Good bug, bad bug: How can you tell the difference?
Contrary to common belief, most bugs are harmless. Here's how to tell the good guys from the bad guys and organic control solutions if you decide you have a problem.
Thu, Jun 28 2012 at 5:38 PM
If you’re the squeamish type, take a deep breath and think of the things that creep, crawl, slither, slide and flit among the plants in your garden as your friends.
“I have read that most insects are helpful or benign, as much as 90 percent of them,” Colleen Golden, senior horticulturist at the Atlanta Botanical Garden, said recently. “It may seem that many more than 10 percent of the insects out there are pests, but I think that is because we’re looking for them and also attracting them by growing plants they enjoy eating. Also, many of them are small and inconspicuous, so an untrained eye would have a hard time noticing them.”
As a result, she suspects that most people who see any bug in the garden automatically assume that it is “bad” or harming their plants.
To help you tell the difference between the good guys and bad guys, here’s a selection of six pairs of good bug-bad bug look-a-likes. We’ve included information about each, including how to identify them, reasons they are good for the garden or not and suggestions for ways to organically control the bad guys and keep them from bugging you, your plants or the vegetables you are planning to harvest.
Good bug-bad bug look-a-likes
Photos: Rove beetle (left) by John A. McLean, Jan Klimaszewski, Agnes Li, Karine Savard; Earwig by Mick E. Talbot
Good bug: Rove beetle (left)
Characteristics: Rove beetles are slender, less than an inch long. This is a large family of insects with many variations, but most rove beetles are gray or brown. The majority of their abdomen is visible because they have short wing covers. They scurry about, often flying or running. When they run, they often raise the tip of their abdomen in a way that resembles a scorpion, though rove beetles are harmless.
What attracts them to the garden: These insects look for moist environments such as decaying organic matter including leaf litter and fruits or vegetables that have fallen to the ground, compost piles, loose bark from fallen trees, dung and dead animals.
What makes them good: They feed on other insects, such as mites, flies, aphids, mosquitoes, fleas and fly maggots that infest carrion.
Controls: If you find these insects annoying, clean up the garden by removing decaying matter, and these beetles will disappear on their own.
Bad bug: Earwig
Characteristics: Earwigs are elongate, flattened insects less than an inch in length with colors ranging from light red-brown to black. A tell-tale difference between an earwig and a rove beetle is that earwigs have forcep-like pincers on the end of their abdomen. Immature earwigs resemble adults but do not have wings and are white to olive-green. They are nocturnal, feed on living or dead plant material and some insects and seek shelter during the day.
What attracts them to the garden: Like rove beetles, earwigs seek out moist, dark areas such as mulch, organic debris, cracks and crevices and spaces under flower pots.
What makes them bad: If they are in the garden in sufficient numbers, they can feed on and damage lettuce, strawberries, dahlias, marigolds, zinnias and roses. They also can become unwanted visitors to homes, often entering basements or crawl spaces through cracks and crevices and then making their way into living areas. They are not poisonous and, as a rule, don’t bite or sting humans. They can, though, pinch the skin with their forceps. If the mention of earwigs conjures up fables — that they enter the ears of sleeping people and eat their brains — or memories of "Star Trek II" — when Khan implants mind-controlling eels into the ears of two officers — rest assured, the fable is as fictious as the movie.
Controls: As with rove beetles, you can discourage earwigs from taking up residence in the garden by keeping the garden clean and free of hiding places such as leaf litter, stones and various debris. Keep them out of the house by moving mulches away from foundations, keeping shrubs trimmed, caulking and repairing cracks and crevices and making sure there is a tight fit around doors, windows and screens.
Good bug: Lady beetle (lady bird, lady bug)
Characteristics: Lady beetles, often called lady bugs, are not considered true bugs or insects. They include more than 5,000 species worldwide, with more than 450 native to North America. They are about a quarter of an inch long, are oval or dome-shaped and are usually yellow, orange, or scarlet with small black spots on their wing covers. Their legs, head and antennae are black. They are one of the most recognized “bugs” in the garden, perhaps because so many gardeners learned about them as children in the popular nursery rhyme, "Ladybird, Ladybird":
Ladybird, ladybird, fly away home
Your house is on fire and your children are gone
All except one, and that's Little Anne
For she has crept under the warming pan.
