crushed bodies can affect people with respiratory problems.

PHOTO: © Mary Jane Hayes

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Eastern tent caterpillar

IDENTIFICATION — There are several kinds of caterpillars that spin webs in trees, but you’ll see Eastern tent caterpillars and their webs in late spring or early summer. They’re black, with irregular blue and white markings and a solid white stripe down the back. Adult moths are about 1 in. long and red-brown with two white stripes on the front wings.

DAMAGE — Usually, the worst thing about these caterpillars is that their webs look messy, but the pests can defoliate and stress small trees. You’ll see webs in the forks of twigs or branches of trees east of the Rocky Mountains. Webs usually don’t enclose leaves, as the caterpillars leave the webs to feed. They generally feed in the morning or evening, when it’s cool, but may also feed during the day. If it’s raining or hot, they often retreat to the web.

CONTROL — You can pull down the webs, pests and all, and destroy them. Check the web first to be sure the caterpillars are “at home.” Wear gloves, because the hairs on the caterpillars can irritate some people’s skin. A strong jet of water can help knock down webs that are too high to reach.

Bt (Bacillus thuringiensis) is a common control, but it has to penetrate the webs to be effective. And you may need a professional to spray a large tree.

Click on the photo for a larger image

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Columbine sawfly
Pristophora aquiligae

IDENTIFICATION — These larvae of a non-stinging wasp have green heads and bodies without stripes or spots. You’ll often see them on the tops or undersides of columbine leaves in late spring.

DAMAGE — Larvae strip leaves by chewing along the edges toward the inner leaf, eating all but the midveins. Their green color blends in well with the leaves, so you may not notice them until they’ve done a lot of damage.

CONTROL — Many birds eat sawflies, so grow bird-attractors like berry and seedhead plants in your garden. Handpick, or spray insecticidal soap on the tops and bottoms of leaves every few days while you see the caterpillars. If most of the leaves are gone, cut the plant down to the ground and it’ll produce fresh foliage in a few weeks or come back the next year ready to bloom.

If you want, spray spinosad, an insecticide made from bacteria, on the leaves before or after you see the larvae (it works both when the caterpillars eat it or come in contact with it).

PHOTO: © Rick Wetherbee

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Slugs

IDENTIFICATION — These creatures can be ¼ to 7 in. long, and may be gray, orange, yellow, brown or black, with stripes or other markings. (The one in the photo at left is a banana slug.) Slugs are found almost everywhere, but prefer cool, moist areas like shade gardens or greenhouses.

DAMAGE — Slugs’ rasping mouthparts chew long, ragged holes in leaves. They can also damage or kill small seedlings and leave holes in fruits and vegetables.

CONTROL — Rake debris from beds in spring to remove slug eggs. Diatomaceous earth sprinkled on soil repels slugs because the sharp edges poke their soft bodies. Copper strips around plants repel them, too, as the strips generate tiny electrical charges that slugs don’t like. (You can buy both products at garden centers.)

For a bad infestation, you may need to use slug bait. Be careful to keep them away from children and pets.

PHOTO: © Neil Soderstrom

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Japanese beetle

IDENTIFICATION — If these pests weren’t so destructive, they’d be pretty. Shiny bronze-green adults are about 3/8 in. long. Larvae are 1-1/4-in.-long, C-shaped white grubs. These beetles are found in the eastern third of the United States and parts of Ontario and Quebec. They sometimes show up on nursery plants in the West, but they aren’t a common pest there yet.

DAMAGE — Adults feed on most plants, boring into flowers or fruit and skeletonizing leaves. Grubs eat grass roots, causing spongy, off-color patches in lawns.

CONTROL — If you see just a few, pick them from plants in early morning or late evening when they’re less active. A big infestation may need a general-purpose pesticide, but be sure it’s safe for the plant. Don’t use traps — they just attract more beetles. To control the grubs, try bacterial milky spore disease or parasitic nematodes (Heterorhabditis), which you can find at Gardens Alive! Both are watered into the lawn.

