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Grasshopper Threat Low In Manitoba This Year

Last year’s cool, wet summer handed Manitoba farmers one benefit: a low probability of high grasshopper counts this year.

MAFRI’s 2011 grasshopper forecast map shows only a few areas of the province where grasshopper egg counts even register on the scale.

Those areas include the Red River Valley, the northwest region around Dauphin and a pocket in southwest Manitoba where the average density of hopper eggs is very light or even lighter.

Otherwise, egg counts last fall were so low the map shows no potential infestations at all.

Cool, wet weather during last year’s growing season kept grasshoppers from laying as many eggs as they would under hot, dry conditions in which they thrive, said MAFRI entomologist John Gavloski.

But that doesn’t mean Manitoba will be grasshopper free this year, Gavloski is quick to point out.

“We’re never grasshopper free,” Gavloski said. “Even in years when it’s light to very light, there’s still grasshoppers around. They’re just not likely to be at economic levels.”

The last year grasshoppers were a problem in Manitoba was 2003 when there were “quite a few economical populations,” said Gavloski.

But egg counts tailed off in 2004, which was cool and wet. A series of wet summers since then have kept populations down with a few occasional small spikes, he said.

Grasshoppers tend to lay their eggs along roadsides and in ditches, from which the insects can migrate into fields after they hatch.

When the growing season is wet, standing water in ditches and on fields suppress grasshopper populations.

Gavolski said grasshopper eggs themselves are quite resistant to water. Even if submersed for a week, they’ll still hatch in late May and early June.

But nymphs, when they emerge, cannot survive in excessively wet conditions, he said.

MAFRI’s 2011 grasshopper forecast is posted at: cast11.writeup. pdf.

Manitoba has conducted grasshopper surveys since 1931. The current forecast is based on grasshopper counts in August which estimate the egg-laying population.

The forecast also takes weather and recent trends in grasshopper populations into consideration. [email protected]




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