A vomitoxin (Gibberella ear rot/DON) risk forecast model developed by The Ohio State University Cereal Pathology Lab, thanks to support from the Ohio Corn Marketing Program, is now available. The risk forecast model was developed using weather data and corn grain DON levels from 170 Ohio field environments. Use this model to estimate the risk of DON contamination in your field reaching or exceeding 1 ppm through the new web-based Crop Risk Tool hosted by the Crop Protection Network.
Vomitoxin risk forecasts are updated daily based on weather conditions during a 21-day window before silking, and a 7-day forecast to support informed management decision-making. We recommend using this tool for each field in your operation. During the summer, weather conditions often vary significantly from one field to the next. For instance, pop-up showers and high relative humidity within a field during and shortly after silking will increase the risk of vomitoxin contamination compared to a field not experiencing those same conditions. Check the model at silk emergence and 50% pollination to make the most informed decisions about your risk of vomitoxin.
Risk projections can be used to determine if a fungicide application is necessary to help reduce vomitoxin levels. Only two fungicides, Proline and Miravis Neo, are labelled for Gibberella ear rot and vomitoxin control, but they must be applied during wet silk to be effective. This is the same time frame that ears are affected by the fungus Fusarium graminearum, which causes Gibberella ear rot and produces vomitoxin.
The risk prediction model is only one tool to help you lower your vomitoxin contamination levels. Based on hybrid resistance, we have seen vomitoxin contamination under the same field weather conditions vary from less than 1 ppm to greater than 20 ppm. Conversely, vomitoxin contamination may vary among fields with the same levels of hybrid resistance based on differences in silking dates and associated weather conditions. This is where vomitoxin predictions must be made separately for each field and hybrid.
To learn more about hybrid resistance screening trials in 2023 and 2024 visit: http://go.osu.edu/vomitoxin. Additionally, consult with your seed supplier to determine past DON levels associated with selected hybrids. Since this model is designed to predict the risk of DON levels being greater than 1 ppm regardless of resistance, a fungicide application may be warranted on highly susceptible hybrids at a lower risk level than hybrids with known resistance.
Follow the steps below to use the Crop Risk Tool or view a step-by-step video at https://www.youtube.com/watch?v=xJ707vRQkjE.
Step 1: How to Access the Tool
To access, click on the green button “Access The Forecasting Tool” on the landing page https://cropprotectionnetwork.org/crop-disease-forecasting
Step 2: How to Set Up Location
Either zoom in and find the location you are interested in and drop a pin, or you can upload a prepopulated .csv file with GPS coordinates (latitude, longitude as decimal degrees in separate columns). Then click on the “Fetch Weather Data” button to retrieve GPS-specific weather conditions.
Step 3: Finding Probabilities of Risk
Select the appropriate crop (corn in this case) and the included disease forecast models will be displayed on the righthand pane of the tool. You will need to view each disease risk separately. Click on “Gibberella ear rot/DON” to see vomitoxin risk predictions and on “Tar spot” or “Gray leaf spot” to see separate risk predictions for tar spot and gray leaf spot.
Step 4: Interpreting the Data
The Crop Risk Tool should only be used during periods when crops are susceptible to the disease. For Gibberella ear rot/DON this is the period while silks are wet from VT through R1. During this time, the more days that are shown as high risk, the more likely corn ears may be infected with Fusarium graminearum spores which cause Gibberella ear rot and produce DON. Risk forecasts for gray leaf spot and tar spot are only applicable between growth stages V10 and R3. Also, keep in mind that the pathogen must be present in the field along with a susceptible hybrid for disease to occur.
The risk projection below demonstrates how risk can vary within a region. The first projection encompasses the four corners of Crawford County, along with the county seats of Seneca County, Tiffin, and Morrow County, Mount Gilead, with the greatest distance between these locations being 40 miles. While risk prediction across all six locations is low, the Lykens locations experienced a slight increase in risk due to weather on July 17 (silking date for that field), and another elevated risk is projected for July 22 (another silking date) in Lykens and Galion. Each dot on the prediction line represents a different day; hovering over a dot that corresponds to your silking date will give you a numerical risk prediction as a percentage. The higher the number, the greater the risk of DON being greater than 1 ppm. The more days of elevated risk, the greater the chance that your corn may have DON levels exceeding 1 ppm.
The second projection below is from the same time frame, but from the Mahoning County area. While the risk was still mostly low, three of these four areas showed a slightly elevated risk on July 17th, but the risk declined again quickly. In years when we have seen extremely high DON levels, the risk prediction model was red for multiple days.
The Crop Risk Tool is powered by the National Predictive Modeling Initiative of the USDA-ARS and was developed in collaboration with the University of Wisconsin-Madison Department of Entomology. Funding for individual crop disease forecasting tools was provided by the National Corn Growers Association, the North Central Soybean Research Program, and the United Soybean Board. The funding for the Gibberella ear rot/DON model was provided by the Ohio Corn Board. Due to variable weather conditions, pathogen loads, and hybrid susceptibility, there is still a risk of DON contamination when the model projects a low risk of DON levels greater than 1 ppm.