If producers were hoping for a break on flea beetles and grasshoppers this year, they didn’t get it.
Both made the highlight reel for the most serious pest damage in the province, according to a seasonal summary released by Manitoba Agriculture and Resource Development in early November.
In both cases, it’s a continuation of a multi-year trend that has seen pressure for those pest species on the rise.
Why it matters: Pest pressure can carry over from season to season, making a seasonal summary a valuable tool.
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Flea beetle populations have been “chronically high” in the last few years, according to provincial entomologist John Gavloski.
“At this point, there’s really no hint of that trend going down,” he said.
Producers reported that seed treatments — the go-to first line of defence for flea beetles — were not making the cut this spring. Feeding damage delayed crops already stressed by spring conditions, while some areas reported stem feeding.
Foliar control became a common theme in patches across the province, both on field edges and full-field application. Some producers had to jump into the sprayer cab as many as four times, the summary noted.
Reseeding was reported in the northwest, Interlake and eastern Manitoba. In early June, an estimate out of eastern Manitoba suggested that 10 to 15 per cent of canola acres had been resown.
The issue also was not limited to the spring. Agronomists and farmers noted late-season flea beetle feeding on podded canola, leading to yet more foliar insecticide passes in August.
Part of the issue, Gavloski said, might just be the sheer amount of canola available for flea beetles to munch.
The Manitoba Agricultural Services Corporation (MASC) reported over 3.37 million acres of canola last year.
There has been predation and parasitism, Gavloski noted, “although not to the point where growers can ease up… they definitely have to still be on their guards for flea beetles.”
No dice with Mother Nature
Weather was also stacking the odds against canola this spring.
Dry soil and wildly fluctuating temperatures stalled growth and ran out the seed treatment clock, since flea beetle management relies heavily on the hopes of growing canola past its vulnerable stage before the effective treatment window runs out.
“Really, the key is getting the plants to the point where they have at least three or four true leaves quickly,” Gavloski said.
If germination is slow or if crops stall at the early-seedling stage, as seen in some fields this year, flea beetle risk goes up.
In addition, plants were shocked by a wild see-saw of temperatures in the early season, with forecasts swinging from frost warnings to significant heat in the space of a week.
“When you look at that type of stress on the crop, you can’t lay blame on the plant, the seed treatment, nothing,” Justine Cornelsen, agronomist with the Canola Council of Canada said. “Mother Nature just threw the biggest curveball at canola… ”
No-win scenario
It is often the early-seeded canola hit hardest in recent years, Cornelsen noted, leaving some producers to push seeding back in the hopes of better conditions and quicker growth. Some producers opted for that strategy this spring.
“The strategy of seeding a bit later into a bit warmer soil and, if possible, into moisture, some years that can work quite successfully,” Gavloski said. “What didn’t happen this year was the soil moisture part.
“The growers were doing all the right things, but they didn’t get co-operation from the weather,” he added.
In contrast to the trend in recent years, however, Cornelsen noted that early-seeded canola this year might have been further along and better able to handle the extreme temperature swing.
Seed treatments were also less effective this year, Cornelsen noted. Products require water to move through the plant, she said, and there was little available.
“There was a lot of blame placed on seed treatments this year,” she said. “where, in all reality, it was like you were growing an untreated variety, just based on the conditions. The treatments just were not able to be taken up into the plant to be useful.”
Considering Manitoba’s recent history with flea beetles, Gavloski urged producers to scout and, on top of seed treatments, “anticipate that, at least in some years, a foliar insecticide application may be needed… ”
Grasshoppers
Grasshoppers, likewise, have been on the rise in recent years.
Some canola fields also saw spraying for grasshoppers from mid-June to late August this year, sometimes linked to the pests moving in from nearby forage land.
The pests were noted in a range of crop fields this year, ranging from flax to dry beans, soybeans and hemp.
Perhaps the most talked about damage, however, came from forages. Livestock producers noted worrying levels of grasshopper damage in hayfields and pastures, not least of which because drought had made grazing and hay in short supply in many of those same areas.
“It’s a combination of a couple of things happening,” Gavloski said. “One, the grasshopper populations have been climbing the last few years, and that’s partially because of the hot, dry summers we’ve been having.”
Under those conditions, grasshoppers are also left with less naturally occurring food in places like ditches, increasing the incentive to feed on crops, Gavloski noted.
Drought-stressed crops also have limited ability to compensate for feeding damage, he said.
Management
Gavloski urged producers to keep a sharp eye out for pest grasshoppers next year starting in early June.
Field edges are typically hot spots for those insects, he said, or “anywhere where there was a lot of lush, green vegetation in August and September the previous season.”
“That’s often where you get the higher hatch occurring,” he said.
In some cases, control may only be needed at the field edge, while other fields may have a more uniform population through the field.
Producers dealing with grasshoppers in a pasture, meanwhile, might want to consider laying down insecticide in strips. Gavloski pointed to research out of the University of Wyoming, which indicates that strip treatment gave almost as much control, and much less cost, of spraying the whole pasture.
As well as grasshoppers and flea beetles, the province saw some patches of diamondback moth, alfalfa weevil and aphids, among others, the pest summary noted.
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