“I don’t know if anybody in this room experienced rootworm in 2025, but it was a bad, bad rootworm year,” said Jocelyn Smith, an assistant professor in field crop entomology at the University of Guelph’s Ridgetown campus. She was part of a panel on corn rootworm at the 2026 SouthWest Agricultural Conference in Ridgetown.

Why it matters: Corn rootworm has been well-controlled in Ontario since the introduction of Bt traits and more diverse crop rotations, but that is changing with more resistance showing up.

The biggest problem is fields where corn is repeatedly planted, usually using the same trait packages.

“We’ve gotten maybe a little lazy with some of our rootworm management,” Smith said.

The growing season was dry in 2025, which meant more corn rootworm larvae hatched and survived.

“The weather saves us a lot of times on rootworm pressure, but in 2025, it didn’t,” she said.

Resistance is spreading, especially in areas with more livestock, where it’s more likely farmers with limited acres grow corn after corn.

That means there are problems with resistance in Huron and Perth counties, and it’s spread to Middlesex and Lambton, Smith said, with resistance now found in eastern Ontario and Quebec.

Near-continuous corn

In the United States Midwest, a variant of rootworm has shown up that can hang around for a crop rotation out of corn. Smith said that hasn’t been confirmed yet in Ontario.

Canadian growers can feel a bit better compared to their counterparts in the U.S., where many growers only plant corn and soybeans, and corn-on-corn for grain corn is more common.

That means resistance started showing up shortly after the Bt trait arrived, said Erin Hodgson, a field crop extension entomologist at Iowa State University.

Hodgson said there are about 13 million acres of corn in Iowa, but about four million of those acres are in continuous corn, meaning at least three years of corn. Some have been in corn each year for 20 years.

The industry is used to evaluating the damage in Iowa.

For each corn root node that is pruned to within 1.5 inches of the stalk, there’s about a 15 per cent yield loss, she said. Corn rootworm feeds mostly on nodes four, five and six. There’s no rescue treatment once the damage has been done, she said, so prevention is the key.

Back to chemistry

As Bt corns have failed — and in Iowa, they’ve failed across the valuable traits, including multiple resistance to three of the traits — corn growers have been relying more again on soil-applied insecticides. That has included older chemistries such as organophosphates and pyrethroids, but also some new compounds.

Using soil-applied insecticides involves retrofitting planters to hold chemical boxes, and means farmers have to work with highly toxic chemicals.

Research in Iowa by Aaron Gassmann at Iowa State shows that there’s little value to using soil-applied insecticides if Bt traits are working.

There are new RNA interference (RNAi) technologies now available, but they don’t result in immediate effect, as they shut down insect metabolism. Larvae could still feed for a week, therefore it’s difficult to tell if the technology has been effective. The risk of resistance to RNAi is also high, Hodgson said.

Crop rotation in Ontario helps a lot, she said, but encouraged farmers to question whether they need Bt traits in their corn every year, especially if they’re practicing rotations.

If corn only sees a field every three to five years, if the populations aren’t there, corn without Bt could perhaps be planted, she said.

“Rootworm is the easiest insect to control if you want to, if you just play the game right,” Smith said. “It’s got to be corn roots. If there aren’t corn roots there, they will all die.”

Could biocontrols help?

Researchers have known since the 1980s that nematodes can kill rootworm, but the distribution of nematodes to the field level has not worked.

Tuesday Schroeder, a master’s student working with Smith and Dave Hooker at Ridgetown, and a biological innovation manager with Corteva, is looking at ways to improve the application of entomopathogenic nematodes (EPNs) to the field.

The challenge is that “EPNs are really susceptible to environmental conditions. They’ll dry up and die, and they’re not really tolerant to cooler conditions,” said Schroeder.

She said they could be used in conjunction with Bt traits to help increase the longevity of the traits.

The nematodes are washed into a tote and then applied using a sprayer with streamer nozzles at 50 gallons of water per acre.

What is the lifecycle of corn rootworm

Corn rootworm beetles — both the western corn rootworm and northern corn rootworm that exist in Ontario — lay eggs from July to October.

Over the winter, the eggs are “just totally dormant,” says Smith. “They’re pretty indestructible in the soil throughout the winter.”

Tillage doesn’t affect the eggs; neither does freezing weather.

The beetles burrow as deeply as they need to so their eggs are laid into moisture, even to depths of a metre into the soil.

The eggs start hatching in southern Ontario around June 10, feed on roothairs and move through three instar development stages by the middle of July at which time they are large enough to feed on the roots of corn.

This is the point of the most damage, with goosenecking of corn plants indicating a severe infestation.

By late July or early August the rootworm pupate and emerge as adults, ready to start the process again.

