Corn Vomitoxin Management Critical Considerations at Tassel

Mycotoxins, specifically deoxynivalenol (DON), commonly referred to as vomitoxin, has become a significant problem for Ohio corn growers. What was once considered an every-ten-year problem, has now become a yearly challenge in some sections of the state. DON contamination of grain is associated with Gibberella ear rot (GER), a disease caused by the fungus Fusarium graminearum. The Ohio State University Cereal Pathology Lab led by Dr. Pierce Paul has been researching and developing weather-based models to predict when weather conditions are favorable for DON contamination of corn grain. The current models predict when conditions are favorable for grain to be contaminated with at least 1 ppm DON.

The fungus that produces DON primarily infects corn ears during pollination while silks are wet (R1 growth stage). While insect feeding later in the growing season can be a route of secondary infection, this is a lower risk than during silking.

Effective management of DON requires the combination of multiple strategies. A model prediction can help you determine if a fungicide for DON management would be beneficial. Of the many fungicides available for corn disease management, two are considered to be the most consistently effective at suppressing GER and DON. These two products are Proline 480 SC and Miravis Neo. They have shown the best results when applied when silks are still wet (early- to mid-R1). The fungicide must penetrate the canopy and reach the corn silks when they are still wet to be effective. Applications made after silks are dry and brown are considerably less effective at reducing DON, with research showing that by 11 days past full silk, DON levels were the same as when no fungicide was applied. With the variation this year in plant growth stages and some fields having replanted corn in patches, perfect timing may be hard to achieve. Your goal should be to apply fungicide when the majority of the field is silking but before the earliest silks turn brown. While not as effective as applying the fungicide during wet silk, the DON reduction is greater with a V18 application than a brown silk application.

When applying fungicides, using water-sensitive paper attached to the silks can help you determine if your application is reaching the silks. Our work on using fungicides for DON management has primarily been conducted using high-clearance sprayers, either with drops or a boom over the top of the plant. Our coverage on water-sensitive paper increased when we used 20 gallons per acre compared to 15 gallons per acre. Last year, we conducted our first research trial to evaluate the use of a drone for fungicide applications in DON management. However, weather conditions did not favor disease development, and all of our plots had low DON levels. There was no significant difference between application methods or fungicide treatments. The drone application had less coverage on the water-sensitive paper on the ear leaf than the ground application.

Hybrid resistance is crucial, even with fungicide application, in achieving low DON levels at harvest. A hybrid with partial resistance will have lower DON at harvest than a susceptible hybrid when both have received a fungicide application for DON management. Extended harvest periods allow more time for DON production, particularly if harvest is delayed by wet conditions. An additional tool is to scout fields that pollinate during high-risk times for GER and plan to harvest those fields early.  

Throughout corn pollination this year, we will be updating the models and sharing estimates of the chance of grain in various parts of the state being contaminated with at least 1 ppm DON. This information will be made available through the C.O.R.N newsletter. Predictions generated by these models should only be applied to corn pollinating during the model’s prediction window, which is specific for each area of the state and field within that area. As a result, each week, predictions will likely change for the corn that is pollinating based on changes in weather conditions. Similarly, during any given week, predictions will likely change from one field to another based on hybrid maturity, hybrid resistance, planting date, and weather condition, all of which affect the silking/pollination window. 

It is important to remember that weather conditions are only one part of the disease triangle, and that all three sides of the triangle are needed for disease development, and in this case, for DON contamination to occur. The other two sides of the disease triangle are a susceptible corn hybrid and fungal spores being present at the time and growth stage when weather conditions favor infection, disease development, and toxin production. Consequently, the actual level of DON contamination will vary from field to field, depending on the susceptibility of the hybrid planted, tillage, and crop rotation, as well as weather conditions. Under favorable weather conditions, a highly susceptible hybrid planted no-till into corn stubble will likely be contaminated with DON well above 1 ppm compared to a tilled field of a moderately resistant hybrid planted after beans.   

DON model predictions are based on data from publicly available weather stations located at OSU-CFAES research farms and airports around the state. The two weather factors used to make predictions are temperature and relative humidity as number of hours within certain ranges or above certain thresholds. These factors can vary significantly over a few miles or with changes in elevation

The risk of DON contamination of grain, predicted using weather data from the ten CFAES weather stations, is low across the state for cornfields reaching the R1 growth stage. In other words, based on the prediction models, there is a very low chance of DON contamination of grain in fields in the vicinity of the weather stations that are now pollination being greater than 1 ppm. The current models were not developed to predict whether DON will be 2, 5, 8, or 10 ppm; they only predict whether DON will be ≥ 1 ppm, but not how much greater. Last year, the highly susceptible hybrids in the hybrid screening trial were over 1 ppm at all locations, as predicted by the model, while the hybrids with partial resistance under the unfavorable disease development conditions post-silk had DON levels of 0.1 ppm.       

Use predictions as one piece of information to help guide your DON management decisions. You should also consider the susceptibility of your hybrid and production practices when making management decisions. The results of the 2023 and 2024 DON hybrid resistance screening trial can be found at http://go.osu.edu/vomitoxin . This site also contains results from other Corn DON research projects done at OSU. Again, when weather conditions are favorable as suggested/predicted by the models, fields of highly susceptible hybrid planted no-till after corn will likely yield grain with DON above 1 ppm compared to a tilled field of a moderately resistant hybrid planted after beans.