March 20, 2023


by Justice Keefauver

In southeast, MN we are very aware that this year had anything but dry conditions! From planting until now we have experienced some heavy rains and cooler temps. With the conditions we have endured this year, there is much concern surrounding disease. Two corn diseases that stick out this year are Common Corn Rust and Northern Corn Leaf Blight. Questions often asked include: “What impact can these have on my yields?” and “How can I manage these diseases?”

“What impact can these diseases have on my yields?”

Common rust is favored by cool, humid conditions, found on upper and lower leaf surfaces, and distinguished by elongated red to cinnamon-brown pustules. This year I have seen a lot of early signs of this disease and moving into harvest we could see potential issues regarding yield and stalk rot. Rust can alter the photosynthesis process that is needed to optimize ear potential. Also, this can cause less sugars to be produced, so plants use stalk carbohydrates to help fill kernels which causes weakened stalks and potential for stalk rot.

Another concern that recently I have been seeing more and more of is Northern Corn Leaf Blight (NCLB). Early NCLB symptoms appear as long, narrow, tan lesions that form parallel to leaf margins. As these lesions develop, the classic symptoms of NCLB will be observed: long, oblong, or “cigar shaped” tan or grayish lesions. The past two weeks fields have really shown developed lesions.  NCLB can reduce yield when conditions are favorable for early development of the disease. Lesions reduce the leaf area of the plant that carries out photosynthesis. Infection occurs during periods of moderate (64° to 81°F), wet, and humid weather. NCLB can have detrimental effects on yield and plant potential. Severe NCLB development during grain fill can result in yield losses of 30 percent of more.

“How can I manage these diseases?”

It is crucial to understand the severity of these diseases, how to scout for them, and how to make effective management decisions from choosing the right seed to in-season fungicide applications. Some management practices that are important to keep in mind to mitigate the risks associated with disease include:

Choosing Resistant Hybrids

  • Work with your agronomist to decide the right hybrid given the history of disease on those acres.
  • Know the hybrid’s disease susceptibility and response to fungicide score (RTF).
  • Reflect on this falls harvest, and start thinking about the appropriate seed plan!

Chemical Disease Control

  • Given favorable weather conditions be sure to scout for early symptoms of diseases before tassel
  • Apply a foliar fungicide at tassel on susceptible hybrids to optimize protection for your crops
  • Always a good idea to apply a fungicide when planting corn on corn.

Crop Rotation

  • With a reduced tilling system, rotating crops can serve as a sound cultural way to control disease.


Fungicide Opportunity

Historically in the past couple years growers are seeing great response to fungicide applications on their corn anywhere from 10 to 30 bushels. This increase in bushels per acre are raising eyebrows! There are many cases this year where individuals are incorporating a fungicide application on their corn for the first time. I’m excited to see the response to fungicide applications given the favorable conditions for disease we have faced this year! It’s great to see that more and more are trying to protect their crops, and optimize ROI within their operations. I know many acres where Trivapro fungicide was applied are already showing positive signs.

Trivapro Fungicide

Syngenta’s fungicide Trivapro has shown a step change in control of diseases including rusts, leaf spot, Northern Corn Leaf Blight and more. Trivapro contains three complementary and non-cross-resistant modes of action (strobilurin, triazole, SDHI). Fits easily into corn, soybean and wheat programs. Mixes well with other products. Unique chemistry designed for maximized protection against rust. Demonstrated preventive and curative fungicidal activity. Excellent residual control.

I hope everyone has a safe and successful harvest!