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"Good Bug" Guide
Think before you spray a pesticide
You may kill the insects that are helping you keep pests in check. This means you will have to spray more in the future. Also, insects benefit your garden by pollinating your plants, helping them grow and propagate.
How to make your good bugs feel welcome
Beneficial insects are more likely to remain in your garden if there is a ready food supply. While you can buy many of these predators, it's probably cheaper and more effective to encourage the ones already in your garden. Many beneficial insects need to sip flower nectar to survive. Plan your garden to feed beneficial insects by choosing a variety of plants that will bloom as many months of the year as possible. Here are some things you can do to support your beneficial insect population:
- Plant nectar-producing flowers to further increase the food supply. Plants in the cabbage, carrot and sunflower family are especially attractive to beneficial insects.
- Control ants, which may prevent predators from controlling aphids.
- Don't use persistent, broad-spectrum, contact insecticides. These provide only temporary pest control and are likely to kill more of the natural enemies than the pests. When their enemies are gone, pest populations may soar and become more of a problem than before they were sprayed.
- Cover bare dirt in your garden with mulch of dead leaves or grass clippings, thick enough to shade the soil surface. This provides shelter for spiders, which are the number one predator on insects. (Most of these spiders are tiny.)
Don't forget the birds
Birds can also be very helpful with controlling pests in your garden. Trees, shrubs with berries, birdhouses and water features all encourage birds to visit your yard.
How to recognize
This aptly-named, vicious-looking bug is about 1/4 to one inch long, with a cone-shaped head and wide curving beak. They may cause a painful bite to a human if captured. Some species squeak if caught. Females lay single eggs in cracks, under rocks or in other sheltered spots in summer, and new adults emerge around the following June. There is only one generation per year.
Benefits
Assassin bugs are voracious predators of many garden pests including flies, mosquitoes, beetles and large caterpillars.
Fun fact
Adult and nymph assassin bugs stab their prey with long, pointed "beaks" that are held folded under their bodies while not feeding.
Other notes
A related family of smaller predatory insects that wait for their prey on flowers are called ambush bugs.
Examples
Dipel, Thuricide, Safer Caterpillar Killer
Effective Against
Tent caterpillars, gypsy moths, cabbage loopers, and other leaf-eating caterpillars.
When To Use
Use B.t. only if pests cannot be removed by physical means such as pruning or hand removal. It is essential to treat when larvae are young and feeding, but before too much damage has occurred. At this stage, some larvae will be seen outside the tent. (once caterpillars begin to pupate, it is too late to spray.) Applications may be repeated at 3 to 14 day-intervals as needed.
How To Use
Read the label before using and take all specified precautions when applying. Check to see that this material is registered for your crop or plant. B.t. is a stomach poison, not a contact poison, so the caterpillars must eat it. Spray infested plants to provide a thorough coverage of foliage. it may take several days for the caterpillars to die. Be sure that the product is fresh when purchased, the bacteria become inactive as the product ages or if exposed to extreme temperatures.
Benefits
Selective to caterpillars. Relatively non-toxic to humans, pets, birds, and beneficial insects (except caterpillars).
Concerns
Toxic to caterpillars that become beautiful butterflies. Timing of spray is critical (see above). Some species may develop resistance if overused. Some people may experience allergic reaction or skin irritation from contact with the material.
How to recognize
These insects resemble a yellow jacket but are larger, up to 3/4 inch in length. They are mostly black, with a white face and white markings on the tip of the abdomen. They build large paper nests that can measure up to 14 inches in diameter and 24 inches long!
Benefits
They eat many pests including crane flies and other flies. They also eat yellow jackets. They may also act as pollinators of some plants.
Concerns
If the nest is disturbed, these hornets will sting humans.
Fun fact
Often called "insect hawks" because they pounce upon pests.
Examples
BioSafe, Scanmask, Biovector, Nemesis.
