Manitoba’s provincial entomologist is confident grasshoppers won’t be a problem in the province this year.
Rainy weather last August and September made it difficult for grasshoppers to lay eggs, which means fewer of them should emerge from eggs this spring.
“We had a lower population to start with and they didn’t get great egg laying conditions (in 2010), so we’re at a lower point in the grasshopper cycle,” said John Gavloski.
In his annual summary of insect populations on the Manitoba Agriculture website, Gavloski said no grasshopper problems were reported in wheat, oats and barley crops in Manitoba last year. As well, 2010 was a poor year for most insects that feed on crops because wet weather kept them at bay.
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Parts of the province were extremely wet, such as Winnipeg, which came within one millimetre of setting a new record for total precipitation in a year.
However, what made 2010 exceptional was that every part of the province was wetter than usual.
“Over the whole growing season, throughout the province, (precipitation) ranged from about 160 to 200 percent of normal,” said Manitoba Agriculture meteorologist Andy Nadler.
“In a typical year, we have certain areas that are wet and certain areas that are dry,” he said.
“I don’t know of any area in southern Manitoba that was drier than normal (in 2010).”
Despite the wet year, there are several insects that growers need to keep an eye on in 2011.
Cutworms
Gavloski is expecting another year or two of higher cutworm populations, which have been high for several years in the province.
The two species of primary concern are the red-backed cutworm and the dingy cutworm, which damaged a number of canola fields in central, northwestern and southwestern Manitoba last year.
However, Gavloski expects cutworm numbers to drop in a couple of years because populations of cutworm predators and parasites should increase, keeping the insect in check.
“They are regulated by parasites, so usually when you get a few years (of high populations), the parasites will catch up and moderate things.”
Bertha armyworm
Last year’s moth counts for bertha armyworms indicated the insect wasn’t a problem in most parts of Manitoba, with the exception of trap counts in Benito, where they exceeded 400 during a week in early July.
Diamondback moth
Diamondback moths forced several producers in eastern Manitoba to spray canola fields last year. Trap counts were highest in Landmark and Dugald, where diamondback moths exceeded 100 per week.
However, Gavloski said it’s difficult to predict if they will cause problems this year because they blow in with the wind from the United States.
Flea beetles
Beetles could emerge as a significant pest if canola is slow to develop and the weather is warm and dry.
“Populations aren’t as high now as they were a few years ago, but they’re one to keep an eye on,” Gavloski said.
Outbreaks depend on conditions in the spring, but flea beetles caused minimal damage to canola crops last year. Spraying was necessary only in the Swan River region.
Soybean aphids
Aphid populations increased from late July into August, but there were no reports of the insect reaching economic thresholds in 2010.
Nonetheless, populations of 100 aphids per plant were found around Beausejour.
Like diamondback moths, it’s difficult to predict soybean aphid numbers because they blow in from the U.S.
Although soybean acreage in the province topped 500,000 last year, it’s unlikely the aphids could survive a Manitoba winter because a U.S. study found the insect couldn’t overwinter in the northern parts of Minnesota.
