As we have discussed with many of you over the past year Pioneer has been working diligently to test and rate our lineup of corn hybrids against Tar Spot. Before getting in depth on the rating scale, lets review on what tar spot is.

How to identify Tar Spot

This disease can be best described as small black lesions that develop in the lower part of the canopy and will move up the plant as they spread. These lesions will begin as sparse spots on the upper side of the leaf but will spread and continue to cover the leaf surface as the infection worsens.

How Does Weather Impact Tar Spot

Tar spot has been proven to overwinter on corn residue. After the disease pressure seen during the 2021 growing season it is easy to believe the inoculant for the disease exists in most of our fields. With that being said what weather conditions should we watch out for in 2022 that may lead to infection. Most of the recent data around Tar Spot shows that it favors cooler temperatures ( 60-70 F), high relative humidity, frequent cloudy days, and 7+ hours of dewey nights. As a reminder Tar Spot is a polycyclic disease which means it will continue to infect over multiple generations which is why we can see such large amounts of pressure develop so quickly.

How Do Our Hybrids Rate?

While we do see efficacy of several different fungicides against Tar Spot, genetic resistance is still seen as the best tool we have to fight this disease. As a general statement, our studies have shown increased host resistance in earlier maturing hybrids than fuller season products. While this may just be a current trend of the genetic families we are currently planting, below you will see how our corn hybrids rate individually.

As always, we will scout and answer questions that you have when we draw closer to fungicide application. We just wanted to get this on your radar as tar spot can be devastating. With commodity price and the opportunity for big returns in 2022, we feel it prevalent to plan ahead, book fungicide, and stay active with scouting during the growing season. Please feel free to reach out to our team if you have any specific questions on products or how this disease could impact your operation.