Effective Against
Cranefly larvae (leatherjackets), flea larvae, root weevils.
When To Use
Nematodes should be applied during the late spring to to fall months when larval pests are present and soil temperatures are warm enough. BioSafe requires at least 55 degrees F. For craneflies, monitor first in early April by removing several one foot square areas of sod, tearing them apart, and counting the number of grubs. If more than 25 grubs per square foot are found, you, can use nematodes if soil temperature is high enough. For flea larvae, apply to lawn areas in summer if flea populations require it and indoor flea controls are not sufficient. A second application may be needed after 6 weeks to 2 months. For root weevils, apply in spring after soil temperatures warm. A second application is suggested in late summer or fall.
How To Use
Product must be purchased new each year and used by the date on the container. Dry formulations must be mixed with water as directed and applied with a sprayer or a watering can as indicated on label. Sprayers work best for lawn applications, watering cans are fine for smaller applications. Do not apply until soil temperatures reach required temperatures. Do not apply in direct sunlight. Store product as directed, avoiding temperature extremes. Water the soil thoroughly before applying, and keep moist throughout the six weeks nematodes are active in the soil. Nematodes will die if there is either too much or too little water.
Benefits
Non-chemical control is not toxic to humans, pets, or beneficial insects. Effective against a number of serious pests that live in the soil.
Concerns
Cool soil temperatures prevent early application in spring for Cranefly. For summer flea control, lawn must be kept watered, and fleas must also be controlled on pets and in indoor areas with other methods. Product is fairly expensive. Effectiveness not as high as chemical controls but is adequate to reduce damage below levels that threaten plants.
Provides these benefit(s):
Pollination
How to recognize
Large and lumbering, black and yellow bumble bees measure up to one inch in length. These fuzzy insects make a loud droning buzz as they fly somewhat awkwardly from flower to flower. Bumble bees nest in soil or leaf litter where a single queen lays 8 to 12 eggs in spring and continues to lay eggs through the summer.
Benefits
Emerging workers are able to fly in very cool weather, making them a very valuable pollinator of a variety of plants.
How to attract
As these bees nest in soil and leaf litter, try to leave a section of your yard undisturbed. A little "wild" place in your yard can offer a haven for many other beneficial insects that would otherwise be killed by tilling and mowing. Provide native flowers, as they are a primary food source.
Fun fact
There may be as many as 40 species of bumble bee in the Western U.S.
How to recognize
This long (1/2 to three inches) many-legged creature is light brown to black in color and moves quickly. Centipedes have only one pair of legs per segment. Millipedes, which are important in compost decay, have two pairs per segment. Both prefer moist areas in the garden and compost piles.
Benefits
Centipedes prey on pests and insects in the soil including slugs, worms and fly pupae. Centipedes kill their prey with venom, and their bite is moderately painful (although not dangerous) to humans.
How to attract
As with ground beetles, low-till gardening can maintain the populations of centipedes.
How to recognize
There are more than 80 species in Washington. They can be identified by their long narrow body, their large compound eyes and the four transparent wings. There is variation in color. Sizes range from one to two inches. The larvae are found in water.
Benefits
They eat mosquitoes, aphids and other pest bugs.
How to attract
Dragonflies and damselflies have decreased considerably in abundance as the wetland areas where they live have dramatically decreased. Want dragonflies? Don't fill in that marshy area. Better yet, enlarge it, or dig your own pond.
How to recognize
Adult green lacewings have delicate, light green bodies; large clear wings; and bright golden or copper colored eyes. They are 1/2 to 3/4 inch long. The larvae are small, grayish brown, and narrow and they have pincerlike mandibles. Eggs are found on plant stems and foliage; they are laid singly or in small groups on top of fine, silken stalks.
Benefits
Lacewing larvae and adults feed voraciously upon aphids and other small insects, insect eggs, and spider mites. They also eat leafhopper nymphs, whiteflies and small caterpillars.
