It could be a bad year for grasshoppers in some pockets of Manitoba.
John Gavloski of Manitoba Agriculture says that under the right weather conditions the high egg populations that were found in the 267 August surveys in Manitoba have the potential to produce more than 12 grasshoppers per sq. metre.
Provincial entomologists are meeting in Saskatoon in the last week of January.
“We are hoping to have a tri-provincial forecast and map out, covering the Prairies, some time after that,” Gavloski said.
He said grasshopper damage is difficult to predict because of its relationship with weather and cropping conditions.
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Researchers in Western Canada have suggested that research funding has not met the needs of producers and has resulted in challenges for entomologists making predictions and agrologists providing control and scouting advice.
“It has been an area of agriculture that hasn’t gotten the funding it deserves, considering the economic losses that grasshoppers create,” Gavloski said.
Calculating economic threshold populations is not a straightforward calculation due to variable returns from various crops.
“I am just finishing a formula that calculates soybean aphids (treatment threshold levels). I can do that because we have done the research on the aphids and know what each one can cost. I can’t do that for grasshoppers … and we’ve been dealing with grasshoppers a lot longer … and they are a bigger problem overall.”
Grasshopper economic thresholds in a cereal crop are typically eight to 12 per sq. metre, but in lentils two grasshoppers are considered too many. As farm commodity prices rise the cost of damage done by individual insects rises along with them, dropping the threshold numbers that dictate when it starts to pay to spray.
“Really, with grasshoppers the methods we have been using are based on experienced scientists making their best guesses,” Gavloski said.
Entomologists recommend producers begin watching for grasshoppers as they become easily visible in late May and early June.
Surges in grasshopper populations develop when a few years of weather favourable to the insects occur in a row.
Researchers compare August grasshopper counts to those done in previous years to determine whether an increasing or decreasing trend is taking place. The counts over the past three or four years have increased in many areas of the Prairies.
Good snow cover in winter enhances egg survival, and grasshoppers tend to lay eggs in ditches, fence lines, tree lines and heavy stubble, which attract and hold snow even in low snow cover years.
Extreme cold will damage eggs, but Environment Canada says winter temperatures are rising.
Warm fall weather also improves grasshopper populations, while spring and summer days that are warm and dry tend to significantly increase populations.
Conditions in Manitoba have been near ideal for increased populations. In 2007 daily maximum temperatures in that province were slightly below normal for August and above for September, extending the egg laying period.
Rainfall was below normal for most regions of the province.
Light infestations of four to eight grasshoppers per sq. metre are expected in many areas, but in the Red River Valley, north of Portage la Prairie, near Austin and west of Riding Mountain National Park there is potential for moderate to severe populations between eight and 24 grasshoppers per sq. metre.
Infestations that might meet economic thresholds for cereals in Saskatchewan are expected north of Regina near the Quill Lakes region, south of Regina near Assiniboia, near Rosetown and north of Lloydminster. Cooler conditions in many areas have reduced overall risk, however, like Manitoba populations, they are increasing and warm dry spring weather could create significant populations quickly.
In Alberta the cool conditions during the growing season and a wet early fall season have lowered the risk of large infestations in 2008. An exception to this is the extreme southern area where drought has increased the risk for 2008.
