PESTICIDE REDUCTION OPTIONS

Plant genetics may be the key to significant pesticide reduction in certain crop systems. Developing varieties that resist disease and hamper weed growth is the crux of two PRO projects spearheaded by University of Minnesota researchers.

Rooting out the bean rot

PRO researchers are developing kidney bean varieties resistant to root rot, says Richard Meronuk, a plant pathologist at the U of M. The varieties are one way to help growers reduce chemical use in beans.

Root rot saps nutrients and water-absorbing capacity from bean plants, leaving stunted plants that are more susceptible to drought. "It's one of the most serious things affecting kidney bean yield," Meronuk says.

Working with Northarvest Bean Growers Association, Ken Grafton at North Dakota State University and the Staples Ag Center, Meronuk, Jim Percich and graduate assistant Consuelo Estevez de Jensen have identified three organisms that attack kidney beans. They're evaluating both biological and chemical treatments by testing beans planted in infested soil at the Staples Ag Center.

"We're looking at resistance with biological controls, chemical controls and a combination of those," Meronuk says. "If we're as successful as we have been in some other lines, I think we can put together a series of biological controls. We'll have a good start in two years; to develop a good variety takes four to seven years."

Canola combats the pressure

Killing the weeds without killing canola is the goal of William Lueschen's PRO project. With canola, a profitable oil seed crop, "just about any weed can be competitive," says Lueschen, a U of M agronomist.

Weeds like foxtail, pigweed, smartweed and wild buckwheat not only reduce yields but also contaminate the canola seed, Lueschen says, making the grower's crop worth less. By developing varieties that shade out weeds early and tolerate herbicides, his PRO research will allow growers to reduce chemical use and harvest a cleaner crop.

Three different canola varieties, identified in the first phase of the project, were planted this spring in Roseau County in northwestern Minnesota. "These more competitive varieties close the canopy faster for better weed control," Lueschen says. Seeding rates of 6, 12 and 18 plants per square foot will help researchers determine the optimum plant density for weed control.

Lueschen says the summer trials will also assess differing herbicide applications. One treatment will use no herbicide, one will use a half-rate application of a grass herbicide, one will use half the rate of broadleaf herbicides, and one will use a full array of grass and broadleaf herbicides.

Currently, few herbicides are labeled for use on canola. Growers can use Treflan, Poast and Assure II. "We're hoping to get a Section 18 (special local use) for Herbicide 273 and Stinger," Lueschen says.

Other studies will combine preemergent herbicides with three canola varieties, and postemergent treatments with eight varieties to evaluate canola tolerance to herbicides. Lueschen is working with county extension educators in northwest Minnesota, Erv Oelke with U of M agronomy and plant genetics, technicians Dave LeGare and Erik Levorson, and the Minnesota Canola Council.

Canola is "a small acreage crop, and companies don't really want to come in and spend a lot of money to develop a weed management program," Lueschen says. "If it weren't for support from AURI, we would not have the funding to do this trial. There are very few herbicides that are labeled for canola, and this is the time to do this kind of work. Farmers are going to be more likely to adopt alternate weed management practices, including selecting varieties that are more competitive, higher seeding rates, and carefully timed planting dates.

"It's our thesis that if we plant competitive canola varieties, there is an opportunity to reduce herbicides."

Researchers are developing canola varieties that will shade out weeds early, requiring less chemical and producing a cleaner crop. The inset photo reveals a standard canola canopy, planted on the same day as the fast-growing variety to reveal the dramatic difference the canopy can make controlling weeds.