Gray Leaf Spot: The Deadly Sin of Corn

Published on: 16:13PM Feb 16, 2010
Eric Tedford

If we could get a year without seeing gray leaf spot in a field, it would make for a glorious year for corn yields. However, the wicked reality of this situation is that we can’t! As each year passes, gray leaf spot threatens corn acres across the country and creeps up on growers. With all the other corn diseases out there, you may ask “What’s the big fuss with gray leaf spot?” Well gray leaf spot can be one of the most damaging and yield-robbing diseases in corn. According to the article “Effects of Foliar Fungicides on Corn Stalk Quality” by Carl Bradley of the University of Illinois, gray leaf spot can reduce grain fill by up to 50 percent. Reduced grain fill can result in stalk rot and ultimately cause standability issues in corn. Down corn on the ground negatively impacts yield potential and could cause issues with volunteer corn in following seasons, but that’s a topic for a later blog. So, how bad was gray leaf spot in 2009?
Many areas of the country witnessed gray leaf spot pressure at a severe rate. Southwestern Iowa was one of those areas that battled the disease at this level. Growers in that region of the state saw up to 20 of the brownish-gray stretched lesions on the ear leaf. As the disease eats away at leaf tissues, this inhibits the production of energy of the plant to ensure corn reaches its maximum yield potential. Each year climatic conditions have the potential to cause gray leaf spot to erupt and wreak havoc on fields. When conditions are wetter than normal, disease thresholds are usually higher. But hey, why try to predict the weather? Fungicide applications can help eliminate the stress of dealing with weather conditions potentially impacting yield by driving disease thresholds through the roof. Particularly a systemic fungicide with preventive and curative activity can defend against diseases that have struck and protect against those that may strike. In 2010, remember that gray leaf spot will be back - the question is “will you be prepared?”