Grasshopper populations are on the rise in Manitoba as the long-term insect cycle trends toward an increase.
This has combined with other insect-favourable factors such as a warm, open fall to create what may be a good 2009 for the insects and a bad one for farmers.
John Gavloski, a provincial government entomologist, has worked with agrologists, farm production advisers and other entomologists to assemble Manitoba’s annual grasshopper forecast.
“It’s looking like we have the potential for a pretty rough year if the spring conditions are right,” said the Carman-based Gavloski.
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He said the grasshopper population rises and falls in cycles and it is the weather that usually dictates how high and low those peaks and valleys are.
Knowing the level of risk for this pest helps producers plan their crops and seeding practices.
“If you know there is going to be a problem, you can avoid planting highly susceptible crops (such as lentils) in areas where there will be greatest potential for high populations,” he said.
Farmers can also budget for spring labour needs to roll out a monitoring plan once spring arrives.
Entomologists say in any given year severe grasshopper outbreaks can occur, but these are usually isolated unless there is an overall trend toward higher populations.
“That’s what we have this year. And it was combined with good August and fall egg laying conditions due to the warm, dry weather. If we have a warm, dry spring we will have the conditions for a severe infestation,” he said.
The last severe years began building in 2001 and 2002 with a peak in 2003. By 2005, the populations had fallen off. Since 2007, the numbers have been increasing once again.
The Manitoba survey of egg laying grasshoppers takes place at 247 sites during August.
“This is the second year in a row we have seen an increase in the population.
“We have good data for the past decade and it really shows us what lies in store for next year,” he said.
Twenty-three of the sites examined fell into the moderate risk category, while 13 have the potential for a severe outbreak. Three were in the very severe zone.
“The worst is the southwest. But there are large areas that fall into moderate risk,” said Gavloski.
If the weather is warm and dry in May and June, most of the grain growing and pastured areas of the province will be facing a grasshopper problem.
In the area southwest of Melita, grasshoppers will likely be a problem no matter what the weather is like in the spring. North and south of Virden and east of Brandon and Neepawa there are trouble spots, as well as near Carman and along the American border west of Highway 75. East of that highway, south of Winnipeg and along the Red River Valley there are moderate risks. Only in the Interlake and west of Lake Manitoba is there likely to be a very low risk.
“Those areas were wet this summer,” said the entomologist.
The warm fall experienced on the Prairies this year allowed grasshopper embryonic development to continue longer than normal.
Gavloski said the result will be earlier than normal hatching in the spring and increased potential for damage to young crops.
Winter temperatures can play into survivability for grasshopper eggs, but in most cases this doesn’t translate into lower overall populations.
The four species of grasshoppers that are considered crop pests in Western Canada are adept at laying their eggs in areas where snow will accumulate in all but the most severe winter droughts.
“We need temperatures of -15 C at a depth of five centimetres below the soil’s surface to kill the eggs. That doesn’t happen in ditches, field edges and under crop litter,” he said.
“Farmers need to monitor their ditches and other areas where the grasshoppers overwinter well. We’ll only know in the spring, but this is one insect to watch carefully for in 2009.”
