The tiny, grey weevil was the greatest pest problem of the 2025 growing season, said Manitoba Agriculture entomologist John Gavloski.

“My poor summer students this year [found] 1,739 weevils in our 27 fields,” Gavloski told an audience at the 2026 Manitoba Ag Days in Brandon in January. “They were over double the economic threshold.”

WHY IT MATTERS: After a few years of minimal presence in Manitoba, cabbage seed pod weevil populations boomed in Manitoba in 2025 — in one case to twice the economic threshold.

Cabbage seed pod weevil is a three- to four-millimetre insect that lays its eggs inside young canola pods where its larvae feed on seeds. It overwinters as an adult under leaf debris and moves into flowering canola fields in late June and early July.

Gavloski’s survey results showed a dramatic population boom in 2025. In one field north of Carman, the count was as high as 226 weevils in a 25-sweep sample.

The economic threshold for cabbage seed pod weevil damage is 25 to 40 weevils per 10 sweeps, or 63 to 100 in the 25-sweep samples Gavloski’s survey uses. That Carman-area field was more than double the economic threshold and was treated once the population was confirmed.

Prior to 2025, the highest single-sample count Gavloski had recorded in his surveys was six weevils.

The pest has also been spreading eastward across the province. While populations were historically confined to southwestern Manitoba, weevils were detected as far east as the Ste. Anne area in 2025.

Scouting the critical first step

The weevil arrived in Manitoba from Alberta, where it had spread after an introduction to southern British Columbia in the 1930s. By 2017, it was first detected in Manitoba near Morden.

Survey counts remained very low for years before last season’s surge.

“We went from low counts to really high counts in the Carman area, going from 2024 to 2025,” Gavloski said.

“So bottom line, watch your fields. Start learning how to scout your fields.”

Scouting is complicated by the weevil’s defence mechanism: when disturbed, it drops to the ground and plays dead. Finding a three-to-four-millimetre grey insect on bare soil is no easy task.

“Just walking the field without a net, you could have a lot of them there and really not know it,” Gavloski said.

He recommends producers use a sweep net and conduct 10 sets of 10 sweeps: five near the field edge, five farther inside, during the flowering period in late June and early July.

Research from Alberta suggests that trap cropping (seeding the outside rows of a field one to two weeks earlier than the main crop, then spraying only those edges) can concentrate weevil populations and provide effective control while protecting pollinators in the main field.

Seeding date is another factor. Earlier-seeded canola, which flowers first, attracts significantly more weevils than later-seeded crops.

While cabbage seed pod weevil dominated the conversation, Gavloski noted several other insects that warranted attention across Manitoba during the 2025 season.

Flea beetle damage lessens, cutworms trend down

Flea beetles remained a concern but caused less economic damage than in recent years — largely due to a warm, moist spring.

“I don’t think it was because the flea beetle populations crashed,” Gavloski said. “I think it was because we finally got a season where people seeded the canola, it came up, and it seemed to have enough moisture and enough heat to get you from seedling to three to four leaf stage relatively quickly.”

Cutworms were still present and some fields were treated, but Gavloski said populations appear to be on the downward side of a cycle. He compared cutworm population dynamics to a bell curve: populations build, peak for a few years, then taper off, often driven by natural parasitoid activity. The worst years were 2020 and 2021.

“We’re kind of on that downward curve,” he said. “Populations have dropped off a little bit.”

Western and southwestern Manitoba bertha armyworm hotspots

Bertha armyworm became a regional concern, particularly in the western and southwestern parts of the province around Gladstone, Neepawa, Holland and Brandon. Some activity extended toward the central region.

Traps Gavloski monitors showed many locations crossing into the “uncertain risk” category during the summer. He noted some positive signs, however. There were reports of armyworms found dead on top of plants — a sign that naturally occurring viral and fungal pathogens had gotten into the population.

“If they’re up on the top of the pods in the day and they’re not moving, that’s a good thing. They’ve got pathogens. You want that,” he said.

Diamondback moths of low concern

Diamondback moths stayed relatively quiet in western Manitoba but caused some problems in the eastern part of the province in late summer. Populations are believed to have blown in on winds in late May and early June.

“They don’t overwinter well in the Canadian Prairies,” Gavloski said. “They’re just kind of getting blown in almost randomly on winds, and they get dumped wherever the winds dump them.”

