Tar spot continues to be a growing concern for Ontario corn growers, and 2025 has been no exception. This year, the disease followed a pattern similar to previous seasons—first appearing at low levels in early July in Elgin County. Hotter, drier summer conditions kept tar spot development relatively low until August, when more favorable weather led to a late-season resurgence. With fungicide applications in place, yield losses are expected to be less severe than in recent years.

In fact, tar spot has quickly become Ontario’s most damaging corn disease. In 2024, it was the top yield-reducing disease in the province, responsible for an estimated 5.9 million bushels in losses (Crop Protection Network).

First Scouting Report vs. Spornado Early Warning

The first scouting report of tar spot in Ontario corn was on July 14, 2025, in Elgin County. This aligns closely with previous years.

But what’s remarkable is that Spornado detected tar spot spores in the air on June 19, 2025 – more than three weeks before visible disease symptoms appeared in the field. This early warning provided growers with valuable time to assess disease risk and make more informed spray decisions.

This gap between spore presence and visible symptoms demonstrates why in-field air sampling is so valuable. Tar spot often establishes before anyone sees it on leaves, meaning farmers relying on scouting alone risk detecting the disease too late to prevent losses.

Resources

For more details on tar spot development in Ontario, see the latest updates from Field Crop News and the Crop Protection Network. Both provide timely scouting reports, management strategies, and research updates to help growers stay informed.

---

Spornado Takeaway: Why Early Detection Matters

Spornado’s ability to detect tar spot spores weeks before symptoms appear gives growers the chance to make proactive, data-driven spray decisions. By staying ahead of disease, farmers can reduce unnecessary applications, protect yields, and improve return on investment.

California agriculture is entering a new phase in pest management. The California Department of Pesticide Regulation (DPR) is rolling out a Pesticide Prioritization Process as part of its Sustainable Pest Management (SPM) Roadmap , a move designed to reduce reliance on certain pesticide tools and accelerate adoption of lower-risk alternatives.

Read the original National Nut Grower article here: California rethinks sustainable pest management

Why This Matters

For permanent crops like almonds, pistachios, and walnuts, pest and disease control isn’t optional, it’s essential for protecting yields and profitability. But in many cases, growers depend on a small toolbox of chemistries, carefully timed to hit critical pest or pathogen windows.

Under the SPM process, some of these products could be prioritized for phase-out. That means there will be, tighter spray options, increased need for non-chemical or reduced-risk approaches, and greater pressure to prove economic feasibility of alternatives

What Growers & Agronomists Are Saying

Industry feedback, including some from the American Pistachio Growers, emphasizes that regulatory decisions must weigh economic viability alongside environmental impact, only phase out products if there are effective proven alternatives, and new strategies must be backed by research, education, and technical assistance.

Many nut growers are already using sustainable methods; mating disruption, beneficial insects, trap-based monitoring, and precision spraying, but there’s a gap: How do we know these alternatives are working in real time?

The Critical Role of Data

As the regulatory landscape changes, data becomes a grower’s best risk management tool. Specifically; Early detection of pests and diseases allows growers to avoid prophylactic sprays and only treat when necessary, Baseline monitoring across regions can guide cooperative action and help avoid surprises, Evidence-based results make it easier for regulators to approve, and for growers to trust, alternative control methods.

What We Can Do Now

Here are a few proactive steps for the 2025–2026 seasons:

1. Engaging early in DPR’s process, public input now can shape how “viable alternatives” are defined.
2. Invest in monitoring and forecasting tools to detect pest or disease pressure before it’s visible.
3. Document the impact yield, cost savings, spray reductions, or new approaches you try.
4. Collaborate regionally pests don’t respect fence lines, and coordinated monitoring reduces blind spots.

Where Spornado Fits In

At Spornado, we work with growers, researchers, and advisers to provide molecular-level early warning for airborne crop diseases. Our samplers and lab testing detects spores days to weeks before symptoms, support decision-making during spray program transitions, and help validate the effectiveness of new, lower-risk control methods.

As California moves toward sustainable pest management, we believe science-backed, grower-led data will be the bridge between policy goals and practical, profitable farming.