By BRIAN LEAHY
of The Gazette
While other farming sectors have increased their reliance on pesticides, potato growers have reduced chemical inputs by 37 percent since 1996, industry officials said during the annual Central Wisconsin Potato Grower Field Day Tuesday at the Hancock Agricultural Research Station.
"Those are very significant numbers you should all be very proud of," said Mike Carter, government affairs director for the Wisconsin Potato Vegetable Growers Association.
The reduction is part of a collaborative effort between the WPVGA, the World Wildlife Federation and the University of Wisconsin. The goal is to keep reducing chemical use, Carter said. It shows the potato industry's concern for the environment and worker safety.
Entering into the partnership also gives growers increased market opportunities and advantages as they work towards getting an ecological label on their products, he said.
Fifteen growers have signed up for a test program to increase their use of bio-intensive integrated pest management practices, said the program's coordinator, former Portage County UW-Extension agent Deanna Sexson. All of those growers will get a voice in the development of the ecological label.
Researchers are continuing to look for new and safer pesticides to replace older, high-risk chemicals, said UW-Madison entomologist Jeff Wyman.
"Obviously we can't reduce the use of those materials if we don't have something equally effective and as equally economic to replace them," Wyman said.
Growers have a variety of threats to their crop, ranging from insects like the Colorado potato beetle to diseases like late blight.
Late blight lesions showed up as early as Monday, July 10, this year, compared to July 22 last year, said plant pathologist Walt Stevenson. This year's earlier appearance is a concern.
"Virtually in every field you can find some late blight somewhere," Stevenson said.
To fight late blight, growers must spray fungicides. Depending upon moisture and temperature conditions, the chemical application may offer a window of protection that could last from anywhere from around five to 10 days. When the window is up, growers must spray again.
Researchers are looking at developing strains of potato more resistant to late blight.
"Our goal is to have commercially acceptable varieties with high levels of resistance so we can dramatically reduce spraying," Stevenson said.
Another problem facing growers is soil compaction, which can cause standing water in fields, hinder root penetration and prevent gas movement, said Dick Wolkowski of the UW-Madison Department of Soil Science. The restrictive layer can be caused by natural hardpan or be induced by human activity, especially wheel-traffic compaction from farm equipment. On medium textured soils, soil compaction can cause a 15-50 percent yield loss.
Growers can either wait for natural processes, like freezing and thawing, or till a couple of inches deeper than the restrictive layer to lessen the soil compaction, Wolkowski said.
"Generally, natural processes are going to take a long time," Wolkowski said.
One researcher in Minnesota was able to identify a wagon trail used 100 years ago because the ruts were still there, Wolkowski said.
On deep tillage plots, researchers have been tilling 12-14 inches deep, Wolkowski said. Soil inversion is a concern with tilling deep. Subsoil and stones can be brought to the surface, while crop residue left behind in conservation tillage practices can be buried.