Managing Key Pest Threats In 2026

Tuesday, April 21, 2026

Ken Currah on staying ahead of insects, weeds & diseases

By Mary Loggan

Ontario growers know that pest threats can quickly reduce crop yields and quality if not spotted and managed early.

Better Farming recently connected with Ken Currah, Certified Crop Advisor (CCA) and senior territory representative (London–Niagara) with BASF, to identify the top insects, weeds, and diseases likely to appear in Ontario fields this year, and the most practical ways to keep them in check.

Insect Pests

Currah reminds growers not to rely solely on winter conditions when planning for the upcoming season.

“Insects can be challenging to predict. Factors such as winter severity and weather patterns have not consistently proven to be reliable predictors for many key pest species.”

Recent dry falls have him watching soil dwelling insects closely.

“Dry springs and especially September and October weather typically lead to a higher likelihood of white grub and European chafer pressure activity.

“The dry weather lends itself to egg and pupae survival in the soil,” he explains.

“Following a dry season, we can lose lawn space and incur more lawn damage as the roots have been fed on in the fall, leading to overwintering loss.

“A similar dynamic can occur in winter wheat — if patchy winterkill is observed, these pests may be among the potential culprits.”

Corn rootworm (CRW) is a clearer and growing threat.

“CRW is more predictable,” Currah says. “Information shared by Jocelyn Smith (assistant professor in field crop entomology at the University of Guelph) at the Southwest Ag Conference earlier this year demonstrated the severity of this problem now that Bt-resistant populations are a reality that many producers are struggling with.

“Dry weather increased the severity of damage in 2025, and many weather models suggest continued dry trends through the 2026 growing season.”

He urges growers not to wait until they see severe lodging to make changes.

“CRW management revolves around rotating crops away from continuous corn, which for many requires some out of the box thinking to overcome challenges in feedstock supply and available land base.

“For resistant rootworm, I encourage producers to be proactive. Have a plan ahead of time and be willing to explore your options.”

Insect management advice

• Rotate away from continuous corn in fields with resistant corn rootworm, even if it forces changes to feedstock supply and land base.
• Scout winter wheat early for white grubs and European chafer; where damage is present, decide whether to terminate and re establish or manage thin areas and their impact on weeds and harvest.
• Build a proactive plan for resistant rootworm rather than reacting after the fact, and be willing to evaluate all rotation and trait options on the table.

Weed Pests

“With respect to weeds, multiple herbicide resistant waterhemp remains a leading concern and would be at the top of my list,” Currah says.

“This species has continued to spread into additional fields each year, posing increasing management challenges.”

The cost of falling behind on waterhemp is severe.

“It’s critical to avoid that first trainwreck field where the weed gets away on you,” Currah warns.

“Once waterhemp gets to six to seven inches in height, it’s beyond control stages for herbicides in most cases and crops.

“Seedbank management is critical, and that starts with herbicide programs with two planned passes of herbicide, and multiple modes of effective action included in the plan.

“For growers who have been satisfied in the past with reliance on post emergence herbicides and controlling weeds once they emerge and are visible, it’s time to utilize the pre emergent residual herbicide molecules in your operation and plan on second pass clean ups in the crop.”

Currah says that he is also seeing more trouble spots with Canada fleabane.

“Glyphosate resistant Canada fleabane has made a bit of a comeback, as many producers shift between soybean HT trait platforms and production costs hinder investment in herbicide plans that incorporate multiple modes of action against this weed.”

Weed management advice

• In soybeans and edible beans, build programs around a strong pre emerge residual base and treat post emerge herbicides as rescue, not the primary tool.
• For waterhemp and Canada fleabane, design programs around two planned herbicide passes and multiple effective modes of action rather than relying on a single post emerge cleanup; work with a CCA to ensure the plan is gap free.
• On Enlist E3 and XtendFlex acres, understand both the spectrum and best use practices for Enlist herbicide (2,4 D choline) and Liberty 200SN, and dicamba products, including crop stage and application conditions.
• Apply Liberty 200SN early post emerge when weeds and crop are small, using 20 gallons per acre of water and targeting hot, humid, midday conditions, and always pair it with effective pre emerge residual herbicides.
• Build residual layers using Group 15 actives such as pyroxasulfone, partnered with molecules like metribuzin (Sencor) in soybeans, and support chemical programs with simple, low cost cover crops to suppress annual broadleaf weeds.

