Insects are like the commodity markets. It’s really easy to know what they’re going to do, once they’ve already done it.
One of agriculture’s big challenges is dealing with different insects in different geographies, and doing the best you can to hedge your bets. Like the markets, however, insects are subject to a fair bit of detailed analysis, and every year the entomologists from the three Prairie provinces meet at the Western Pest Forum to present their version of the year that was, and to get a handle on the year that might be.
There are a number of factors that come together to make insects behave the way they do. Weather is one of the big ones, and the insects’ reproductive ability is another. The right number of egg layers surrounded by the right food and enjoying the right weather is a recipe for a perfect storm. When it all comes together, that’s when you get a plague.
On the other hand, you can also get a population crash, even when everything looks like it’s breaking in the insects’ favour. For instance, with grasshoppers, a well-timed rainfall could make the difference between a quiet year and an explosion.
“Well-timed is when the grasshoppers are first emerging,” says Alberta’s Scott Meers. “Raindrops are like little bombs on them, so they get bombarded by rain. Now I don’t think a raindrop would kill them directly, but it makes it cool and damp and they become susceptible to predation, starvation and diseases. If they’re not feeding regularly, which they can’t do when it’s wet and cold, they tend to die off.”
Wet and cold were last spring’s operative words for the Prairies, with melting, drying and seeding all behind schedule. Grasshoppers prefer a warm, dry spring, so 2014 should not have been a grasshopper year. Yet in some places on the eastern Prairies, grasshoppers were a major story.
“It was an interesting year, not what I would call ideal,” says Manitoba’s John Gavloski. “I think there were a lot of eggs in the ground from the previous summer because they had good egg-laying conditions. We got a decent hatch so there was a lot of edge spraying going on. Certainly some fields were sprayed.”
Gavloski also attributes the greater numbers to warmer and drier weather later in the summer.
Hoppers have been building for a couple of years, so they could be headed for some kind of a peak if conditions line up. If Manitoba farmers have a dry spring this year, they may want to keep an eye on their ditches and be ready.
Scott Meers in Alberta agrees, and he advises farmers that grasshoppers may not be gearing up for an explosion on par with 2002 but they could be on the upswing and farmers should watch for larger hatches in the spring.
In Saskatchewan, however, Scott Hartley isn’t calling for big numbers. Last summer’s wet conditions kept hopper populations down over most of the province except for some areas around Maple Creek, off toward the river and west of the sand hills where there was some spraying. But cutworms were another story.
“After a three-year decline, we were expecting it to continue in 2014 but actually it went the other way,” Hartley says. “Early on, cutworms were probably one of the biggest issues. Maybe not as big as four years ago but it still surged much over what it was in 2013.”
Mixed cutworm threat
As with many of our pest species, cutworms aren’t easy to predict and any of several things can affect their numbers. As if that’s not bad enough, there are upwards of five different species.
Cutworms also like to live within the soil, which makes them harder to find and monitor. In fact, sometimes the only real sign that cutworms are a threat is actual crop damage.
“Whether or not they were a huge issue, it was certainly bigger than the year before, so it’s one that we’ll want producers to keep an eye out for in 2015,” Hartley says.
“Cutworms are regulated by natural enemies and particularly by diseases in Manitoba,” Gavloski adds. “The population goes through these cycles and we’re at that peak where we’ve got some higher populations. Sometimes we’ll get a few bad years in a row and populations drop and stay low for a few years and swing back up.”
The weevil risk
“Our cutworm numbers were actually down in 2014, but we really don’t know what that means year-to-year since cutworms are such a hit-and-miss thing,” says Alberta’s Scott Meers. “I expect that we’re still going to have trouble with pea leaf weevil and cabbage seed pod weevil in our traditional areas south of Highway 1.”
In its larval stage the pea leaf weevil feeds on the roots and root nodules of legumes while the adults feed on the leaves. It’s a relative newcomer and was first found in southern Alberta in 2002. It’s particularly fond of fababeans and this could be a serious problem with the growing popularity of faba. It’s a prodigious egg layer with individual females laying up to 1,500 eggs in the soil.
“We’re seeing pea leaf weevil as a problem primarily in southwest Saskatchewan, although it has shown some damage north of the South Saskatchewan River,” Hartley says. “It’s still primarily south of the river and east of the Alberta border to Swift Current.”
Hartley suggests if you had trouble with pea leaf weevil last year you may want to consider a seed treatment for this year. He also suggests looking for its cousin, the cabbage seed pod weevil.
“2013 was a banner year for cabbage seed pod weevil and it’s showing up at a latitude level with Kindersley and Outlook,” Hartley says. “It is north of the South Saskatchewan River now and it’s also well east of Regina. It’s still primarily in the southern regions and not quite to the Manitoba border yet but it’s now into the traditional canola-growing area.”
The seed pod weevil arrived in Canada in the 1930s and is a pest on canola, mustard and the cole crops like broccoli and cabbage. The adults emerge from the leaf litter in the spring and find their way to a plant where they feed on the floral buds and young seed pods. They lay their eggs on the pods where the larva continue feeding on the seeds. They cut their way out and drop into the soil where they pupate. They mature in August, emerge from the soil and overwinter in leaf litter.
Flea beetles and midge
Another canola pest, the flea beetle was not a big problem over most of the Prairies except in Manitoba. Flea beetles don’t like a cool wet spring but they still caused trouble in the eastern plains. It could be a result of the plants emerging slowly and remaining cool for a long period of time.
“That creates problems because the seed treatments eventually wear off and people are out doing foliar sprays in addition to seed treatments,” Gavloski says. “The plants had a hard time getting to that point where they were big enough to resist the flea beetles. The numbers were quite high so if we get a cool, wet spring again then flea beetles would probably be another one to watch.”
Flea beetles are a perennial problem in canola just as wheat midge is a perennial problem in wheat. Alberta and Saskatchewan both had trouble with wheat midge. In Alberta it was the Peace Region that was hardest hit.
“There was substantial damage in 2013 and in our soil survey the numbers were very, very high,” Meers says. “We’re still processing our samples from our fall survey. For the Peace it looks like the risk is going to be lower going into 2015, but we have had some individual sites that are fairly high in central Alberta so we may have midge issues we’ll have to watch in central Alberta.”
“It’s sort of our perennial pest in wheat and certainly the wheat midge forecast map had indicated that there was going to be a lot on the eastern side of Saskatchewan,” Hartley says. “Every year, midge is a problem somewhere in the province although we’ve got increased acreage of midge-tolerant wheat planted.
Those were the big insect problems encountered by Prairie farmers this year. Others that may be worth looking for include Bertha armyworm, diamond back moth and lygus bug. Farmers may also see the detailed reports from the Western Pest Forum at its website.