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Navigating Tar Spot in Corn: The Value of Effective Management Strategies

Tar Spot, a devastating disease affecting corn crops, continues to challenge farmers across North America. With the recent surge in cases, understanding the disease’s impact and evaluating management strategies is crucial for maintaining yield and profitability. This blog explores the importance of timely intervention, the potential benefits of multiple fungicide applications, and the latest research on disease loss estimates.

The Rising Threat of Tar Spot

Tar Spot, caused by the fungus Phyllachora maydis, first gained significant attention in the United States around 2015. Since then, its prevalence has surged, particularly in the Midwest and parts of Canada. The disease manifests as black, raised spots on corn leaves, leading to reduced photosynthesis, premature leaf senescence, and ultimately, lower yields.

Recent studies have highlighted the economic impact of Tar Spot, with substantial yield losses reported across affected regions. For instance, the 2023 Corn Disease Loss Estimates from the United States and Ontario, Canada, underscore the severity of this issue. The report indicates that, in some areas, Tar Spot has caused up to 50% yield loss in untreated fields, emphasizing the need for proactive disease management .

Is a Second Fungicide Application Worth the Cost?

A debated topic in Tar Spot management is the effectiveness of multiple fungicide applications. A 2021 publication from the Crop Protection Network delves into this issue, exploring whether a second fungicide treatment is justified from a cost-benefit perspective.

The research suggests that while a single fungicide application can be effective in certain conditions, a second application may be necessary under high disease pressure or favorable environmental conditions for the fungus. The timing of these applications is critical. The first treatment is typically recommended at the VT to R1 growth stage, while a second application might be considered if wet and humid conditions persist, which favor the spread of the disease .

However, the decision to apply a second fungicide should be based on several factors, including disease pressure, weather forecasts, and the cost of the fungicide. The study notes that in some cases, the additional application can result in yield increases sufficient to cover the cost, particularly in high-value corn production systems.

Reflecting on the 2023 Corn Season

The 2023 corn season brought new insights into Tar Spot management. According to the seasonal summary from Field Crop News, the year was marked by variable weather conditions, which influenced disease development and spread. In some regions, early-season dryness followed by late-season rains created a perfect storm for Tar Spot outbreaks.

The summary emphasizes the importance of field scouting and early detection. Farmers who identified the disease early and implemented timely fungicide treatments were able to mitigate the impact more effectively than those who delayed intervention .

Best Practices for Managing Tar Spot

Given the ongoing challenges posed by Tar Spot, adopting a comprehensive management approach is crucial. Here are some key strategies:

  1. Field Scouting: Regular monitoring of fields for early signs of Tar Spot can help in making timely management decisions. Pay particular attention to fields with a history of the disease or those located in high-risk areas.
  2. Fungicide Application: While a single fungicide application can be effective, consider a second treatment if conditions are favorable for disease development. Consult with agronomists and review weather patterns to make informed decisions.
  3. Crop Rotation and Residue Management: Reducing the inoculum load through crop rotation and effective residue management can help lower the risk of Tar Spot in subsequent seasons.
  4. Hybrid Selection: Choosing corn hybrids with partial resistance to Tar Spot can provide an additional layer of protection. However, even resistant hybrids may require fungicide treatment under high disease pressure.

Tar Spot remains a challenge for corn producers, but with the right management strategies, its impact can be significantly reduced. As research continues to evolve, staying informed about the latest findings and adapting management practices accordingly will be key to maintaining healthy, productive corn crops.

Innovative tools like Spornado can play a crucial role in this effort. By providing early detection of airborne spores, Spornado helps farmers make informed decisions about fungicide applications, potentially reducing costs and improving crop health. To learn more about how Spornado can support your Tar Spot management efforts, visit our website at www.spornadosampler.com.

By staying vigilant and employing a combination of scouting, fungicide use, and cultural practices, farmers can navigate the complexities of Tar Spot and protect their yields for seasons to come.


References:

  1. Crop Protection Network. “Will a Second Fungicide Be Worth the Cost for Tar Spot Management?” Link
  2. Crop Protection Network. “Corn Disease Loss Estimates from the United States and Ontario, Canada – 2023.” Link
  3. Field Crop News. “2023 Corn Seasonal Summary.” Link
  4. Field Crop News. “Tar Spot Management in Field Corn.” Link

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