How to attract
Plant flowers that produce pollen and nectar. Adults are mobile, but lay eggs where they stop to eat.
If you buy
Success with lacewing eggs or larvae may require practice. Hold eggs at room temperature until the larvae begin hatching, then sprinkle them on plants (about one to five per square foot of garden space).
How to recognize
While shapes and colors may vary widely, they are usually shiny. Some are very ferocious-looking, but they are not known to bite people. Black is a common color, sometimes with a metallic sheen of another color on their wing covers. Most ground beetles feed at night and hide in the soil or under debris during the day. Adult beetles range from 1/8 to one inch long.
Benefits
These very common garden insects feed on many soil-inhabiting pests such as cutworms and root maggots. Some types eat slugs and snails.
How to attract
You probably don't need to attract these common beetles. Unless it's discouraged with pesticides, the species that is right for your garden will find you. Low-till gardening techniques can save the lives of many soil-dwelling ground beetles. Objects to hide under, such as logs, boards or flat stones, will help keep ground beetles in your garden.
Provides these benefit(s):
Pollination
How to recognize
Adults measure 2/3 inch long and are fuzzy, with gold-and-black striped bodies and transparent wings. Honey bees can often be identified by the balls of yellow pollen they carry on the backs of their legs.
Benefits
Honeybees are important pollinators of many plants.
How to attract
Grow flowering plants. Encourage wild honey bees. Because the spread of mites has seriously reduced honey bee populations, the wild honey bees that are left are even more important.
Fun fact
Pollinators are estimated to be worth $8 billion to our economy! Many other insects are pollinators as well.
How to recognize
The adults have bodies with black and yellow stripes. While they look like bees or wasps, they don't sting. They range in size from less than ¼ inch to ½ inch.
Benefits
Although not all are directly beneficial, many hover fly larvae prey on aphids, mealybugs and other small insects. Adults must feed on nectar before they reproduce, so are good pollinators.
Fun fact
These flies are called "hover flies" because they hang in one spot like a helicopter when they fly.
How to recognize
Most people know an adult lady beetle (lady bug), but the larvae are most valuable. The larva is soft-bodied and alligator-shaped with black and orange markings. Each species has a distinct pattern.
Benefits
Both larvae and adults feed on soft-bodied insects such as aphids, mealybugs, scale insects and spider mites as well as insect eggs.
How to attract
Plant flowers that produce pollen and nectar (dill, angelica). Allowing weeds (dandelion, wild carrot, yarrow) can help too. You could also spray a combination of whey and yeast on plants as a food source.
If you buy
We don't recommend buying lady beetles for pest control: most often they won't stay in your garden when released. The best thing is to attract lady beetles, or other insect predators, to your yard.
Provides these benefit(s):
Pollination
How to recognize
Slightly smaller than a honeybee, these gentle, non-aggressive insects resemble house flies more than honey bees. They are deep blue-black in color and have no stripes.
Benefits
Mason bees pollinate apples, cherries and other tree fruit. They are active between apple blossom and cherry blossom season, then die out by summer.
How to attract
Provide them a home. Drill holes 1/4 to 3/8 inch in diameter and 3 to 6 inches deep into wooden boards or blocks. Attach boards to a house or post near where you have seen the bees. Some protection from rain is a good idea. Position boards facing morning sun. Place homes by early spring, preferably by April 1.
How to recognize
Too small to be noticeable, these miniwasps don't sting people or pets. They range in size from the smallest insect known (about 1/50 inch) to about one inch, although most are on the small side. These parasites reproduce by laying their eggs in a pest host (adult or egg). The immature wasp feeds inside and kills its host. A round hole can be often seen where the adult parasite has chewed its way out.
Benefits
Different species may attack aphids, whiteflies, and butterflies or moths, such as cabbage loopers and hornworms.
How to attract
You need to have some of the prey around to be able to sustain populations of the parasite.