Diseases

Later in the season, disease pressure can cause as much damage as insects or weeds if left unchecked.

Currah points to corn and wheat as crops where early planning and timely fungicide passes matter most.

Tar spot has quickly become a fixture in Ontario corn. Currah groups it with other common leaf and ear diseases.

“Tar spot in corn, along with secondary corn diseases such as northern corn leaf blight (NCLB) and ear rots like Gibberella, are areas of concern for corn growers every year.

“Tar spot is the largest yield-robber for many Ontario geographies, and growers in the ‘newer’ tar spot areas will need to recognize that dry weather, like what we experienced in 2025, is not a desirable management strategy.

“Understanding risk levels associated with weather and environment, and hybrid and fungicide management tools are key.”

He also sees an advantage in how timing lines up.

“Fortunately, the best application timing for fungicides to manage tar spot is the same R1 or Green Silk stage required for Gibberella ear rot and DON management.

“NCLB continues to be a somewhat overlooked and underrated disease, and agronomists should be vigilant for and be prepared to trigger fungicide applications in high yield scenarios where protection is warranted.”

In winter wheat, Currah expects stripe rust to remain an issue.

“In winter wheat, we should be vigilant for stripe rust and be prepared to manage accordingly.

“Most, if not all, fungicides have the rust diseases on the label, yet product selection can get confusing since Group 11 strobilurin products cannot be applied once the wheat head starts to split the boot.

“The crop must be treated immediately upon disease discovery — this has been proven in past experiences.

“A few days’ delay to the 20 to 50 per cent heading window for Fusarium head blight fungicides is most often costly to the producer. A CCA can support growers with these fungicide product decisions.”

Disease management advice

• In corn, treat tar spot as a major yield risk and assume inoculum is present on residue; plan fungicide applications around R1/green silk so tar spot and Gibberella and DON can be managed with a single, well timed pass.
• In wheat, scout early for stripe rust and be prepared to spray immediately once it is found, using products and timings that fit both rust and Fusarium head blight restrictions.
• Work closely with a CCA on fungicide selection and timing to navigate label limits (such as Group 11 cut offs) and protect high yield potential fields.
• Factor economics into timing, but remember that failing to treat pests above threshold can be much more expensive. Crop budgets are tight this year, and because disease management often falls toward the later end of the crop inputs investment cycle, growers tend to be more sensitive to fungicide expenditures. However, the costs of failing to manage diseases when present or pests when above thresholds can be devastating. A tight crop budget has no room for a yield or marketability penalty.

Looking Ahead

Currah expects pest pressure and management tools to keep evolving together, from resistant corn rootworm and multiple herbicide resistant weeds to tar spot and other emerging diseases.

He believes success will depend on planning and flexibility as much as on products.

“See & Spray technology and other sensing tools, as well as better use of residual herbicides, more mechanical weed removal, and at the same time, having a solid plan for resistant rootworm and other problem pests.

“See & Spray technology has indications that this will be a valuable tool. This will encourage growers to use pre-emergent residual products and reduce post-emergent herbicide use, which has many benefits for producers and resistance management.

“I also think we are on the cusp of an innovation and adoption curve when it comes to mechanical removal of weeds. Crop sprayers will always be busy, but as an industry, we will not be able to spray our way out of problem weed management.

“My concern with these topics is managing the economics of scale — the cost barriers to entry for growers.”

Overall, Currah encourages staying on top of pest pressure this season and taking action early.

“Have a plan and be willing to look at all options on the table and truly understand the potential impacts to your operation.” BF