Adopt resistance management to save potato insecticides

11/23/2011 08:55:00 AM
By Renee Stern, Contributing Editor

colorado potato beetleClemson University; bugwood.orgThe Colorado potato beetle has an ability to overcome most insecticides.The Colorado potato beetle is a survival expert, developing resistance to just about every pesticide growers adopt.

Even the neonicotinoids that provided an astonishingly long 16-year respite are now showing signs of weakness.

But while neonicotinoid resistance is an industrywide concern, the situation isn’t dire—yet. Careful pesticide rotations and a return to more management-intensive practices should help keep the pest in check.

Among pests worldwide, only the diamondback moth tops Colorado potato beetle in its ability to generate pesticide resistance, says Russ Groves, Extension vegetable specialist at the University of Wisconsin in Madison. “So [neonicotinoid resistance] is no surprise.”

Act now to slow resistance

Resistance can appear with unsettling speed.

Long Island’s beetle populations, for instance, are notorious, sometimes showing signs of resistance in the same year a chemical is introduced, he says. Imidacloprid managed to retain effectiveness for about four years there.

But full-blown neonicotinoid resistance is still intermittent, with well over half the country’s potato growers continuing successful use, Groves says.

Season-long control is diminishing, however. A single application at planting once provided 100 days of control, Groves says.

“Now we’re doing well to get 50.”

“It’s still manageable,” says Mark Otto, president of Agri-Business Consultants Inc., a Lansing, Mich., company specializing in potato management. A third of his clients have fought serious neonicotinoid resistance since 2004.

This past season he sprayed 50 percent more acres, which he suspects is due less to jumps in resistance than to the season’s weather delays.

But the incidents popped up in new areas, sounding warnings for the future.

Zsofia Szendrei, assistant professor of entomology at Michigan State University in East Lansing, has taken over the 12-year national bioassay on Colorado potato beetles. Counts of resistance show up as an exponentially increasing curve, but in 2007 it climbed steeply.

“We’re not back to the days of flaming fields or manually removing beetles,” Szendrei says.

Other pesticides and practices can fill in the gap.

“Neonicotinoids have been around so long growers have gotten into the habit of applying it once,” at planting, she says. “They’ve never had to apply foliar sprays.”

Take an integrated approach

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