Grasshoppers pose threat

Drought, plague, fire and pestilence.

It seems like hard-luck farmers in Western Canada have seen a little bit of everything this year.

Now, you can add grasshopper damage to the growing list of concerns that has drought-stricken growers shaking their heads in disbelief.

According to the Prairie Pest Monitoring Network (PPMN), adult grasshopper numbers are higher than normal across all three prairie provinces for this time of year.

Conditions are favourable for rapid insect development and increased egg-laying activity, which could lead to even bigger problems next year.

Above average temperatures in late June and July caused a noticeable increase in grasshopper development, PPMN said in its July 22 update on grasshoppers.

Feeding activity has already affected crops in many parts of the West. And in most cases, the optimal timing for chemical control has already passed.

In its weekly pest report dated July 14, PPMN said most of the Melanoplus sanguinipes (M. sang) grasshopper population was expected to be in the fourth or fifth instar stages.

A week later, as of July 21, populations were predicted to be 35 percent in the fifth instar stage and 35 percent in the adult stage, based on model simulations.

By comparison, long-term average values for this point in the growing season are 11 percent in the fifth instar stage and less than two percent in the adult stage.

Meghan Vankosky, an entomology expert with Agriculture Canada, said adult grasshopper populations were patchy across most of Western Canada last week.

But adult development was well advanced, raising concerns about feeding damage on traditionally vulnerable crops such as cereals, as well as other crops, including canola.

As crops dry down in the heat or are cut and salvaged for feed, adult grasshoppers will fly to the next available feed source.

“There are some places where we’re seeing a lot more grasshoppers) than other places…. Development is quite advanced this year compared to a normal year,” Vankosky told The Western Producer on July 22.

“With all the heat that we’ve had… we’re seeing grasshoppers in the adult stage already, and normally we wouldn’t be seeing quite so many adults for another week or two.”

The timing of of adult grasshopper development is important for a few reasons.

For starters, adult hoppers are larger and more voracious feeders. Crop damage can occur quickly if populations are high.

“The adults can do more damage because they’re bigger,” Vankosky said.

“The later instars — the fourth and fifth instars — they’re going to be doing a lot of feeding damage right now too … because they’re getting ready to molt into those adult stages.”

Dispersion is another important factor.

Because the wings of adult hoppers are fully developed, the insects can fly greater distances in search of food. Adults can move quickly from crop to crop as feed sources disappear or are exhausted.

The ability to fly, combined with their size, also makes adult hoppers harder to control chemically.

In Manitoba, chemical control efforts were taking place in many areas last week, according to Manitoba Agriculture’s July 21 pest update.

“Grasshoppers continue to be a concern in many areas with some control occurring along field edges or whole fields,” the report said.

Manitoba Agriculture is receiving reports of non-traditional hopper species such as clear-winged grasshoppers and Packard grasshoppers, which are typically less common that the two-striped variety.

Vankosky said the timing for chemical controls has probably passed in most areas.

“We’re really past that optimal time for management,” she said.

“It’s really best to be scouting for grasshoppers early in the season, when the nymphs are young and less able to disperse.”

Attempts to control adults chemically may have disappointing results because controlling adult insects requires a greater dose of chemical and adults can simply fly away from sprayed areas and resume feeding elsewhere.

With crop yields expected to be low across much of the West this year and commodity prices expected to remain high, the economic threshold for chemical control is likely to be lower this year and the urge to control hoppers in the adult stage might be greater than ever.

For those reasons, later-than-optimal spraying activity could be more common.

A third important factor associated with high adult populations is mating activity and egg-laying.

“It’s those adults that are laying eggs and it’s those eggs that are going to (potentially contribute to) a grasshopper outbreak next year,” Vankosky said.

“The earlier those adults are active and mating, the more eggs they can lay so we might see even more grasshoppers next year because of that.”

Entomologists across the West are monitoring grasshopper numbers and development and are also assessing insects to determine which grasshopper species are most dominant this year.

In Saskatchewan, field staff plan to conduct a grasshopper species composition survey to see which species of grasshoppers are most active. Population surveys will take place in all three prairie provinces.

Information gathered will be used to assess the grasshopper threat entering next year.

“If we stay in a drought cycle, conditions are really optimal for grasshopper development,” Vankosky said.

“But I think it’s also important to remember that we can see pretty quick changes in grasshopper populations and outbreak potential if the weather changes,” she added.

“If we see a switch from hot and dry to more cool and wet conditions through the rest of the summer, that could reduce grasshopper egg laying activity, and if it’s cool and wet next spring, that will also help to reduce grasshopper populations.

“So even though things look a little bit dire right now, that can change quickly if the weather changes.”

For more content related to drought management visit The Dry Times, where you can find a collection of stories from our family of publications as well as links to external resources to support your decisions through these difficult times.

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