If you buy
Many are available for sale to home gardeners. Examples are Encarsia formosa, which attacks greenhouse white flies, and Trichogramma species, which attack many caterpillar pests.
How to recognize
Adult mites are tiny, about half a millimeter in length, and are beige to reddish tan. They resemble pest mites but are faster moving and have fewer hairs.
Benefits
Predatory mites are valuable predators of pest mites such as spider mites.
How to attract
There is no great way to attract mites. Since you probably already have some, don't discourage them with pesticides.
If you buy
Predatory mites naturally occur in large numbers in the Northwest. Since you probably already have mites in your garden, it may not make sense to buy new ones for outdoor use. However, they may be useful for greenhouses and indoor plants. They are especially effective against spider mites. You can purchase predatory mites at many garden stores.
How to recognize
These fascinating insects may resemble a tiny scorpion when they hold the tip of their abdomen up in the air. They are fast moving and measure 1/10 to one inch long.
Benefits
Depending upon species, rove beetles prey upon aphids, springtails, mites, nematodes, slugs, snails, fly eggs and maggots. They also eat and help break down decaying organic material.
How to attract
Create a "wild" area of your yard where leaves are allowed to pile up,the grass isn't mowed, and the soil isn't tilled. This can give these and many other insects a haven.
Fun fact
Rove beetles are often seen hanging around dead animals but they're not scavengers. They're actually waiting for their prey, such as flies and maggots.
How to recognize
Approximately 1/2 inch in length, the adult soldier beetle has a narrow, black abdomen and bright red head or thorax. The soldier beetle larva is various shades of orange with black markings.
Benefits
Soldier beetles prey upon aphids, caterpillars, grasshopper eggs and beetle larvae, among other insects around the garden.
How to attract
Since some soldier beetles feed on nectar, you may be able to attract them with flowering plants.
Fun fact
Soldier beetles are nicknamed leatherwings because of their soft, clothlike wing covers.
How to recognize
Spiders aren't insects at all. They can be identified by their eight legs and two-part body. Although there are hundreds of species of spider in Washington, they all share this trait. Spiders are far more beneficial than they are dangerous. Most spiders are shy and harmless to humans.
Benefits
Spiders are the most important predators on insects, killing more than all other predators combined. They feed on a broad variety of pest insects year-round.
How to attract
You probably already have an abundance of spiders. You can provide spider habitat by covering bare dirt with mulch, creating a "wild" area in your yard, planting dense shrubs and coniferous trees, and providing a water source such as a pond.
If you are concerned about spiders in your home, sealing off your living space from the crawlspace, garage, floor voids and unfrequented storage space will help. House spiders and outdoor spiders are not the same species.
How to recognize
Resembling house flies, tachinid flies are 1/3 to 1/2 inch in length and may be brown, gray or black in color. Some species are very hairy.
Benefits
There are many species of tachinid flies; many are parasites of pest caterpillars including cutworms, codling moths, tent caterpillars, cabbage loopers and gypsy moth larvae.
How to attract
Adults feed on nectar, so plant flowers as well as herbs in the Umbelliferae family such as dill, parsley and Queen Anne's Lace.
How to recognize
Adult wasps are 1/2 to 3/4 inch long, with characteristic yellow and black stripes and transparent wings.
Benefits
Yellow jackets and other wasps are predators of caterpillars, flies and beetle grubs.
Concerns
Yellow jackets are often feared for their sting, which is a hazard to people who are allergic. Some yellow jacket species are more likely to sting and scavenge at picnics than others. The scent of pears is a sting signal for yellow jackets.
How to attract
Think about that nest in your yard: Does it really have to go? If the yellow jackets are not interfering with the lives of people in the area, leave the nest alone and get great pest-control and pollination benefits.
Other notes
To occupy yellow jackets during a picnic, place raw meat or a fish head away from the picnic (over a bucket of soapy water).
