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MAKING A HOME FOR BENEFICIAL INSECTS

Invite then to your fields, and be sure they stay awhile.

Wisconsin vegetable grower Richard de Wilde isn't satisfied with just releasing ladybugs and other pesteating insects. He's working on ways to invite them in--and keep them around all year long.

"My spring cover crops are a big insectary,' de Wilde says. He first realized that about five years ago when greenchopping hairy vetch. In vetch. sweetclover. red clover--you name it--I saw a cloud of insects moving ahead of the chopper. After a little investigating he figured out that they were beneficial wasps.

Sine then de Wilde has made a commitment to providing food and shelter for his beneficials, He's put up hedgerows; planted flowers. bushes and shrubs; altered his management of cover crops to favor beneficials; and even built 30 birdhouses. His reward: Pest problems have decreased markedly, An extra bonus is the pleasure of insect- and bird-watching walks with his 3-year-old son. Ari,

In fields around the country, farmers and researchers are creating beneficial habitats--havens for insects and wildlife that in many ways resemble pre-agricultural landscapes. Designing a habitat may meats seeding a few strips of buckwheat in a corn field or it may take de Wilde's route--making shelterbelts out of field borders planting cover crops in traffic lanes and generally doing he can to make his farm a home for beneficials

But balancing bugs isn't easy. One plant you choose for habitat could harbor pests. Another may repel desirable insects rather than draw them closer. Researchers studying the complex interactions among insects and plants have no clear-cut answers on what habitat works best. Because some insects move quickly, scientists even have a difficulty providing that habitats control pests. But growers such as de Wilde believe what they see.

When cabbageworm moths were laying eggs in his cole crops a few ears ago, de Wilde thought he would have to spray Bt. "But all the beneficials from the hairy vetch next to my crops tool; care of the problem. Later, less than a week after I chopped the vetch, I had worm problems."

That experience prompted de Wilde to do two things: change his mowing practices and build a more permanent habitat for his beneficials.

Now, he mows less frequently and just low enough to take off the seedheads. He only mows on sunny, dry days when beneficials have the best chance to get out of the way. He's even considering putting a reel on the front of his mower to warn the bugs to flee. He's hoping that one day he'll be able to guide the movement of his beneficials from field to field.

To shelter beneficials after cover crops are gone, de Wilde began establishing 8-foot-wide hedgerows on field borders. When his habitat is complete, he hopes to have a hedgerow every 60 feet.

The hedgerows have an understory of grass mixes such as creeping fescue and annual- or perennial ryegrass with a row of shrubs and a row of flowers. Depending on shrub selection, the hedgerows cost 34 to 88 cents per foot, including maintenance and depreciation over 10 years.

De Wilde chooses the Brasses based on their hardiness and reputation for quick establishment. He looks for flowers and shrubs that bloom throughout the season to provide a regular source of nectar and pollen. The flowers also need a good shelf life, so he can market them with his vegetables. Some tiff his choices: Black-eyed Susan, purple coneflowers, daisies, dogwoods and curry willow. (See sidebar Picking The Whiners" on page 30)

De Wilde wants to prove scientifically that beneficials from his habitat make a big difference in controlling pests. He applied for a grant from the Wisconsin Department of Agriculture, Trade and Consumer Protection to help demonstrate that-his plant selection is on target; measure how far insects travel in search of food; and catalog the classes of beneficials on his farm.

In the meantime. he'll have to settle for the pat on the back he got from a university scientist who visited last summer. "The entomologist must have told me a dozen times, 'I've never seen so many ladybugs."' crop consultant Dr. Bill Becker, Springfield, III., shares de Wilde's zeal for attracting--rather than buying--beneficial bugs. Becker heard about using green lacewings to control European corn borer, but thought releases would do little good if the lacewings didn't have any nectar or pollen for feed.

Instead of buying lacewings, Becker asked some of his clients to plant a 66 foot-wide area of buckwheat--what he calls a "honeymoon strip"--in the middle of a cornfield. Not surprisingly, he found lacewing eggs on the corn.

Corn treated with humic acid in the fields with buckwheat averaged 3 bushels more per acre than untreated corn. Humic-acid corn rows nearest the buckwheat yielded up to 11 bushels more.

Based on the data, Becker recommends that his clients plant one 15 foot-wide buckwheat strip every 440 feet. He figures strips will cost about $6.50 each on a field one-quarter mile long and require little maintenance. He's banking on the buckwheat's rank growth to hold down weeds. After it develops mature seed, his clients mow it. It reseeds and starts flowering again in time for second-generation corn borers.

Copyright 1993 The New Farm.


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