The post Ready for corn rootworm resistance? appeared first on Farmtario.

Monitoring for CRW adults using sticky traps is an effective tool for flagging fields that have suspected Bt resistant rootworm populations if placed in fields planted with a CRW Bt hybrid. The traps can also provide insight into what the risk of rootworm injury will be in next year’s corn crop if that field is in continuous corn production. Higher beetle populations this year mean more eggs being laid in the soil that will hatch into larvae next spring.

If sticky traps catch an average of two or more beetles per trap per day or if easier – if after seven days in the field, each of the four traps monitored catch 14 or more beetles – that field is at high risk (Figure 1). If these traps are in a field that was planted with a CRW Bt hybrid, this indicates that a lot of rootworms survived feeding on roots expressing Bt and could be a resistant population. These fields need to be reported to your seed provider and myself to test for potential resistance.

If the field is not planted to a CRW Bt hybrid but will be going into corn again next year, it will need some form of protection at planting, either by using a soil applied insecticide, planting a CRW Bt hybrid or consider rotating that field out of corn next year to avoid rootworm injury. Crop rotation at least once every four years is also a more sustainable management practice to help address resistant rootworm populations. More information on trapping instructions can be found in this Field Crop News Article: https://fieldcropnews.com/2024/06/corn-rootworm-trap-participants-needed/

WESTERN BEAN CUTWORM

Western bean cutworm (WBC) moth flight has begun with a few traps are catching lower levels of moths. Don’t assume low moth counts this early means low risk. With such variable planting dates and growth stages in every region, these early moths may unload a lot of eggs in only a few of the more advanced fields out of desperation. Scouting is advised in the earliest planted fields to check for egg masses. If five per cent of the plants scouted over three scouting periods has egg masses, the field will need an insecticide application. Remember that WBC larvae need at least a tassel developing in the whorl to survive in the absence of an ear of corn, so focus on fields in later growth stages first. Fields younger than V8 are less at risk right now. Later planted fields will be at higher risk when peak moth flight takes place late July to early August. More information on moth counts can be found on the Great Lakes and Maritimes Pest Monitoring Network.

EUROPEAN CORN BORER

With European corn borer (ECB) populations becoming less susceptible to Bt corn, we need to start scouting for unexpected injury in Bt corn.

Eastern Ontario needs to be extra vigilant as they neighbour provinces with known resistant populations but all growers in Ontario should start this practice. Scout between 10 to 20 areas of the field after V6 stage, looking for signs of ECB injury including leaf or whorl feeding, frass and stalk tunneling in the midrib or at the leaf axils (Figure 3), bent or broken stalks and the tell-tale sign broken tassels. Any signs of ECB feeding injury in Bt fields should be reported to your seed provider and myself. Don’t assume the injury you see if on only refuge plants.

To help reduce the spread of resistance, shredding stalks during or shortly after harvest will need to become standard practice again to kill any overwintering ECB larvae in the corn stubble left after harvest. More information on recent resistance detections and signs of ECB injury can be found on the Canadian Corn Pest Coalition Website.

More information on biology and management of any of these pests can also be found on Ontario CropIPM and Crop Protection Hub. As always, critical pest updates will also be available through the rest of the season on Field Crop News.

– Tracey Baute is an entolmologist with OMAFA’s Field Crop Team. This article was originally posted at Field Crop News website.

The post Corn pests to watch over the next month appeared first on Farmtario.

Two years ago, Tracey Baute, field crops entomologist with the Ontario agriculture department, noted that resistance to Bt Cry proteins had become an issue, where three out of four targeting corn rootworm were closely related.

Cry3Bb1, mCry3A and eCry3.1Ab were identified as “cross-resistant”, meaning a population of corn rootworms resistant to one will exhibit the same level of resistance to the other proteins.

Why it matters: Corn rootworm resistance is an increasing problem where corn is grown continuously.

That meant the remaining protein –Cry34/35, while documented as resistant, was not cross-resistant.

Baute maintained it was only a matter of time before the fourth Cry3 protein would also develop cross-resistance, drastically reducing the efficacy of those hybrids with corn rootworm traits.

A year-end 2023 report from the Ontario Corn Rootworm Trap Network shows some of the numbers are not encouraging. In all, 59 trap sites were monitored, and corn rootworm adult activity peaked during different times in August.

The good news is that populations were 60 per cent lower than in 2022. However, 12 of the trap sites reached or eclipsed trap thresholds of two beetles per trap per day. All were in continuous corn, with the exception of one site that was surrounded by fields of continuous corn.

“These sites should be rotated out of corn in 2024 to knock back resistant populations and help to maintain what durability we have left in Bt-RW hybrids,” wrote Baute in the Nov. 9 Field Crops News entry.

