Predator And Parasitic Insects

Many gardeners assume that every bug they see is destructive. The truth is that of the approximately 80,000 species of insects in North America, over half are beneficial. Most of these insects work in two ways to help keep the destructive insects in your garden under control.

First, predator insects, mites and molluscs destroy garden pests. Some of these insects have large mouthparts that allow them to tear up and devour their prey. Others have piercing mouthparts with which to suck the body fluids from other insects. Predators include antlions, dragonflies, a few true bugs and a number of beetles: blister beetles, carrion beetles, ladybugs, net-winged beetles, soldier beetles, soft winged beetles and tiger beetles.

You can often identify predacious beetles by sight. If a beetle's jaws are short and chunky, it is a plant eater. If the jaws are long and pointed with sharp cutting edges, it destroys other insects. Although most true bugs are destructive, a few are extremely helpful. Pirate bugs feed on small insects and mites. Some stink bugs are predacious on the Colorado potato beetle. And assassin bugs attack Japanese beetles and other harmful insects.

Parasitic insects deposit their eggs on or in other insects. Many have an egglaying device called an ovipositor that allows them to pierce the bodies of other insects to lay eggs. When the eggs hatch, the larvae feed inside the victim's body. Some of these parasitic insects lay their eggs in a number of host species, but others attack only one.

Probably the most popular commercially available parasite is the trichogramma wasp. It lays eggs in more than two hundred harmful species. Thousands of other wasps (some are called flies) are useful in controlling garden pests—ichneumon flies, braconid wasps, aphid wasps and pelecinid wasps to name a few. Although almost everyone considers flies obnoxious household



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Here are the most important beneficial insects you can obtain commercially:-

The larvae of the green lacewing are active against mealybugs, scale and aphids. Once introduced into the garden as eggs, they hatch in a few days and feed for about three weeks, pupate and emerge as adults. Adults feed on the so-called honeydew that aphids excrete. Lacewings are shipped from the insectory as eggs in rice hulls.

Ladybugs eat two and a half times their weight each day in aphids, mealybugs, moth eggs and spider mites. The larvae also consume a number of insects. Ladybugs are probably most popular of all beneficial insects. Unfortunately, most will leave your garden within a few days of being released.

The mealybug destroyer is a member of the ladybug family that prefers mealybugs. The larvae consume aphids as well.

Parasitic nematodes attack borers and soil-borne grubs. A few firms offer them for sale.

Of the parasitic wasps, Encarsia formosa attacks the common whitefly larvae, Aphytis melinus attacks red scale and Trichogramma parasites the eggs of corn earworm, cabbage worms and other larval pests.

The praying mantis, a large, dramatic-looking insect, consumes huge quantities of beetles, caterpillars, and grasshoppers. The young eat aphids, flies and other small insects.

Predatory mites feed on plant-damaging spider mites. They are most effective when a mixture of species is released. To encourage beneficial insects to prey and parasitize in your yard, grow pollen-rich flowers around the garden. Strawflowers attract ladybugs. Qoldenrod hosts over 75 beneficial species. Dandelion, wild carrot, lamb's quarters and evening primrose are also useful.

You can buy a yeast-sugar insect food sold as artificial nector. Spray it across the garden and yard. Beneficial insects such as ladybugs and adult lacewings will feed on it just as they do on honeydew secreted by pests or flower nectar. You can make your own solution by combining equal parts of brewer's yeast and sugar with enough water to dissolve them completely. Apply either solution with a hand-pump sprayer.


Some bacterial agents are extremely effective against garden insect pests. Bacillus thuringiensis, sold under the names Thuricide, Biotrol, Agritrol and Dipel, produces a toxin that paralyzes the digestive system of caterpillars including cabbage loopers and tomato hornworms. It does not harm birds, bees, pets or humans.

Bacillus popilliae (sold under the names Doom and Milky Spore Disease) helps control the beetle grub.

Grasshopper Spore contains a natural parasite that attacks grasshoppers. The effect of this parasite is slower to show results, but can be effective if used over several seasons.


Plants themselves are the source of some of the strongest insecticides around.

Pyrethrum is made from the dried and powdered flowers of Chrysanthemum cineraefolium, a close relative of the garden chrysanthemum. Pyrethrum is extremely effective against aphids, leafhoppers, thrips and leaf miners.

Rotenone is an insecticide derived from the roots and stems of tropical shrubs and vines in the genera Derris and Lonchocarpus. Rotenone acts on contact and is also a stomach poison. It controls many sucking and chewing insects including beetles, caterpillars, leaf hoppers, thrips and aphids.

Ryania is derived from the ground stems of Ryania speciosa, a tropical South American shrub. It is especially effective against the European corn borer as well as a variety of other insects.

Sabadilla, made from the seeds of a lilylike Mexican plant (Schoenocaulon officinale) is sold as wettable powder. It works as both a contact and a stomach poison against squash bugs.

Figure 8.07

Figure 8.07

Stomach Poison Insects


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Slugs can't resist climbing into this saucer and cover Just plant the unit in the ground so the little saucer rests on the ground. Pour in almost any meal or pellet slug bait and add the top. Can be placed almost anywhere. WALTER F. M1CKE P.O. Box 710 Hudson, MY 12534

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Essential Guide to Organic Gardening

Essential Guide to Organic Gardening

By gardening organically, the dependence on chemicals is removed. By eliminating chemicals used in regular gardening, your vegetables will be healthier because they will get the nutrients by natural means. Unlike traditional gardening; organic gardening will help to prevent potentially harmful toxins from entering your body. Lastly, it is much more environmentally friendly.

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  • Reiss
    Where to buy predatory bugs in Merced, Ca.?
    9 years ago
  • natan
    Are net winged beetles harmful to my vegtable garden?
    8 years ago
  • isumbras
    Where to buy preditor lady bugs and praying mantis sacramento 95831?
    7 years ago
  • Walter Carter
    Where to buy praying mantises in Sacramento Californiaraying mantises in Sacramento?
    7 years ago
    What is a predator of a pelencind wasp?
    5 years ago

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