Better pest controls mean safer potatoes

University research is helping state potato growers dramatically reduce the chemicals they use to manage what traditionally has been a pesticide-intensive crop.

The research should lead to further reductions in pesticide use, adoption of less toxic compounds, and greater reliance on cultural practices and biologically based methods to keep pest populations in check, say researchers in the College of Agricultural and Life Sciences.

“Growers in Wisconsin already use the most advanced pest-management methods of growers in any state,” says entomologist Jeffrey Wyman. “We want to help them take pest management to a new level.”

The work has already begun to pay dividends. Growers have reduced the fungicides they applied, thanks in part to Walt Stevenson, a plant pathologist who’s researched Quadris, a new fungicide that is less toxic and used in much smaller amounts than previous compounds. Stevenson’s studies helped accelerate approval of Quadris by the U.S. Environmental Protection Agency.

The passage of the Food Quality Protection Act – which calls for the review and possible elimination of many chemicals now used on potatoes and other crops – prompted Stevenson, Wyman and their colleagues to rethink how Wisconsin growers could remain competitive in this changing regulatory environment.

“Our current methods have two weaknesses,” Wyman says. “First, we manage pests on a field-by-field basis. That’s not realistic because pests operate regionally. Secondly, we remain too dependent on pesticides. We react to pest outbreaks by killing pests where they appear, when we should be using biological control and cultural strategies to reduce pest populations before they become a problem.”

The goals of the new research effort include reducing the need for insecticides, using biological control where possible, replacing high-risk pesticides with reduced-risk alternatives, reducing the amount of pesticides applied, and minimizing the development of pesticide-resistant diseases and insects.

To reach these goals, the researchers must have much more information about pests and their enemies, both within individual fields and regionally. That means increased monitoring both of the pests and their enemies.

For example, there are three major insect pests in potatoes, according to Wyman. “We have to manage each while protecting and encouraging populations of beneficial organisms that can help control those pests,” he says. “And we need to do this not just in individual potato fields, but regionally with other crops and where crops aren’t grown.”

Last year, Wyman and Stevenson began evaluating new ways to improve pest management near Coloma, on 20 fields covering 2,500 acres. The program each week monitored all pests on a five-acre grid in each field. That level of pest scouting is twice as intensive as growers now use.

To maintain, analyze and display the information, the researchers turned to sophisticated computer and graphic systems. The systems transform the information on pests into maps that allow growers to view fluctuations in pest populations across the fields through time. This information greatly enhances the ability of growers to predict pest problems and deal with them effectively if they arise.

Stevenson and Wyman also are evaluating reduced-risk pesticides and use of biological controls. Early results are encouraging, but the low-risk treatments cost more than conventional methods.