In 2019, Huron, Perth and Bruce counties showed the highest corn rootworm resistance. Two years later, there was unexpected damage detected in Middlesex and then Chatham-Kent and some parts of Central Ontario.

From the results of the 2023 trap network, Chatham-Kent and Huron were rated as “high” (2 to 4.9 beetles per trap per day), Middlesex, Oxford and Waterloo were “very high” (5 to 9.9 beetles), and Perth and Wellington fell into the “extreme” category (more than 10 beetles per trap per day).

Similar results

Agronomists and advisors with Bayer Crop Science saw many of the same indicators with corn rootworm. They had a similar number of reported product inquiries for rootworm damage in 2023 as they had in the past few years. But environmental conditions, particularly the heavy rains that marked late June and early July, were thought to be the primary cause of the 60 per cent decrease in number of adults found in traps.

“Last year, we had a favourable winter with dry soils,” says Adam Pfeffer, row crop market development manager for Bayer.

“If we go through a prolonged period of saturated soil conditions this winter, survival may be reduced, but we won’t know until the spring,”

The good news from Pfeffer is that some growers are focusing on a rotational non-host year in fields with a history of multiple corn-on-corn years. Scouting and more education on the benefits of a rotational non-host year are the two key take-home messages for growers.

“Economics have pushed continuous corn in some regions, either to meet demands of their livestock operation or for the positive economic advantage corn brings for grain and oilseed growers,” says Pfeffer.

“But these economic advantages can be reduced quickly if corn rootworm populations grow further and pressure the management tools available, which is why corn rootworm is called the ‘billion-dollar pest’.”

The introduction of Bayer’s SmartStax PRO hybrid line includes the use of RNAi (ribonucleic acid interference) technology that improves performance and durability against corn rootworm. But RNAi is not the lone solution to combat CRW resistance, nor should it be regarded as such. Bayer advocates the pairing of RNAi traits with current Bt/Cry1 rootworm traits already on the market, ensuring reliability and robustness.

“As we talk about these new products, they are one tool in corn rootworm management and we must continue to ensure best management practices, like rotation, for continued success,” says Pfeffer.

“Even with new traits on the market, the key to CRW is managing and lengthening rotations. We do see improved efficacy with three modes of action and we expect longer durability. Rotation to a non-host crop will always be a powerful tool for corn rootworm management, along with scouting and preparing proactively for pest challenges.”

In addition to SmartStax PRO, Bayer is also launching VT4PRO, also with RNAi technology, starting in 2025.

The post By the numbers – corn rootworm in 2023 appeared first on Farmtario.

Now a provincial entomologist says Ontario producers may face the same decision if resistance to the Bacillus thuringiensis (Bt) trait in corn continues to grow. Bt-resistant corn rootworm causes lodging and goose-necking in corn plants, making much of the crop impossible to harvest for silage. 

Tracey Baute, field crop entomologist with the Ontario Ministry of Agriculture, Food and Rural Affairs, encouraged Ontario livestock producers to consider alternatives to corn-on-corn and announced the results from the province’s participation in the Corn Rootworm Adult Monitoring Network during the 2022 Forage Focus webinar series last month. 

Why it matters: Resistance to the Bt control gene is now widespread across the U.S. corn belt and increasingly present in Ontario, to the degree that resistant rootworms are migrating to neighbouring farms.

Baute’s forage and grazing colleague, Christine O’Reilly, said some Ontario silage producers have suffered yield losses of 50 per cent or more with confirmed rootworm damage present.

Baute and O’Reilly, along with Corteva Agriscience’s eastern Canada dairy strategic accounts manager Ashley Knapton, presented their concerns in the webinar hosted by the Ontario Forage Council.

Baute stressed that corn rootworm isn’t a new pest and it is native to North America. The introduction of corn with the Bt gene initially allowed producers to put mitigating management strategies to the backs of their minds and grow corn in the same field year after year.

Resistance has changed that.

[RELATED] Country Guide: A new trait for corn rootworm

Baute said there are four versions of the Bt gene, three of which are closely related, so simply switching from one form of control to another in year-over-year corn isn’t an adequate strategy.

Experience in the U.S. shows that, even with a tight soybean-corn-soybean-corn rotation and a pest that was initially thought to depend solely on corn for larval feeding, at least one species of corn rootworm has adapted to survive.

“They figured out a way to get their eggs into a field that corn is going to come back to the next year,” said Baute. “This is a pest that we need to switch it up and change management tools repeatedly so we don’t have them adapt to what we’re throwing at them.”

