Spring 2010

Field Notes

The white flowers of pyrethrum, a relative of the chrysanthemum flower, produce a widely used natural insecticide. William D. Bachman/Photo Researchers, Inc.

After growing pyrethrum, a relative of the chrysanthemum flower, on the island of Tasmania for about a decade, Botanical Resources Australia ran into a serious problem in 1999, when a fungal pathogen began ravaging the crop.

“The disease was having a pretty dramatic effect initially,” says Paul Esker, an assistant professor of plant pathology. “It was the sort of situation where if we couldn’t get a handle on it, the industry would really suffer.”

Esker, who specializes in epidemiology and statistics, joined an international team that set out to protect Tasmania’s pyrethrum industry. Also grown in Kenya, the flower is cultivated for a suite of insecticidal compounds, which are the basis for the most widely used natural insecticide in the United States.

Over a number of years, the research team monitored the course of the disease in the fields and experimented with the timing and frequency of various fungicidal sprays. “It was pretty much a case of classic epidemiology,” says Esker. “Everything was new, so we learned everything we could about the temporal and spatial dynamics of the disease. We just tackled all the new questions.”

From there the team developed crop management recommendations to control the disease. The guidelines specified when to spray and when not to, depending on the extent of disease progression, giving growers decision-making tools that would help them keep fungicide applications to an absolute minimum without sacrificing yields.

“The company went from having a substantial challenge,” says Esker, “to being able to handle it. The company is in a pretty good situation now. They’ve even expanded production into Victoria, Australia.”

This work is very similar to what Esker, who holds both research and extension appointments at UW-Madison, does closer to home. In Wisconsin, Esker focuses on field crops—including corn, soybean, wheat and alfalfa—developing pesticide management recommendations that take into account all the key factors that could affect yields.

“My goal, more or less, is to combat the ‘see it, spray it’ mentality,” says Esker. “I’m trying to develop tools that will help growers make better crop management decisions that are based on good, grounded research.”

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