Florence Grovida Gardening

Identifying beneficial insects

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Insects that prey on or parasitize insect pests are called beneficial insects. Whether you know it or not, you rely on these allies to help keep the insect balance from tipping too far in the destructive direction. If you familiarize yourself with these good guys, you can encourage their presence in the garden and avoid killing these innocent bystanders just because they happen to be the insects you spy on your favorite dahlias.

You can buy many of these beneficial insects from mail-order catalogs to increase your local populations. See the "Sources of beneficial insects" sidebar, later in this chapter.

The following beneficial insects are worth befriending:

• Big-eyed bug: These fast-moving, to /4-inch bugs have tiny black spots on their heads and the middle part of their bodies, as shown in Figure 7-1. They dine on aphids, leafhoppers, spider mites, and some small caterpillars. Because these bugs aren't commercially available, look for them on nearby weeds, such as goldenrod or pigweed, and relocate them to your garden.
• Braconid wasps: Several species of braconid wasps, shown in Figure 7-2, parasitize pest insects. Both the slender adults and tiny, cream-colored grubs feed on a range of pests, including aphids, cabbageworms, codling moths, and corn borers. Purchase these Xo- to /2-inch wasps from suppliers and plant some dill, fennel, and other parsley-family flowers to help keep them around. Adults require carbohydrate food, such as the honeydew secreted by aphids, tree sap ooze, or flower nectar.
• Centipedes: Indoors and out, multilegged centipedes feed on many insect pests. Most species don't bother humans (unless you count the screech with which they are frequently greeted), and while some southwestern species do inflict a temporarily painful bite, none are dangerous. You can't do much to encourage their presence, but if you can leave them alone to do their job, you'll have fewer insects around.
• Damsel bugs: These slender, %- to X-inch bugs have strong-looking front legs. They prey on aphids, caterpillars, leafhoppers, and thrips. Damsel bugs are common in unsprayed alfalfa fields, where you can collect them in a net for relocation to your yard.
• Ground beetles: Many beetle species live in or on the soil, where both their larval and adult stages capture and eat harmful insects. They vary in color (black, green, bronze) and in size. Although most live close to the ground, feeding on aphids, caterpillars, fruit flies, mites, and slugs, the 1-inch-long caterpillar hunter beetle climbs trees to feed on gypsy moths and other tree-dwelling caterpillars.

Because these beetles aren't available commercially, the best thing you can do to encourage their presence is to avoid using herbicides and insecticides. Also, learn to distinguish them from unwanted insects. Most of the helpful ground beetles are large, dark, and fast moving. They often have nasty-looking mandibles and eyes on or near the fronts of their heads.

• Hover flies: These insects get their name from the adults' habit of hovering around flowers. The adults, resembling yellow jackets, are important pollinators; the brownish or greenish caterpillar-like larvae have an appetite for aphids, beetles, caterpillars, sawflies, and thrips. If you grow an abundance of flowers, you're likely to see hover flies.
• Ichneumonid wasps: Ichneumonid wasps are valuable allies in controlling many caterpillars and other destructive larvae. The dark-colored adult wasps (see Figure 7-3) vary in size from less than 1 inch to 1/2 inches, and they have long antennae and long egg-laying appendages — called ovipositors — that are easily mistaken for stingers. The adults need a steady source of nectar-bearing flowers to survive.
• Lacewings: The delicate green or brown bodies and transparent wings of these /*■ to /4-inch insects, shown in Figure 7-4, are easy to recognize in the garden. Adults live on nectar. The spindle-shaped, alligator-like, yellowish or brownish larvae feed on a wide variety of soft-bodied pests, such as aphids, scale, thrips, caterpillars, and spider mites. Each of the distinctive, pale green, oval eggs sits at the end of its own long, thin stalk on the underside of a leaf. You can purchase lacewings as eggs, larvae, and adults. To keep the welcome mat out for the adults, allow some weeds to flower nearby.

✓ Lady beetles: The convergent lady beetle, also called a lady bug, is what most people think of when they praise lady beetles' appetite for aphids. Both adults and larvae prey on soft-bodied pests, including mealybugs and spider mites. The convergent lady beetle larvae look like small, black, segmented pillbugs with rows of knobby or hairy projections and four orange spots on their backs. (This species is distinguished from her damaging pest cousin, the Mexican bean beetle, by two converging white lines on the thorax — the segment between the head and the abdomen. The number of spots varies widely.)