The Monitoring Network, which links adult beetle trapping efforts across Canada and the U.S., included 76 Ontario sites in 2022. According to Baute, 57 per cent of those reached the economic threshold of two beetles per trap per day in sites across southwestern, midwestern, central and eastern Ontario.

Sites above the threshold but not reaching nine beetles per day – 28 in all – were in the counties of Elgin, Norfolk, Waterloo, Bruce, Grey, Northumberland, Lennox and Addington, Ottawa, Stormont Dundas and Glengarry, and Prescott and Russell.

[RELATED] Corn Rootworm trapping study will encourage crop rotation

However, 15 fields reached maximums greater than nine beetles per day, with the highest Ontario field reaching 32. These sites, which Baute described as indicating a “high to extreme” risk of the presence of Bt-resistant pests, were in the counties of Durham, Huron, Lambton, Middlesex, Chatham-Kent, Oxford, Perth, Wellington and Hastings.

For all of these counties, “it flags to me that next year, they need a different option for rootworm management and mainly, to rotate.”

She also noted the list includes nine of the top 10 counties for dairy production or feedlots.

“This is actually a direct problem for livestock producers and particularly for dairy production.”

For many livestock producers, rotating to alfalfa is the most obvious alternative. Ideally, costs don’t increase.

“You’re still growing the alfalfa and the corn that you need. You’re just planning better each year about where you’re going to put them,” said O’Reilly.

Alfalfa provides a rotation option

Some producers hesitate to grow alfalfa far away from the barn or silo, added Knapton. But using alfalfa to broaden the crop rotation requires not treating it as a “set and forget kind of crop which, I think, sometimes it can be in our minds.

“It’s so easy. We plant it and then, boom, it’s there whenever we go to cut it. But are we doing everything we can to maximize that production to make sure we’re getting everything we can out of that acre?”

There’s nothing ground-breaking about this, Knapton said. Put enough seed down. Monitor the field to determine the plants and stems per square foot. And “be critical of your aged stands,” even if it looks like there’s still a lot of green.

“Leafhopper can come in and do a tonne of damage before we really recognize it,” she said, encouraging producers to take a good look after a thunderstorm and assess leafhopper activity.

Harvest timing is important. In a dry year, it may be possible to delay harvest to maximize yield and stay within quality requirements.

Apply fertility based on removal rates and pre-crop soil tests, Knapton advised. Alfalfa will probably need phosphorus and potassium. Sulfur and boron deficiencies are also possible. Manure is great but it doesn’t match what’s removed by alfalfa, and ideally should be tested for its nutrient value.

O’Reilly agreed that it’s important to invest in the crop.

“Cheaping out on those inputs might save us something in the short term but, in the long term, that cost per tonne really matters. If we have to drive over that acre every time – three or four times a year – to cut that hay, we might as well make sure we’re doing it for three tonnes per acre rather than one.”

For those unable to add more alfalfa to the rotation, the forage specialist offered other strategies.

A winter cereal followed by a fast-growing summer crop like sorghum or sudangrass could potentially fill a feed bunk. Drawbacks include a small risk of allelopathy with these crops and significantly less energy than corn silage.

Beets, by contrast, are more comparable to corn silage. O’Reilly said they’re not a commonly grown crop in Ontario and do require specialized harvest equipment, but they can be effective in breaking down rootworm resistance and could fit nicely into a dairy or beef ration.

If switching crops isn’t possible, another option is to trade acreage with a cash-cropping neighbour.

O’Reilly noted former Grain Farmers of Ontario chair Mark Brock recently explored this idea through his studies with the Nuffield Scholarship program and encouraged Forage Focus participants to find out more about his findings.

Given that “there really are no other transgenic products coming that can save us from this pest,” Baute stressed that vigilance against Bt resistance remains important.

For those growing Bt corn in counties identified as high-risk or neighbouring counties, “I strongly recommend that you (join the trap monitoring network) next year. The traps are a benefit. Yes, you have to change them once a week for about four weeks – six would be ideal – but it gets you to see what the corn rootworm activity looks like in your field. It gets you more accustomed to ‘is this normal or is this high for this field.’

“While you’re looking, look for those signs of resistance. And what you’re looking for is beetle activity.” If there aren’t already silks or ears on the corn, look for leaf-eating. Look for goose-necking or stunted plants.

“Don’t always assume that it’s because of drought. Stunted plants are often a sign that something is happening at the root level. Dig them up and take a look and see if there’s any root clipping.

“And, of course, if you see lodging after a windstorm, it’s time – in any of these scenarios – for both your seed provider and myself to be notified so we can go in and, if it’s a Bt corn rootworm variety, take and test those beetles and see if you have developed resistance.”

The post Silage growers urged to protect feed supply from Bt-resistant corn rootworm appeared first on Farmtario.

