Growing Beneficial Insects

green lacewing, predator of insect pests

green lacewing, predator of insect pests

There are few people like Everett “Deke” Dietrick. If there were more like him, insect pests would cease to be a problem on Earth.
It would be a gross understatement to categorize Dietrick’s understanding of insects as profound. Dietrick knows insects the way an author knows the characters in his books or a mom knows her kids.
Dietrick’s specialty is biological insect control, the pest-management strategy that utilizes predaceous and parasitic insects to keep populations of insect pests at bay. Forty-five years ago, Dietrick started the world’s first commercial insectary, or insect farm, in his garage. Insectaries grow large quantities of beneficial insects that feed on insect pests.
Dietrick raises lacewings and parasitic wasps in Ventura and sells them to commercial and backyard farmers. The process involves several stages. To mass-rear beneficial Trichogramma wasps, which are used on such pests as the European cabbage worm, Sitotroga moths first must be raised. With their hind- end ovipositors, the wasps – which are smaller than pinheads – pierce the moth eggs and deposit their own eggs within. The larvae that hatch out of the wasp eggs eat out the insides of the moth eggs, after which the wasp larvae pupate and emerge as adult wasps that will continue to oviposit in more moth eggs.
Lacewings – half-inch long creatures with light green bodies and diaphanous wings – are the indestructible workhorses of insect biological control. They have proved resistant to every pesticide and are effective at controlling most caterpillar pests. Most beneficial insects, including ladybugs, are killed when pesticides are applied. When a ladybug chews on a pesticide-laden aphid, the pesticide passes into the ladybug’s body. However, since lacewings suck the juices out of insects, rather than chewing on their
exterior shells, which are more highly concentrated in applied pesticides, they are better able to survive pesticides.
You don’t have to purchase beneficial insects to bring them into your garden. Lacewings lay their eggs on bottle trees (Brachychiton populneus) and California lilac (Ceanothus spp.). Parasitic wasps visit gardens where yarrow and common fennel are found. Among the best plants to grow for attracting beneficial insects are grasses, whether Sudan grass, ornamental grasses or cereal grasses such as corn.
It is always a pleasure to talk to someone who speaks the truth and debunks popular myths; Deke Dietrick is such a person. Conventional horticultural wisdom holds that tomatoes and corn should not be planted together, since the caterpillars that feast on corn also will eat up a tomato crop. Yet Dietrick has found that if corn is planted around tomatoes, beneficial insects – such as lacewings – will be attracted to the corn and curtail caterpillar development.
Dietrick also took exception to the current method for dealing with the Mediterranean fruit fly. Millions of irradiated, sterile fruit flies – shipped in from fly farms in Guatemala – are released in Los Angeles County each week; any fertile flies that are living in this area will not produce offspring after mating with a sterile fly. Dietrick maintains that to more effectively combat this pest, natural insect predators of the Medfly should be imported
from the Cameroons region of Africa, which is the Medfly’s original home.
When Dietrick first got involved in biological insect control, pesticides were not yet widely used in agriculture, and the government was a big sponsor of biological control projects, especially in California. After World War II, with the advent of powerful pesticides such as DDT, it was thought that all insect pests soon would be eradicated, and there was no need to continue with biological methods. Chemists displaced entomologists as the leading authorities on insect control.
It soon was discovered, though, that no pesticide could completely eliminate an insect pest. Resistant populations developed that created the need for other pesticides, a spiral that has continued to the present day. In recent years, as pesticide application costs have skyrocketed, farmers have begun to return to biological control.

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