Lygus bugs caused scattered economic-level infestations, primarily in the Interlake, and some fields were treated. Unlike the chewing insects on the list, lygus bugs pierce plant tissue with a beak-like mouthpart, inject enzymes and feed on the juice. They particularly target buds, flowers and young seeds.

On the positive side, Gavloski said that grasshoppers and aphids were largely non-issues across the province in 2025, with very little spraying required for either pest.

“Every year, weather drives things,” Gavloski said. “We get things that go up, we get things that go down.”

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The old battle against potato virus Y (PVY) is becoming harder there, noted Tyler MacKenzie, research and development co-ordinator at the Agricultural Certification Services Lab of Potatoes New Brunswick, and it’s a sneaky problem. Infected plants are hard to spot. With the strains the region is dealing with, there often aren’t a lot of above-ground symptoms to warn of a budding issue.

WHY IT MATTERS: Manitoba Agriculture is on the watch for aphid populations, known vectors for PVY, every year.

PVY remains the top cause of mosaic disease in potatoes, bringing down yields and tainting seed stocks, according to Agriculture and Agri-Food Canada. Growers know it by its common signs: stunted growth, vein banding, leaf drop and early death of plants, with infected potato crops often showing dwarfed size and crinkled leaves.

It’s also an insect management problem. The virus hangs out on the mouthparts of aphids who have fed on infected plants, spreading through a field. It doesn’t take much PVY in a field for seed potatoes to be rejected, resources published by AAFC note.

Necrotic strains like PVYntn have made the problem worse, according to research by MacKenzie and other potato virologists with the Agricultural Certification Services Lab.

These strains cause brownish necrotic rings in tubers while producing minimal leaf symptoms.

Research from potato commodity groups shows that the newer strains of the virus spread faster than older varieties, affecting more plants even when individual impacts were lower. The strains also cause severe tuber necrosis in susceptible varieties.

The problem has grown as New Brunswick’s potato industry consolidated, attendees heard. The number of seed growers has declined, while more operations mix seed production with processing crops.

“In recent years, you can see that the exclusive seed growers … managed to keep their PVY levels low, but the mixed growers really lost control of their PVY,” MacKenzie said.

Why management matters

But the data also showed growers using strict management practices kept infection rates low even during severe aphid years.

The virus can overwinter in tubers left in the field and is easily transmitted during seed cutting operations, or when poor handling causes tissue damage. Aphids, especially the green peach aphid, are the primary mode of transmission. Alternative host plants include other members of the nightshade, goosefoot and legume families.

The most effective control measure is using clean seed.

Fields planted with seed containing around two per cent PVY had five times the failure rate in bad years compared to cleaner seed, MacKenzie said.

Oil sprays as an aphid control also reduced infection rates. Growers applying at least two litres per acre of mineral oil weekly saw infection rates drop by half or a third compared to those using lower concentrations, research showed. Combined with strategic insecticide use and monitoring through aphid alert programs, these tools help growers control the disease, attendees heard.

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If you’re a grower, you’ve likely got pest insects at some level and hopefully at a minimum. As John Gavloski, extension entomologist with Manitoba Agriculture, pointed out at the Crop Diagnostic School last month in Carman, there are particular crop pests to keep a close eye on this year. In this video, Gavloski shares which insects are getting most of the attention in the 2023 growing season and some ‘good news’ for producers on at least one insect front.

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In 2022, pea aphids plagued many Manitoba farmers, said John Gavloski, entomologist with Manitoba Agriculture. Aphids on soybeans also hit economic levels, particularly in the central, east and Interlake regions.

“Some people were caught in a dilemma,” Gavloski told an audience in Clandeboye on Jan. 4.

“They had economic populations but once again they were noticing lots of dead aphids – something called aphid mummies.”

The concept behind aphid mummies could inspire a horror movie, but they actually benefit farmers. Each mummy is the leftover cuticle or husk of an aphid. A tiny, black parasitic wasp walks along the plant, tapping its antennae. When it finds an aphid, it whips its hind-end around and stabs an egg into the aphid.

“That takes just a fraction of a second,” Gavloski said.

The egg hatches, and the larvae eats the aphid from the inside out. As the larvae matures, the aphid dies and becomes “slightly puffy or mummified,” an article from the University of Massachusetts Amherst says.

“It becomes a house for the wasp larva,” said Gavloski.