Corn rootworm tops the list, according to Tracey Baute, field crop entomologist for the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). 

Why it matters: Grain growers have limited tools to address spider mites and corn rootworm. Striving to reduce the pests’ opportunity to develop resistance to those tools is critical.

Baute told Farmtario that a lack of active corn rotation is all too common, promoting corn rootworm resistant to Bt hybrids. Some growers with higher resistant populations are relying on RNAi sprays, often on top of the same hybrids that spurred higher resistance pressures in the first place.

In doing so, they are relying on a single mode of action, likely building resistance to Bt hybrids and RNAi controls.

“The biggest, most effective tool is rotation for even one year, so we don’t have to keep moving to different tools every year,” says Baute.

“Rotation is not always simple, that’s the problem, but it is most effective at wiping the rootworm population out so you can use a variety of different tools over the next three years, and not keep exposing the rootworm to the same modes of action.”

Higher corn rootworm pressure results in poorer silage quality, potentially requiring producers to buy additional feed.

“Rotating means you don’t have to use rootworm hybrids the first, maybe even the second year. That is the more sustainable practice. We would see a big difference if growers thought ahead…There really are no other rootworm solutions coming down the pipeline,” says Baute.

Spider mites soak up dry conditions

It’s been a reasonably good year for spider mites too – for the mites, anyway.

Increased rainfall, heavy dews and cooler nights have applied pressure on spider mite populations in most of the province. In drier areas, such as central Ontario and Norfolk county, there are fewer predatory pathogens, which has allowed spider mites to reach concerning levels.

Higher pest populations lead to greater insecticide and miticide application. Though necessary, Baute is concerned at the level of resistance the pest is developing for Cygon and Lagon, the only economical chemical controls available to broad-acreage growers.

Other chemistries from the horticulture sector are available, but per-acre costs are prohibitive for broad acre use.

“We’re in a difficult period where we’re almost holding our breath, hoping we don’t have too many hot dry years and mite problems,” she says. “We were lucky some rains came through that didn’t make every field a problem.”

A little of this, a little of that

Other pests have been noted too.

As in 2021, aphids are a problem for much of Eastern Ontario. The region’s multi-year aphid problem is surprising, says Baute, noting a general absence of beneficial insects is odd. The impact of weather on development of aphid-attacking pathogens may be an additional factor.

Regardless, the need to spray for aphids two or three times a season is not normal, but a reality for some soybean growers.

Western bean cutworm has not been an issue. Baute expects a fair amount of preventive spraying has occurred, and said she hopes applicators managed to time it well.

As Ontario inches closer to harvest, she reminds growers to keep harvest interval requirements in mind.

The post Concerns grow over control-resistant pests appeared first on Farmtario.

The resulting recommendation to producers in midwestern Ontario is to break the cycle by not growing corn. 

Why it matters: Insects like corn rootworm eventually develop resistance to controls, so new traits are needed.

Starting in 2023, a new hybrid will be available containing RNAi technology to complement existing Bt proteins. SmartStax Pro, from Bayer Crop Science, builds on the existing SmartStax trait to provide improved protection against corn rootworm.

Most products available in Canada combine a Cry3 with a Cry34/35 trait and these continue to provide suitable control against corn rootworm in most situations. But if one Cry toxin is effective against corn rootworm, it increases the rate at which resistance evolves to the remaining toxin.

How a hybrid performs will depend on what products were previously used and what agronomic practices were employed, such as crop rotation versus continuous corn.

“We’re seeing more of that in eastern Canada and in areas where there is corn-on-corn, mainly for livestock producers who need that feed,” says David Kikkert, corn and soybean portfolio lead with Bayer Crop Science Canada.

The ribonucleic acid-derived mode of action prevents production of a targeted, life-critical protein in corn rootworm larvae. Without it, they die. The greatest risk is associated with continuous planting of hybrids that have developed resistance to the stacked lines. Combining RNAi with two other Bt toxins is believed to provide the best protection from corn rootworm.

“It’s novel and a different mode of action,” says Kikkert. “It’s also toxic to all of the instars and that’s unique where some of the Bt proteins may have different efficacies with different instars.”

Rootworm is best managed with cultural or rotation plans along with scouting. A SmartStax Pro hybrid with RNA interference is believed to provide the most robust control of corn rootworm. However, it is not a silver bullet.

New signs of trouble

In 2019, Huron, Perth and Bruce counties were hot spots with the greatest corn rootworm resistance. According to Tracey Baute, field crops entomologist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), unexpected damage sites have been identified in Middlesex County, although they’re yet to be confirmed resistant. Populations were also higher in Bt CRW fields in Chatham-Kent and central Ontario in 2021.