Your house is on fire and your children are gone
All except one, and that's Little Anne
For she has crept under the warming pan.
A myth about lady bugs is that the spots on their backs indicate their age. Actually, the size and shape of the spots indicate the species of the beetle.
What attracts them to the garden: They are drawn to home vegetable gardens in search of food, primarily soft-bodied insects such as aphids and scale, which find these voracious eaters anything but ladylike. Planting angelica or scented geraniums might also help attract them to your garden.
What makes them good: Aphids and scale are harmful to ornamental and vegetable crops, and lady bugs are a natural way of controlling these pests. In fact, the lady bug most frequently seen in American gardens is the multicolored Asian lady beetle, Harmonia axyridis, which was introduced by USDA Agricultural Research scientists in the late 1970s and early 1980s as a biological control agent for soft-bodied insects. Lady bugs are available for purchase for home garden use.
Controls: The only need to control lady bugs is when they enter your house, where the walls mimic the vertical cliffs where they overwinter in their home countries. The best way to keep them outdoors is to seal cracks and crevices and to make sure that doors, windows and screens have a tight seal.
Bad bug: Mexican bean beetle
Species, genus: Epilachna varivestis
Characteristics: The Mexican bean is regarded as a notorious garden pest and is one of the few harmful members of the lady beetle family. It is about a quarter of an inch long, copper in color and has eight black spots on each wing. Young bugs are yellow and covered with large spines. Adults lay yellow eggs in groups of 40-60 on the surface of lower leaves.
What attracts them to the garden: As their name suggests, these beetles are drawn to legume crops such as a variety of garden beans and cowpeas. Snap beans, especially wax beans, are a favorite host. Lima beans are also desirable targets. The Mexican bean beetle may overwinter in leaf litter that is not raked up in the fall.
What makes them bad: The adults and larvae feed on the undersides of leaves. A serious infestation can result in leaves that have a lace-like appearance. The beetles also feed on and destroy plant stems and pods. In sufficient numbers, the damage to the plants may so seriously affect the plant’s ability to make food through photosynthesis that the plants will weaken and die.
Controls: Selecting legume varieties that can be planted early and mature quickly will allow harvesting before the beetles have a chance to get established and do too much damage. Bush beans also seem to suffer less damage than pole beans. Turn crops under immediately after harvest to kill late-developing beetles and reduce the availability of sites where they can over winter.
Good bug: Spined soldier bugs
Species, genus: Podisus maculiventris
Characteristics: The spined soldier bug is the most common predatory stink bug in North America. Stink bugs have gotten this name because of the strong odor they emit when disturbed. Adults are about 1/2-inch long, shield shaped, vary in color from yellowish to pale brown, are covered with small black specks and have a conspicuous spine. They sometimes are confused with the common plant-feeding stink bug (Euchistus species). One way to tell the difference is the predatory spined soldier bug has more readily recognizable spines.
What attracts them to the garden: This is a generalist predator drawn to gardens by the availability of food sources, which are believed to include more than 100 insect species. Its favorite hunting grounds are on plants of potatoes, tomatoes, sweet corn, cole crops, beans, eggplant, asparagus, apples and onions. A perennial bed might also help attract them because it will provide shelter in all seasons.
What makes them good: These bugs prey on garden pests such as grubs, gypsy moth caterpillars, the larvae of beetles such as the Colorado potato beetle and the Mexican bean beetle, hornworms, imported cabbage looper, imported cabbage worm (also known as "broccoli worms"), webworms and armyworms. They kill their victims by harpooning them, injecting a paralyzing substance into them and sucking out bodily fluids through the harpoon.
Controls: None are necessary for this beneficial insect.