When the body-snatching wasp reaches adulthood, it chews its way out of the aphid’s corpse and leaves the mummy behind.

Gavloski said farmers asked him if it was possible to spray for aphids without killing the beneficial insects. Until recently, the only available products were for horticulture, he said.

A new field-crop product could change that. Carbine, a flonicamid-based product from FMC, purports to selectively kill aphids, lygus bugs and a few others by affecting their ability to eat. Carbine is targeted for alfalfa, lentils, field peas and other pulses.

Another creepy phenomenon last year signaled trouble for grasshoppers in parts of Manitoba.

While clearwing and two-striped grasshoppers made a sizable appearance, a grasshopper-killing fungus also reared its head.

Gavloski reported sightings of dead grasshoppers clinging en masse to the tops of plants. Clumps of bugs could be found scattered throughout fields. This is called summit disease.

It’s caused by a fatal fungus called Entomophaga grylli. Grasshoppers pick up spores as they hop about in search of food. The fungus infiltrates their body and multiplies in their bloodstream, Gavloski wrote in a November article about the disease.

As the grasshoppers near death, the fungus causes them to climb to the tops of plants and hang on. Then, when the carcass rots, fungal spores drift over a greater area.

Higher incidence of summit disease in 2022 is likely due to the wet spring, because the fungus thrives in moist conditions, Gavloski said.

Other grasshopper predators prevalent in 2022 were bee fly larvae, blister beetles and field crickets. All three eat grasshopper eggs.

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Ag-chemical company FMC has announced that its flonicamid-based insecticide, Carbine, has the stamp of approval from Canadian regulators and will reach the market in 2023.

The Group 29 product “disrupts the potassium channels in the pests’ nervous system,” interfering with the insect’s mouthparts and restricting them from feeding, said a Dec. 13 FMC release.

The product is targeted for use in alfalfa, lentils, field peas and other pulse crops.

As of Dec. 20, Health Canada’s database showed the product as registered, although no label had been uploaded.

Why it matters: The selective insecticide has been pitched as an alternative to broad-spectrum products that kill beneficial insects along with pests.

The addition to Canada’s pest control landscape could be part of integrated pest management programs. The company says the chemical’s activity is specific enough to control aphids, while having “minimal” impact on beneficial insects like pollinators.

The product controls immature and adult aphids, according to FMC Canada. It says Carbine’s residual window will prevent recolonization.

“We are committed to bringing unique, sustainable products to growers as they face significant yield-robbing pests,” said FMC Canada insecticide product manager Frances Boddy, in the release.

Carbine has a one-week pre-harvest window when application is restricted, but can otherwise be used any time in the growing season. FMC Canada urged producers to scout often once crops start to flower and to take economic thresholds into account before using the product.

Aphid fight 2022

Field peas, soybeans and small grains all had aphid problems in the past growing season, according to a summary from Manitoba Agriculture.

Pea fields in central, southwest and northwest Manitoba were sprayed for pea aphids, in some cases mixed with fungicide. Soybeans also saw economically damaging levels of aphid in August, with the Interlake, central and eastern regions reporting control measures.

Provincial entomologist John Gavloski noted a number of broad-spectrum insecticide passes were needed to control the pests, but “in some fields high levels of natural enemies were noted, particularly evidence of parasitism.”

“Having more selective insecticide options is welcome, as a fundamental component of integrated pest management is preserving natural enemies of crop feeding pests. This gives farmers and agronomists the option of controlling aphids that surpasses economic thresholds and doing minimal harm to the natural enemies that are feeding on or parasitizing multiple crop feeding insects.”

Registration

Isk Biosciences Corp. successfully registered Carbine with the Pest Management Regulatory Agency as of Nov. 30. FMC is licensed to market the insecticide, which is trademarked under the Ohio-based agro-chemical firm’s parent company, Ishihara Sangyo Kaisha Ltd. of Japan.

It is the second flonicamid-based insecticide registered by the company. In December 2010, Isk Biosciences Corp. received approval for Beleaf, registered for control of aphids and, in some crops, tarnished plant bugs, other lygus bugs and thrips in horticultural crops, as well as flax, alfalfa, other forage legumes and field legume crops except soybeans. FMC’s insecticide portfolio also includes Beleaf.

The company said Carbine will also reduce lygus bug and tarnished plant bug populations.

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