“Based on the corn rootworm trap network data, at least 13 sites had concerning levels of adult rootworm activity compared to others in the province,” says Baute. “Without intervention – that is, crop rotation and changes in management practices – these sites will spread to others nearby.”

She agrees that RNAi is another tool for rootworm management and that hybrids from the SmartStax Pro line-up are meant to be paired with Bt hybrids for multiple modes of action to reduce selection for resistance. Yet there are producers who may see this technology as a “bridge” that enables corn-on-corn or continuous corn production.

“In the presence of Bt resistance, relying on RNAi hybrids as the sole management tool results in relying on one mode of action, significantly increasing the risk of resistance to RNAi now,” says Baute.

“We have to follow more sustainable practices and not rely solely on transgenic corn to manage CRW.”

Bt-resistant rootworm puts more strain on a functioning trait, in this case RNAi. Corn rootworm has always found a way to develop resistance to single modes of action or single management tools.

To keep resistance low, rootworm requires rotation of practices, the most effective of which is opting out of corn one in every four years. Baute acknowledges the challenges livestock producers may have in sourcing feed.

“However, if they continue as status quo and resistance becomes widespread, they’ll lose significant yield and feed anyway. Those costs will be much greater than the challenge of rotating fields.”

– Watch for more of Ralph Pearce’s content on this topic at Country Guide.

The post Advanced corn hybrid with an RNAi trait to launch in Canada in 2023 appeared first on Farmtario.

Tracey Baute, entomologist for the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), published the Ontario results from the 2021 Adult Corn Rootworm Trap Monitoring Network on Feb. 25 on her “Baute Bug Blog.” 

The network monitored more than 600 traps across 15 U.S. states and five provinces in 2021. In Ontario, 84 traps were monitored in 22 counties with support from GFO and OMAFRA.

Why it matters: Survey results give crop consultants good information with which to advise farmers on pest control.

Baute said the Trap Monitoring Network grew out of a presentation delivered to GFO members last winter by Iowa State University entomologist Erin Hodgson. 

“It was obvious at that meeting that farmers in Ontario were recognizing the problem (of Bt resistance), and that we could learn from the States because they’ve been going through this already.”

Iowa farmers had hosted traps in their fields for several years but Hodgson and colleague Ashley Dean were working last year to make the program more user-friendly and create a digital platform for recording results. 

Following Hodgson’s presentation, GFO committed funding to cover Ontario farmers’ costs to participate in a similar program.

“We started to build (the program in collaboration with Iowa State) and then all of a sudden, all these other states and provinces wanted to join,” said Baute.

Four sticky traps were placed in each field, typically starting at the beginning of July and replaced each week for six to eight weeks. Adult beetles caught by the traps were counted.

An average of two beetles captured per day is generally agreed to be the threshold for developing Bt resistance if Bt hybrids are in the field. When the Ontario results showed fields in three counties —Huron and Perth in the southwest and Stormont Dundas Glengarry in the east — with 13 to 28 insects captured per week, the implication was clear. If Bt genetics are the sole measure used to combat the pest in these regions, Baute wrote in her Bug Blog, “crop rotation out of corn for a year should be considered.”

Less than one insect per week was captured in traps in Peel, Grey, Oxford, Simcoe, Chatham-Kent, Lambton, Elgin, Norfolk, Hamilton, Essex and Ottawa, leaving these areas at low risk of having Bt resistance develop. 

But Baute says she expects growers in those areas – along with their counterparts in counties identified as higher and medium risk — won’t take this as a signal to let down their guard. That’s because she believes the 2021 results will surprise many and be a call to action for crop advisors and sector leaders.

“Certainly, there were more counties where there are problems than were previously recognized,” she said. Results from western Quebec in particular were much higher than expected so farmers in eastern Ontario should take note.

The results from Huron and Perth should concern growers in neighbouring counties, many of which have high corn acreage.

“I’ve been saying that resistance is widespread across the province for the past two years but this just gives a visual representation to that,” Baute said.

Another takeaway is the distribution of the Northern Corn Rootworm variety. Typically green, it was thought to be mainly limited to eastern Ontario and less damaging than the Western CRW, which is typically yellow and black. 

Trap results from last year, however, showed that the Western variety is still dominant throughout Ontario and the Northern variety is present in most counties. 

“There is a slight difference between the species in how they overwinter and the Western does seem more able to develop resistance,” Baute said. “But they both can develop resistance to Bt, and they both can do damage to crops.”

Baute’s analysis of Ontario results from 2021 can be viewed at https://fieldcropnews.com/2022
/02/2021-ontario-crw-trap-network-results/.