If you plan to purchase and release lady beetles, prevent them from flying away by setting out another food source, such as an artificial yeast/sugar or honeydew mixture, which is available from commercial lady beetle suppliers. See the "Sources of beneficial insects" sidebar, later in this chapter.

• Minute pirate bugs: These bugs have an appetite for soft-bodied insects, such as thrips, corn earworms, aphids, and spider mites. A single bug can consume 30 or more spider mites a day! The adults are M inch long, somewhat oval-shaped, and black with white wing patches. The fast-moving, immature nymphs are yellow-orange to brown and teardrop-shaped. You can purchase them for release in your yard.
• Predatory mites: Similar in appearance to pest mites, predatory mites are tiny (smaller than /2s inch) and quick. They feed primarily on thrips and pest mites, and are widely used to control these insects in commercial orchards and vineyards. They are available to home gardeners as well, from the places listed in the "Sources of beneficial insects" sidebar, later in this chapter.
• Praying mantises: Because these curious-looking insects eat as many beneficial insects as pest insects, they're not among the most useful of the beneficial insects. Other beneficials that target specific pests usually are more effective.
• Rove beetles: These beetles have the distinctive habit of pointing their abdomens upward as they walk. Decaying organic matter is their home, where they feed on soil-dwelling insects, such as root maggot eggs, larvae, and pupae (especially those of cabbage and onion maggots). In mild, wet climates, they also eat slug and snail eggs.
• Soldier beetles: The favorite diet of both the adults and larvae of these common beetles consists of aphids, caterpillars, corn rootworms, cucumber beetles, and grasshopper eggs. The adults, shown in Figure 7-5, are slender, flattened, and /3 to /2 inch long. The larvae are the same shape and covered with hairs. They spend much of their life cycle in the soil, so they will be more prevalent in areas where the soil is undisturbed.
• Spiders: All spiders are predators, ridding the garden of many common pests. You can provide good habitat for spiders by mulching with hay and straw, which has been found to reduce insect damage by 70 percent due solely to the numbers of resident spiders.
• Spined soldier bugs: Adult spined soldier bugs dine on the larvae of Colorado potato beetles, Mexican bean beetles, and sawflies, as well as European corn borers, cabbage loopers, and tent caterpillars. The adults, shown in Figure 7-6, resemble tan, shield-shaped stinkbugs with prominent spurs on their shoulders immediately behind the head. They pierce their victims with a harpoon-like mouth. You can purchase them for release in your garden.

Figure 7-5:

Soldier beetle.

Figure 7-5:

Soldier beetle.

Figure 7-6:

Spined soldier bug.

Figure 7-6:

Spined soldier bug.

• Tachinid flies: These large flies feed on tent caterpillars, armyworms, corn borers, cutworms, stinkbugs, and other pests. The adult fly is about the size of a housefly and may hover above squash plants in search of prey. It has a bright orange abdomen, black head and thorax, and a fringe of short black hairs on the hind legs. Coriander, coyote brush, evergreen euonymus, fennel, goldenrod, and white sweet clover attract these flies to your yard.
• Tiger beetles: A variety of brightly colored and patterned, /2- to /4-inch beetles fall into this group, and they all have distinctively long legs. They feed on a wide range of soil-dwelling larvae. If you use an electric bug-zapper light, you're inadvertently killing these garden allies.
• Trichogramma wasps: Tiny as pencil points, these parasitic wasps inject their eggs inside the eggs of more than 200 species of moths, and the developing larvae consume the host. Buy these wasps commercially, and release them during their hosts' peak egg-laying times. Suppliers can give you more specific directions on release times.
• Yellow jackets: I know it's hard to think of these annoying insects as beneficial, but they do help rid your garden of flies, caterpillars, grasshoppers, and many larvae by taking them home to their young. Yellow jackets are fond of white sweet clover and ivy, so expect to see them near your house if you have either type of plant nearby.

You can take important steps to welcome beneficial insects to your yard and encourage those you purchase to stick around:

✓ Wait to release beneficials until you've seen their favorite prey in the garden. If beneficials don't find any food in your garden, they move elsewhere. You can purchase food for lady beetles (from the companies that sell the beetles) to encourage them to stay even after aphid populations decline, for example.

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