Winter wheat seedlings make a tasty snack for mature grasshoppers looking for a fall meal.
As a result, producers looking to plant their winter wheat or fall rye crops this week or next should be concerned about the potential losses.
In Montana and South Dakota, where the grasshopper infestation is as serious as that of the Canadian Prairies, state agronomists suggest delaying planting until as late as Sept. 25. But Canadian experts suggest the week of Sept. 15 is as late as practical for more northerly climates.
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Dan Johnson of Agriculture Canada in Lethbridge said the producers should take the grasshopper threat seriously.
“We never know exactly how much damage they will do. We could recommend producers seed later and the weather could keep the crop from growing enough before freeze up and that would be bad. We could tell producers to ignore the grasshoppers because they won’t do that much damage, that happens some years, and they will gnaw it to the ground. You never know,” said Johnson.
Scott Hartley, a Saskatchewan entomologist, said he has received calls from producers saying they have already lost fall crops to grasshoppers.
“A guy called to say that his fall rye crop had attracted all of the local grasshoppers from the brown neighbouring fields to his green crop. He now says he has the best looking piece of summerfallow in the district.”
Johnson said grasshoppers might be partial to new green shoots.
Agronomists suggest that producers manage their fall-seeded crops by monitoring grasshopper problems daily and spot spraying or spreading poisoned bran baits.
Hartley said many sprays are ineffective because they rely on the grasshopper eating the plant material and “most of a two-leaf cereal field is dirt when you spray it. That means using the highest rates of spray and still it might not be enough.”
Johnson said spot spraying should be done with an insecticide that works on contact with the grasshoppers and at the highest recommended rates.
“A malathion or a Decis at the higher rates. Remember these aren’t small insects like we spray in the spring. These are the big mature ones,” he said.
Hartley said bran baits spread over a field might be the best defence.
“Economically it is the most effective,” he said.
The Americans have another arsenal, not available to Canadian producers, systemic seed treatment using Helix or Gaucho.
Johnson said the strategy can work, but it requires high levels of seed treatment and isn’t legal in Canada.
Montana agronomists recommend treating the seed used on the outer rounds of the field with Gaucho.
Canadian entomologists suggest this may not be effective because of the low rates placed on seed and because the insects are distributed across the entire field in the fall.