The first-year project was a success in answering questions about rootworm activity, location, variety and how the problem compares to other regions.

From a broader perspective, the goal is to encourage crop rotation and Baute said the results give agronomists and crop advisors the information needed to encourage crop rotation.

Field management is part of the information that accompanies each set of trap results, so the results reinforce the understanding that Bt resistance “is really a problem with our continuous corn rotation.”

In Ontario, first-year cornfields had “very low CRW activity,” Baute wrote in the Bug Blog. Sites with three or more years of continuous corn had the highest degree of activity.

In some U.S. states where a two-crop corn/soybean rotation dominates, there were some soybean sites with traps that caught a significant number of CRW beetles. But in Ontario, the few soybean sites monitored had no CRW activity.

That’s not surprising, Baute said, given that aside from a continuous corn rotation still in use on some farms, a three-year rotation including wheat is dominant.

This year she wants to broaden the range of counties with, particularly in the east so they can track the possible migration of Bt resistance from Quebec. 

“I feel it’s more beneficial, too, to get them in higher-risk fields.” 

If growers have been using Bt hybrids as their sole strategy in corn or utilizing corn-on-corn rotations, she would like to see traps placed in those fields.

GFO has committed to funding farmer participation in 2022. It’s the same protocol as last year, although Baute plans to switch up the brand of trap used in Ontario. 

Contact her at tracey.baute@ontario.ca if interested in hosting traps.

The post Corn Rootworm trapping study will encourage crop rotation appeared first on Farmtario.

In 2020 there were several reports of corn rootworm injury to hybrids with below-ground protection from Bt traits. This suggests that Bt-resistant corn rootworm populations exist in Ontario. Continuous corn is at highest risk of a problem. Growers are encouraged to rotate out of corn for 2022. More information about this serious silage corn pest and how to join the corn rootworm trap network are available on Field Crop News.

Southwest

• According to AAFC, the region had above-average rainfall for September.
• Regrowth on hay fields is heavier than normal due to warm, wet conditions. While straight alfalfa won’t smother, grasses and clovers might. In mixed alfalfa/grass stands, wait until after a killing frost (-4 C for at least 4 hours) to harvest surplus growth. Leave 15 cm (6 in.) of stubble to trap snow for insulation. More details on fall harvest and winterkill risks are available here and here.
• Silage corn harvest is well underway, and yield reports so far are above average.

Central and East

• According to AAFC, most of the region had above-average rainfall for September, except for the southern part of counties bordering the St. Lawrence River.
• Regrowth on hay fields is heavier than normal due to warm, wet conditions. While straight alfalfa won’t smother, grasses and clovers might. In mixed alfalfa/grass stands, wait until after a killing frost (-4C for at least 4 hours) to harvest surplus growth. Leave 15 cm (6 in.) of stubble to trap snow for insulation. More details on fall harvest are available here and here.
• There was a light frost in parts of the region the week of September 27th. The riskiest time for prussic acid poisoning from sorghum species is between the first frost and the first killing frost. Producers should wait to graze or harvest sorghum crops affected by frost until after a killing frost to minimize risk.

Northeast

• According to AAFC, Algoma and Manitoulin had below-average rainfall for September. Sudbury had average rainfall for the month. The rest of the region received above-average amounts of precipitation.

Northwest

• According to AAFC, Rainy River and Thunder Bay districts had average rainfall for September. Kenora District received below-average precipitation for the month.
• Fall has been open and warmer than usual. The Ontario Crops Research Centre – Emo has not yet received a hard frost, though they stop counting CHUs on September 15.

To read the full September 2021 Forage report on the Field Crop News website, click here.

The post September forage report for Ontario appeared first on Farmtario.

They said efforts in the United States to slow the growth of resistance in corn rootworm to Bt-based control traits have not been effective.

Why it matters: According to entomologist Tracey Baute, there is no new corn rootworm control measure nearing development and approval, so it’s important Ontario agriculture strives to maintain as much effectiveness as possible in the existing Bt traits.

“The biggest thing, and the most important thing… is to rotate out of corn,” field crop entomologist Tracey Baute told a recent OMAFRA seminar on rootworm resistance. It was subsequently acknowledged that isn’t always practical, so other strategies were offered if immediate rotation isn’t in the cards.

Forage and grazing specialist Christine O’Reilly said in the top U.S. corn-growing states, where resistance has progressed faster than north of the border, one lesson learned was that early strategies, such as refugia and careful variation of stacked or pyramid hybrids, did not involve livestock producers who grow corn. As a result, corn-on-corn rotations persisted even though all top advisers urged their end.

“While we know that livestock producers aren’t the only people growing continuous corn, we do know they have a stronger incentive to do that because they need a high-yielding, high-quality source of feed,” she said.