Bad bug: Squash bugs
Species, genus: Anasa tristis
Characteristics: Adult squash bugs are large insects, 5/8 inch long 1/3 inch wide. They are flattened, usually dark gray to brown in color and often have orangish and brown stripes. Eggs are yellowish to bronze and the nymphs go through five stages (called instars) on their way to becoming adults, going from light green to gray to brownish gray as they mature. Legs and antennae are black.
What attracts them to the garden: Squash bugs come to the garden to feed on squash pumpkins, melons, gourds and cucumbers.
What makes them bad: They pierce the leaves with their mouth parts and suck the sap out of the leaves. The feeding disrupts the plant’s ability to circulate water and nutrients. Excessive feeding can weaken a plant so severely that it dies.
Control: Young plants and those in flower are particularly susceptible to attack and gardeners should be vigilant for squash bug activity during these stages. The bugs are not harmful to humans and can be picked off the plants and squished between your fingers, those this may not be for the faint of heart! Other effective control methods are to knock them off the plant into a pail of soapy water where they will drown. You’ll have to be quick, as the bugs will scurry to hiding places if they can get away. Daron Joffe of Farmer D Organics in Atlanta likes to set a board or newspapers out in the garden because the bugs will congregate on these overnight. He catches them there huddled together early in the morning, and they can be quickly disposed of in soapy water. Eggs, which are usually laid in clusters of 20 between the veins on the undersides of leaves, should be crushed with the fingers or put in a sealed plastic bag and placed in the trash. Squash bugs can also be killed with organic sprays and soaps.
Good bug: Mealybug destroyer larvae
Genus, species: Cryptolaemus montrouzieri
Characteristics: The mealybug destroyer is a member of the lady bug beetle family and was imported to the United States from Australia in 1891 to control mealybug infestations in California citrus groves. They are effective predators in both their larval and adult stages. In its larval stage, the mealybug destroyer has a cigar-shaped body with wooly appendages and looks as if it has been rolled in flour. Adults are dark brown with a tan-to-orange head and posterior. Mealybug destroyer larvae look very much like the larval and adult stages of the citrus mealybug with one important difference: Mealybug destroyer larvae are at least twice as large as adult mealybugs. As an adult, an mealybug destroyer measures less than 1/8 inch long.
What attracts them to the garden: Food sources, primarily mealy bugs, aphids and soft scale.
What makes them good: Mealybug destroyers attack their prey at different stages of development, devouring mealybug eggs as soon as they hatch. The eggs are the favorite food of young mealybug destroyer larvae and the adult mealybug destroyer. Older larvae will consume mealybugs at all stages. They will also eat scale at some stages and aphids.
Control: There is no need to control this beneficial pest. If anything, gardeners should be acutely aware of the difference between mealybug destroyers and mealybugs so they don’t kill this helpful insect.
Bad bug: Mealybugs
Species, genus: Primarily Pseudococcus longispinus; also, citrus mealy bugs, Planococcus citri
Characteristics: Mealybugs are a common pest whose infestations can be identified by a characteristic fuzzy, white mess they secrete onto the stems and leaf nodes of plants. The individual bugs are tiny (about a tenth of an inch long), white, soft-bodied insects with fringes around their bodies and, depending on the species, twin tails. When they move about on the plant, they resemble a tiny white cottonball scurrying along. The bugs seen on plants are the females. Males are about the size of gnats, have wings and are rarely visible. Mealybugs can invade both inside and outside plants. Signs of mealy bug damage include anemic-looking plants with unhealthy foliage and ants, which are attracted to the honey dew.
What attracts them to the garden: Over watering and over fertilizing.
What makes them bad: Mealy bugs damage plants, including houseplants, by sucking liquids out of them. They particularly like to attack tender new growth. Their damage causes leaves to turn yellow fall off. They can also attack fruits, vegetables and flower buds, causing them to prematurely drop off. While eating, mealy bugs excrete a sticky wax substance (called “honeydew”). A sooty mold fungus can develop from their excretions, colonize and spread. The mold keeps parts of the plant from photosynthesizing and results in aesthetic damage.