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Aphids

IDENTIFICATION — Orange, green, yellow, red, brown, black or covered with a waxy white or gray coating — there are all kinds of aphids out there. Most are 1/16 to 1/8 in. long, although some are bigger.

DAMAGE — Most aphid species are specific to one kind of plant, but they all pierce plant tissue, then suck out fluids. You’ll often find them in big clusters on new growth tips. A few aphids won’t hurt anything, but the population can grow rapidly. Large numbers of aphids cause curling, distorted leaves, yellowing foliage and stunted growth. They may also transmit diseases from plant to plant.

CONTROL — Keep an eye out for aphids. They reproduce so quickly that it takes no time at all before they’re all over your plants. Don’t overfertilize — high nitrogen causes lots of lush, tender new growth that attracts aphids. Prune out infested twigs and dispose of them, or hose aphids off plants with a strong jet of water.

Insecticidal soap controls aphids, but be sure to cover them completely with the spray. You can also use aphid predators, such as parasitic wasps and ladybugs, to feed on the pests. This control takes some time to work, so it isn’t the best way to get rid of aphids quickly.

Cut through the hype about organic methods for controlling pests in The Truth About Organic Gardening at right.

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Columbine leaf miner

IDENTIFICATION — If you have columbine, you’ll eventually have to deal with leaf miners.

DAMAGE — They don’t kill the plants but they can make the foliage look rough. Leaf miners, the larvae of a small brown fly, tunnel their way through the leaves like the one in the photo.

CONTROL — You can get rid of these tiny pests with a systemic pesticide, but simply removing the affected leaves and throwing them in the trash is easier and cheaper.

For a really bad case, cut the whole plant back after it flowers. The plant will send up new growth in a couple of weeks. By the time this new growth emerges, the leaf miners will be gone and you can enjoy the clean foliage the rest of the year. Come spring, your columbine will once again burst onto the scene with colorful abandon.

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Tobacco hornworm
Manduca sexta

IDENTIFICATION — These 3- to 5-in.-long giants of the caterpillar world have a large harmless spike, or horn, on their tails. Their green color blends into the foliage of tomato and tobacco plants, some of their favorite foods. They will also attack plants in the nightshade family, such as datura, petunia and nicotiana.

DAMAGE — In early to midsummer, caterpillars can quickly strip a plant of foliage and may sometimes even chew on green tomatoes.

CONTROL — If there are just a few caterpillars on your plants, handpick them. If numbers are larger, spray Bt on affected leaves only. Thuricide, which contains the kurstaki strain of Bacillus thuringiensis, works well on tobacco hornworm and is safe to spray right up to harvest, but be sure to wash fruit well before eating. Or grow alyssum, dill or Shasta daisy to attract braconid wasps, which lay dozens of eggs within each larva, parasitizing and killing it.

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Spider mites

IDENTIFICATION — You’ll probably notice the symptoms long before you see the actual pest. These little creatures are so tiny that they look like moving pencil dots. Two-spotted spider mites, the most common type, are found in most of the United States and into southern Canada. These equal opportunity pests feed on almost any plant and prefer hot, dry conditions, although some spider mite species prefer certain types of plants and like cool, damp weather.

DAMAGE — Spider mites feed on plants by piercing the leaves and sucking out fluids, eventually causing the entire plant to turn pale or bronze-colored. A bad infestation of spider mites can leave plants stressed and open to disease and other insects and may even kill young plants. You may notice webbing, usually on the undersides of the leaves. (Click on the photo to see webbing and individual mites between the lobes of the leaf.)

CONTROL — One easy way to get rid of spider mites is to knock them from the plants with a blast of water. Insecticidal soaps work well on these pests, too. Be sure to spray both the tops and bottoms of leaves until the plant drips.

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Whiteflies

IDENTIFICATION — If you brush the foliage of a plant and a white cloud floats up and quickly resettles, chances are your plant has whiteflies. Look on the undersides of the leaves and you’ll see the tiny white insects in the illustration.

