By Greg Booth

Research supported by AURI’s Pesticide Reduction Options program is giving fruit and vegetable producers good reasons to cut down on farm chemicals.

In August, producers got one more incentive: the EPA banned or restricted the use of two widely used organophosphates: methyl parathion and azinphos methyl. Residue from these pesticides can harm children, studies have shown. At the same time, USDA is encouraging integrated pest management practices; the goal is to have IPM in use on 75 percent of U.S. cropland by next year.

AURI recently awarded up to $30,000 in matching funds to each of six new PRO projects “that look promising to reduce the use of pesticides,” says program manager Edward Wene, AURI microbiologist in Crookston. Up to $200,000 per year is invested in PRO, funded in part by a pesticide tax.

Current projects are checking into the most effective ways to reduce or eliminate pesticides in beans, corn and strawberries. Innovative methods include spray timing, wool mulch and plant spacing. In some cases, farmers are finding that methods given up by the mainstream years ago — mechanical cultivation and weed burning, for example — are actually inexpensive and effective. The most effectual tool, say researchers and farmers, is management — closely monitoring crops and pests.

Reducing pesticide use can save growers time and money. “There’s definitely an economic incentive to spray the least amount possible,” says William Hutchison, principal researcher for an IPM study on snap beans.

Stamp out borers in beans

The European corn borer is one of the most common pests in the 6,000 acres of snap beans grown in Minnesota. To get rid of it, timing is everything, says Hutchison, a University of Minnesota entomologist. In test plots at the Rosemount Agricultural Experiment Station south of the Twin Cities, he’s looking for the best spraying times to obtain “the minimum number of applications — two or three sprays versus four to six.”

“One of the big challenges for growers is the timing issue,” Hutchison says. “For the European corn borer, it’s when the eggs are laid.”

Hutchison is also exploring which of the 10 most commonly planted green beans have the best inherent resistance to corn borers and which are most susceptible.

Chiquita Foods in Owatonna, Minn., a large snap bean grower, is cooperating on the project. At harvest time, Hutchison collected data on infestation levels. “The major concern with green beans for the processing industry is the presence of damaged pods, larvae in the pods, or larval contaminants,” Hutchison says. “Their tolerances are near zero.” One or two worms in a two-ton truckload, he says, can be disastrous.

Clean up the corn rows

Letting farmers call the shots was one way Elizabeth Dyck learned about how effective cultivating corn can be in reducing herbicides.

“We had several sessions where we worked with farmers and the Coteau Ridge Sustainable Farming Association,” says Dyck, U of M assistant agronomy professor at the Southwest Research and Outreach Center in Lamberton, Minn. “The farmers insisted we include the spike tooth harrow treatment. Cost is very important, and everybody has an old spike tooth harrow sitting around.”

Dyck’s trials study the effect of five cultivation techniques for corn: rotary hoe, flex tine weeder, spike tooth harrow, flame weeder and row crop cultivator. Working closely with Madison, Minn. farmer Carmen Fernholz, she’s ascertaining when and how often growers need to cultivate. While many farmers cultivate on a regular schedule, Dyck says, “now we’re looking at the stage of the weed to determine hoeing.” Fernholz’s farm offers a large plot where real-life techniques and problems can be studied.

Participant Kent Olson of the U of M’s applied economics department will help growers like Fernholz judge the relative profitability of methods such as flame weeding. “In the early ’60s, propane (weeding) was pushed by the propane industry,” Dyck says. While some farmers adopted the technique, it’s still new to many.

Dyck says effectual cultivation depends on management. “As you move away from high chemical inputs, the time you spend on management increases. You substitute management skills for input.”

“We stand behind the fact that cultivation is very effective,” Dyck says. “You can either reduce greatly or eliminate herbicides if you take a stance with cultivation.” Both organic farmers and those just looking to reduce herbicide costs will benefit from the research, she says.

The research is “very labor intensive ... before and after every (cultivation) pass, we take a weed count so we know exactly how much weed mortality there is,” Dyck says, “So far, most of the treatments look viable. The timing of the cultivation seems to be more important than the method.”

De-worm the cabbage patch

Cabbage gets lots of insecticide for a crop grown only on about 1,000 acres in Minnesota. Up to seven or eight applications a season are sprayed on a typical patch, Hutchison says.

Using integrated pest management, Hutchison is working with farmer Gary Paul of Apple Valley, Minn. to reduce that to three or four. Cabbage looper is the most damaging cabbage pest in Minnesota, Hutchison says. Others include the cabbage worm and the diamondback moth. Most cabbage and other cole crops are grown near the Twin Cities for wholesale to grocers and processors.

“Several pyrethroids are labeled for cabbage,” Hutchison says, “but they wipe out the beneficial insects. That tends to create aphid problems.” In a previous PRO project, Hutchison found that the insecticide Spintor controlled cabbage looper while being “soft on beneficials.” This year, “we made spray decisions based on the thresholds we’ve worked out. We went in with two applications of Spintor, alternated with one or two Warrior (insecticide) sprays. That’s our IPM program.” Traps are used to see when moths are entering fields. Using thresholds — based on the number of moths caught in traps — to decide when to spray eliminates “counting every worm on every plant.”

Damage in unsprayed control plots is compared with sprayed plots. The study also looks at beneficial insects, crop yield and marketability. “The preliminary (trial) was very promising, so we wanted two years,” Hutchison says.

Dress berries in sheep’s clothing

Faced with a dwindling number of herbicide options — and problems engendered by the continuous use of chemicals — fruit and vegetable producers are looking for new methods to control weeds. A project headed by Frank Forcella of the USDA-ARS is using mats made from low-quality Minnesota wool for a biodegradable, breathable weed barrier in strawberries. He’s also testing canola mulch for its natural ability to inhibit weed seed germination.

The wool mats, canola and combinations of the two were used in strawberry field trials this summer at the North Central Soil Conservation Research Lab in Morris, Minn.

Talk about pests in sweet corn

Most sweet corn growers know there are more effective ways to control pests than by the calendar, but where can they get timely information about pest monitoring and control?

Jeanne Cibrowski, integrated pest management coordinator for the Minnesota Department of Agriculture, wants to improve communication and education to help farmers control sweet corn pests. Her PRO project aims to provide farmers with up-to-the-minute information about pest pressures, chemical and non-chemical control options, and other information for sustainable production.

Cibrowski’s project includes monitoring, electronic communication for growers, and field days to get information to farmers. Her model could be useful for other vegetable crops as well.

Minnesota is the nation’s second largest producer of sweet corn. In 1997, sweet corn with a value of $59 million was grown on 127,200 Minnesota acres.

Put weeds in the shade

In sweet corn fields, defeating giant foxtail and wild proso-millet might be better accomplished with planting techniques than with herbicides. Corn is vulnerable to herbicide injury, and not many herbicide options are available.

A two-year study by Roger Becker of the U of M’s agronomy and plant genetics department and the Minnesota Fruit and Vegetable Growers Association is testing variables such as planting date, row spacing and corn varieties on weed pressures.