What’s going to ‘bug’ you in 2020?

Western bean cutworm is quickly climbing the ranks as our biggest threat

Insect pests never seem to get the respect they deserve. If they present a threat during a growing season, they move front and centre, but more often they’re a much lower concern than fertility, weeds and diseases.

Some of that is thanks to today’s improved genetics and commercial varieties and hybrids that produce their hardier, more durable plant stands. Some, too, is thanks to the improved efficacy in available chemical products.

But even so, certain pests are becoming consistent threats with an impact that stretches beyond isolated pockets in one part of the province or another.

According to Dave Curry, crop input representative with Lakeside Feed and Grain Limited, Western bean cutworm (WBC) now leads that pack across much of southern Ontario, and it is also showing signs of expanding its reach farther east. In the past couple of years, Curry has tried setting out more traps to monitor flight patterns and to time their arrival in Ontario fields. But he concedes it’s difficult to find egg masses, and so is trying to determine the best timing to pull the trigger and spray for a pest.

Scouting hard-to-find egg masses continues to challenge even the most highly trained agronomists.
photo: Courtesy Tracey Baute, OMAFRA

“In the 2019 growing season, cutworm wasn’t as big a deal but in previous seasons, we had come across quite a bit more in scouting,” says Curry. “A lot of farmers were seeing WBC and not just in the hot-spot zones around Bothwell or Strathroy: it also seemed to be creeping onto the clay soils, as well.”

The good news on WBC is that grower awareness seems to be pretty solid, says Curry, adding that he believes most farmers have sat through at least one presentation on the dangers it can pose. That includes the connection between cutworm and its ability to open a corn plant to infection from mould diseases like gibberella ear rot (GER).

“If you polled most farmers, they’re going to say that a worm chewing on an ear of corn can lead to mould,” says Curry. “They recognize it as a potential vector but it’s not your typical vector of a virus, not like a piercing insect that’s going to transmit a mosaic virus throughout a soybean crop. In corn, it’s opening up the wound.”

Evidence mounts that Western bean cutworm damage exposes the crop to gibberella ear rot (GER).
photo: Courtesy Leanne Freitag, Syngenta Canada

It’s a point of frustration that in spite of doing the best job of fertilizing and managing weeds in a corn crop using the latest, most disease-resistant hybrid, it’s still possible to have that crop affected by cutworm and an associated disease outbreak.

Heading East

Just as Curry states, WBC is a growing issue in eastern parts of Ontario, a point confirmed by Chris Olbach of Corteva Agriscience. As part of a provincial effort to monitor WBC activity, Olbach has helped track the pest, studying its physiology and behavioural patterns. He’s noticed that cutworm can be damaging to a corn crop one year and a non-issue the next. The good news is that newer traits such as Corteva’s Optimum Leptra or Agrisure Viptera from Syngenta are providing growers better options for control.

“Integrated pest management of WBC is incredibly complex, and knowing this, we’re also very interested in control methods that are efficient and effective where the pest is becoming an issue,” says Olbach, an agronomist with Corteva. “In particular, we wanted to look at how marketability was being significantly affected or where there were significant ramifications from the pest.”

Western bean cutworm has become more widespread across much of Ontario.
photo: Courtesy Tracey Baute, OMAFRA

Olbach echoes Curry’s linking of GER to the cutworm’s presence, noting the mould is associated with the production of deoxynivalenol (DON), which in turn affects the quality and acceptability of a harvested crop. He also notes that European corn borer (ECB) made a slight comeback in parts of eastern Ontario in 2019, mostly with the increase in acreage of non-GMO corn hybrids, a regional trend that has developed in the past several years with a local processor.

On the soybean side

In soybean fields, Curry has become concerned with the number of bean leaf beetles he saw in 2019, which he believes was higher than in previous years. In many instances, it involved fields that had not had an insecticide applied, only a fungicide.

“In a few fields, it was significant enough that the grower likely should have gone in with a control,” adds Curry. “We had some pockets this past year with some drought issues so maybe some farmers had given up on their crop. Then it came to harvest and there were some pretty decent yields, so they may have wished they’d gone in and controlled them.”

According to Dave Curry, soybean aphids could make a return to fields at some point in the next few years.
photo: Courtesy Tracey Baute, OMAFRA

Another surprising find was a visible preference among bean leaf beetles for particular varieties. Curry knows of growers with different varieties of soybeans side-by-side: one would be rife with bean leaf beetle while the other was virtually untouched. Bean leaf beetle is also more of a concern in the IP-food grade market, because it can hurt the appearance of some finished products.

Other candidates for increased monitoring include stinkbugs and Japanese beetles, although both are more of a nuisance than a confirmed yield-robbing pest. Curry agrees that both are on the rise yet it’s rare that a grower will try to control Japanese beetle because they have to be “hit hard” with an insecticide, often with dosages higher than what’s registered.

“In terms of bug pressure, we’re going to run into an aphid year one of these years,” Curry predicts. “It’s been a few seasons since we’ve had widespread aphids — and surprisingly because of the lack of neonics, we were thinking across the industry that we’d have large numbers of aphids. But I wouldn’t be surprised if 2020 is an aphid year.”

Although they can be numerous, Japanese beetles are usually more unsightly than damaging.
photo: Supplied

Olbach also acknowledges the presence of pests that can have an impact on the appearance of the crop but tend to have little impact on yield.

“Flea beetles, Japanese beetles and a few others are examples of very high threshold insects that have not been front of mind in terms of impact from an IPM standpoint,” says Olbach. “Another one we’re usually concerned with, especially with the forage situation, is the potato leaf hopper that migrates in with summer weather patterns.”

Back in southern Ontario, Curry also cites potato leaf hopper but adds that it’s the edible bean sector where it’s the focal point. At some point in the near future, there is concern that the Pest Management Regulatory Agency (PMRA) may discontinue the exemption on CruiserMaxx (thiamethoxam) seed treatments to control leaf hopper. He estimates that it’s currently in use on virtually all edible bean acres in southern Ontario.

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“The nervousness is that potato leaf hopper is a big problem in edibles and they tend to jump on those fields early in the season,” says Curry. “If you don’t get that systemic activity of Cruiser to limit that early flush, it’s going to mean spraying an insecticide on tiny beans and potentially wiping out any beneficial insects, and that’s a big negative for the industry.”

Something new?

Another phenomenon that’s emerged in edible beans that may cross the lines between insect pest and a vectored virus is something loosely called “funky bean syndrome.”

These are patches of green bean pods that are somewhat deformed and never seem to dry down. Both the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and Ridgetown Campus of University of Guelph have done trialling on it and the belief is that it’s some kind of virus. They’re not sure if it’s coming in from insect pests acting as a vector, but its incidence seems to be increasing and Curry has noticed it not just in cranberry beans but also in kidney beans.

Says Curry: “In those patches, there was little in the way of marketable crop and overall, it affected the quality of the beans, as well.”

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