Research reduces need for pesticides in cranberry growing

For the fourth straight year, Wisconsin will lead the nation with a cranberry harvest forecast at 2.4 million barrels of the tart, native fruit. From Tomah to Manitowish Waters the colorful harvest means income and jobs. Cranberries are the state’s most valuable fruit crop, with the 1997 crop valued at $162 million.

Wisconsin is using the latest research and technology to produce the crop while minimizing harm to the environment. Most cranberries are grown near wetlands where pesticides can threaten fish and wildlife. Yet unless growers control pests, they can reduce cranberry yields by as much as 80 percent.

Concern about chemical use prompted more than a decade of research by UW- Madison scientists. “We’ve found new ways and new tools to control pests,” says Dan Mahr, an extension entomologist in the College of Agricultural and Life Sciences.

Mahr and co-workers in the Departments of Horticulture and Plant Pathology have produced a computer program that gives growers rapid access to all the latest information on managing the crop. The Wisconsin research incorporated in the program helps growers manage pests with far fewer chemicals than they once used.

“I can foresee a day when cranberry growers control virtually all insect pests with 10 percent to 25 percent of the insecticide used historically,” says Mahr, who works with fruit growers across the state. “Even this small amount will only be used in certain years when other methods have failed.”

With the program – called Cranberry Crop Manager or CCM for short – growers enter and track records on weather, pest monitoring and pest control applications. When they encounter pests, growers can check a CCM section that holds an encyclopedia of information about cranberry pests, including photos and recommendations for controlling 70 weeds, 12 insects, and five diseases.

CCM’s predictive features raise it above other management tools. CCM tells growers when to look for problems and presents alternative control measures for the crop’s most serious pests.

“CCM lets growers anticipate events and plan a program that integrates decisions,” says horticulturist Teryl Roper. “It brings together the research and tells growers the positive and negative consequences of decisions they are considering.”

The program marks a dramatic step forward. For decades, little was known about cranberry pests except what chemicals would kill them. Growers applied pesticides at set calendar intervals.

In 1986, CALS and the Cooperate Extension Service launched a five-year effort to develop an integrated pest management (IPM) program for cranberries. The IPM program emphasized checking for pests — called monitoring or scouting — and applying pesticides only when pest populations were likely to damage the crop.