O’Reilly said the challenge is not necessarily crop protection in nature, but rather a feed inventory problem.

Very little matches corn for yield potential. Even though livestock producers can suffer the most significant yield losses from infestations, owing to their use of the entire plant, they need good alternatives to replace that energy source.

Fodder beets are very high yielding, O’Reilly noted, with high energy. But “the equipment might be a challenge, so (beets) might be something more long-term.”

Until then, it’s grasses. Spring cereals, though, can serve as corn rootworm hosts; winter grasses, thanks to their high-growth stage coming when the rootworms aren’t active, are the most likely. As well, spring-planted sorghum species, which use a toxin to repel corn rootworm, have potential.

(Click here to learn more about O’Reilly’s examination of the various options.)

Both O’Reilly and Baute acknowledged that rotation away from corn might not always be practical. If you can’t, though, Baute urged growers to recognize that three of the four Bt proteins serving as below-ground corn rootworm controls in today’s pyramid hybrids are closely related. So if there’s resistance to one, there’s almost certainly resistance to all three.

“We strongly discourage just switching to a different pyramid hybrid in the hopes that’s going to solve the problem because we’re past that point now.”

If you can’t rotate, she advised, use an above-ground control. This may come in the form of a high-rate neonic treatment, or in the form of an investment in insecticide boxes on your planter. Either one requires planning.

A new intake just opened for Canadian Agricultural Partnership cost-share funding, and insecticide boxes, as well as custom pesticide applications are part of this program.

Another emerging option is bio-control nematodes. Work underway in New York state suggests these can be applied one time and last up to 10 years. Baute showed a side-by-side photo from one of the New York trial plots, and asked anyone interested in trying it to contact her.

Don’t, however, look to a high-rate insecticide during the growing season. Baute offered two reasons: they mask injury so you don’t know you’ve got a problem, and they could delay adult emergence and thereby increase the number of resistant survivors at the end of the season.

From a livestock perspective, O’Reilly said the most important strategy isn’t in the field but rather in the farm office — be it a mobile office or behind a desk. She urged producers to set up a conference call with both their agronomist and nutritionist. “Please, use the time this winter to get everybody on the same call… and come up with that crop plan that meets the feed needs.”

The post Lessons learned from U.S. struggle against corn rootworm resistance appeared first on Farmtario.

And, during a recent session hosted by OMAFRA, crop and livestock specialists encouraged Ontario’s livestock producers to consider rotating away from corn – or at the very least away from continuous corn – as part of a province-wide strategy to combat resistance by corn rootworm to the commonly used Bt-based control traits.

Forage and Grazing Specialist Christine O’Reilly outlined a number of possible sources for the energy that’s so readily-available to cattle and other livestock through corn and corn silage.

Ryegrasses, she says, can be “rocket fuel for ruminants,” with high digestibility. But because this manifests itself as high intake, and because yield is lower than corn, you’ll need more acres for silage.

It’s might be possible to give up some alfalfa acres if planting ryegrass, since protein content is elevated in high-quality ryegrass. There’s always a tradeoff, though; this means the crop is also hungry for nitrogen application.

Because it’s a spring-planted grass, ryegrass can serve as a corn rootworm host. But O’Reilly said European studies show the pest doesn’t persist past four years of perennial ryegrass.

The crop can be tough to terminate. You’ll need a high rate of glyphosate tank-mixed with Ultim. And make sure your timing and application are perfect.

The ability to host corn rootworm is more problematic for annual spring-planted cereals, so O’Reilly says fall-planted varieties are a better option when looking to expand the herd’s silage options. Fall rye, she noted, has an allelopathic effect on some subsequent crops, so she suggested fall triticale.

There could even be double-cropping potential if you chop the triticale for feed early enough to seed a sorghum species – either sorghum/sudangrass or sudangrass. Both – unlike forage sorghum – have multi-cut potential.

Because neither has much starch, more starch has to be found for the ration. With sorghum, planting in high populations can affect crops afterwards, so use lower seeding rates.

Betting on barley?

OMAFRA Dairy Specialist Tom Wright began his presentation by noting the good production maintained by Saskatchewan producers using barley-based rations. “Good management of different diets can certainly achieve similar results,” he said.

From both animal health and profitability perspectives, the biggest risk when moving away from a reliance on corn is in the milking herd. Heifers and dry cows can generally easier manage dietary changes. Wright advised dairy producers looking at decreasing corn to know the signs of sub-acute rumen acidosis. And don’t overlook how feed bunk behaviours influence how these changes in feeding regimes are manifested in the herd.

The post Silage options to rotate away from corn appeared first on Farmtario.