DAMAGE — Larvae suck the sap from new leaves, which causes them to turn yellow and drop. Sometimes the young insects secrete sticky honeydew as they feed. The honeydew can harbor sooty mold, another symptom you may notice. It looks like black dust stuck to the leaf surface.

CONTROL — Whiteflies can’t survive cold winters, but overwinter on plants brought indoors and also on plants outside in southern zones with mild winters. Check everything you bring into your garden carefully. Also, check house plants before you bring them indoors in fall.

These tiny insects move through their life cycle so quickly that they can build up a devastating population in a matter of weeks. At each stage of life, they respond differently to controls. You can use yellow sticky traps to capture the adult whiteflies or knock the adults and larvae from the leaves with a strong stream of water. The larvae and eggs can also be rubbed from the leaves or use an insecticidal soap about once a week over several weeks to take care of them.

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Fungus gnat
Bradysia spp.

IDENTIFICATION — If you’ve noticed tiny flies that take flight from your house plants when you water, they may be fungus gnats. Fungus gnats are actually small dark gray flies about 1/8 in. long. They thrive with plenty of moisture and decaying plant matter. Most of their lives are spent as larvae feeding below the soil surface on organic debris and plant roots. After pupating, females can lay up to 300 eggs.

DAMAGE — Adult fungus gnats are generally considered a nuisance. But the larvae, in large enough numbers, can be a real problem. They feed on root hairs and small feeder roots, which causes stunted growth, off-color leaves or, in cases of severe infestation, leaf drop.

CONTROL — There are several simple ways to prevent fungus gnats from taking over. Avoid overwatering, use a sterile potting mix to keep from passing larvae along and remove plant debris from the soil surface.

If you do see these winged visitors hovering around your plants, cut a small cube of raw potato and push it into the soil of each plant to attract the larvae. Remove the potato piece after a few days and discard in the trash. Add another potato cube if you still see gnats around.

For severe infestations, try Gnatrol®. It’s a special strain of Bt bacteria (Bacillus thuringiensis), which is safe for home use. Ask for it at your local garden center.

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Boxelder bug

IDENTIFICATION — Chances are, you’ve noticed a swarm of these 1/2-in.-long, black-and-red insects loitering in sunny spots as the weather turns cool. And you’ve probably even hosted them in your home in fall and winter.

DAMAGE — Boxelder bugs don’t harm plants, people or property. They only swarm your home in the fall for warmth. You’ll probably notice the largest congregations on south-facing walls or pavement. But if their migration makes your skin crawl, you can help prevent them from using your home as a winter retreat.

CONTROL — These insects have long-distance stamina. They can fly up to two miles from their boxelder tree homes, so cutting down the boxelders in your yard isn’t the solution. Caulk all openings around windows and doors and in walls, siding and foundations to keep them out. The safest method of control is simply sucking them up in the vacuum cleaner. Because the insects do no real damage, insecticides may be a drastic measure. If you feel you have to, spray them with an insecticidal soap or insecticide that contains pyrethrins.

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Potato leafhopper
Empoasca fabae

IDENTIFICATION — You may never have seen a potato leafhopper up close before. They move quickly, scuttling sideways to hide under leaves, or simply flying to another plant. But if you can catch one, you’ll see that they’re pale green, 1/8-in. long and taper from the head in a wedge shape. There can be three or four life cycles in any location over a summer.

DAMAGE — Potatoes, eggplants, grapes, fruit trees and a range of shade trees — red maple, oak, redbud and hawthorn to name a few — are targets of these little pests. Leafhoppers feed by piercing leaves and sucking fluids out of the plant. Some plants show only a bit of spotting on the leves, but others may have leaves that turn brown at the edges and tips, and then die.

CONTROL — If you see symptoms or insects, spray the plants. Insecticidal soap works on leafhoppers, but it can be difficult to coat the entire insect because they move so quickly. Most systemic insecticides will take care of the problem (but don’t use these on edibles). Just read the label to be sure.