North Dakota State University has received a number of calls recently about the use of fungicides, post-tasseling on corn. Fungicide use in corn has been growing in importance in the USA. Fungicides can be an effective tool for controlling diseases, if genetic resistance is inadequate and when disease pressure is high.

In North Dakota it is difficult to find foliar diseases on corn. Therefore, fungicide use on corn has been more directed towards apparent plant health benefits whose physiological basis has been difficult to elucidate. When asked if fungicide should be used in corn, we usually respond by recommending a fungicide if it appears that foliar diseases will be problematic. Since diseases will not likely be limiting, the conversation then centers around the likelihood that a fungicide will provide a profitable yield response in the absence of disease.

From research conducted at Carrington and Prosper over the past few years we found that a fungicide (in these experiments Headline was used) a positive yield response of greater than 6 bu was obtained in 4 of 10 site years (see Figure 1). NDSU researchers used 6 bu as the point where the cost of the fungicide plus the cost of application might equal the value of the extra grain produced. In 4 of the 10 site years, however, the yield of the fungicide treated plots was less than or equal to that of the untreated plots. 

Researchers are continuing this work with fungicides, but the current data does not demonstrate a consistent or a compelling benefit for their use in our environmental conditions. In fact, current data suggest that there is about an equal chance of getting no response (or a negative response) as there is of making additional money with fungicides on corn and a 6 in 10 chance of not making a sufficient return to pay for the cost of the fungicide application.