Control: If you just see a few mealybugs, they can be killed by dipping a cotton tip in isopropyl alcohol and daubing the insect with it. Commercially available insecticidal soaps and horticultural oils are usually effective in controlling mealybugs. If the mealybugs keep coming back, it’s a good idea to quarantine the plant as you continue to treat it. If they continue coming back in quarantine, you may have to destroy the plant to keep the infestation from spreading. Mealybugs cam live in the soil on the roots, so treatment should include soil drenchs as well as foliar sprays. When bringing houseplants that have been spent the summer outdoors inside for the winter, check them carefully for hitchhiking mealybugs.
Good bug: Bigeyed bug (left)
Characteristics: Insects in the genus Geocoris are beneficial predators in both their nymph and adult stages. Adults are often confused with the true chinch bug, which is a true pest. Adult big-eyed bugs are small (1/8 to 1/4 inch long) black, gray, or tan and and have broad heads with large, curbed, backward-projecting eyes, from which they get their name. Females deposit eggs singly or in clusters on leaves near potential prey.
What attracts them to the garden: These are very common insects found all across the United States in many different types of turf and gardens.
What makes them good: They feed on mites, insect eggs and whiteflies. Nymphs and adults are general predators and feed on small caterpillars and caterpillar eggs, small insects such as pink bollworm and cabbage loopers, fleahoppers, Photo: Hover fly (left) by Christine Majul, Yellow jacket by Audreyjm529
Good bug: Hover flies
Family: Numerous species in the Syrphidae
Characteristics: Many hoverflies mimic various bees and wasps with color patterns that are often black and yellow color and in the way that they will push the tip of their abdomen into your fingers or hand if they are caught and held. Hoverflies, however, are harmless and do not have the ability to sting as a yellow jacket would. They are speedy fliers and get their name from their ability to hover over flowers while nectaring. They are sometimes called flower flies.
What attracts them to the garden: The nectar and pollen of flowers and honeydew produced by aphids. Feverfew, coreopsis and Italian parsley that is allowed to flower are just a few of the plants that will attract hover flies.
What makes them good: Adult hoverflies feed on honeydew produced by aphids. The slug-like larvae of hover flies are often found among aphids, a favorite food of the larvae. Research is continuing, but it is believed that hover flies contribute to pollination of some vegetables and various fruit trees.
Control: None is necessary for these beneficial insects.
Bad bug: Yellow jackets
Characteristics: Many people think of yellow jackets as a bee, but they actually belong to the wasp family. They are among the most recognized visitors to the garden and, possibly, the least liked. That’s because yellow jackets are aggressive, especially if their nest is disturbed, and their stings are painful and lingering. For those who are allergic to their venom, the stings can be fatal. Most yellow jackets are black and yellow, are about the size of a honey bee, nest in colonies and fly in a rapid, side-to-side motion before landing. They often build their nests underground in places such as an old rodent burrow, beneath landscape timbers, in rock walls or the walls of a building.
What attracts them to the garden: They are drawn to the garden by flowers rich in sugars and carbohydrates, such as fruits, flower nectar and tree sap. The larvae feed on proteins, such as insects, meats, and fish. Open sugary drinks and food brought outside will also attract them, as will potential nesting sites.
What makes them bad: Painful stings make this bug the poster child bad boy of the insect world.
Control: Killing the nest is the best way to eliminate yellow jackets. This should be handled with great care and may best be left to professionals.
Golden, the Atlanta Botanical Garden senior horticulturist, says there are other beneficial insects that gardeners should be aware of including lacewings, assassin bugs, praying mantids and minute pirate bugs. An important thing to know about all of these insects is that they go through different life stages in which they can look completely different than in the adult stage, she says. Some of the insects go through the egg, larva, pupa, adult life cycle, and others go through an egg, nymph, adult life cycle. Regardless of which life cycle an insect has, it can still look markedly different from one stage to the next. This is important, Golden says, because being able to recognize these different stages and allowing the good guys to stay in your garden can help you beat a pest problem.
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