Jason Hartschuh, Assistant Professor, OSU Extension Field Specialist, Dairy Management and Precision Livestock, Ohio State University
Corn hybrid selection is critical to maximizing your cow's production. When selecting hybrids, we usually consider factors like digestibility, energy, crude protein, milk per ton, and milk per acre. Foliar corn disease susceptibility is a critical factor to consider as it can affect both grain and forage quality, requiring a multi-prong approach to managing feed quality. Stalk and ear rots can be even more detrimental as they produce mycotoxins. Deoxynivalenol (DON), also known as Vomitoxin, can cause significant feed quality challenges in both silage and grain. The same fungus that produces DON can produce Zearalenone (ZEA), an estrogen mimicking mycotoxin that can also create many challenges for dairy cows.
Foliar Disease
Foliar diseases can reduce yields but cause fewer grain quality issues unless they kill the corn plant prematurely, lowering test weight. However, foliar disease can cause feed quality issues in silage. Tar Spot is the most concerning as it is an aggressive disease that can kill corn plants rapidly, leading to silage moisture that is too low for proper fermentation. Even when a foliar disease does not kill the corn plant, it can lower the digestibility of the corn silage, decreasing the energy and milk per ton. When a corn plant is infected with a foliar disease, its natural response to fight off the disease, which includes hardening the cell walls around the infection so that the disease does not spread further along with the death of plant tissue in the infected area. As the cell walls around the disease area thickens, they become less digestible and so does the dead plant tissue in the diseased area, lowering the quality of your silage. Under severe disease pressure, we have seen highly digestible brown midrib (BMR) corn hybrids become less digestible than a non-BMR silage-type hybrid.
Management of corn diseases starts with hybrid selection; however, for emerging diseases such as Tar Spot, there may not be resistance ratings available in the seed catalogs. Selecting hybrids that have good disease resistance for Gray Leaf Spot and Northern Corn Leaf Blight is your first step so that those diseases are managed through plant genetics. Then discuss with your seed salesman what they are experiencing for Tar Spot resistance. Layering genetic resistance with fungicide applications when disease is present can maintain forage quality. When using a fungicide for foliar disease control, be sure to select one that controls the diseases you have presently. Information on fungicide efficacy for foliar disease can be found here: https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-corn-diseases.
Gibberella Ear and Stalk Rot
The fungus Fusarium Gaminearum can infect the corn stalk by causing stalk rot, which includes rot in the stalk, cob, and grain. In both locations (ear and stalk), the mycotoxins can be produced with major concerns coming from DON and ZEA. With your support from the Ohio Corn Marketing Board and Ohio Dairy Research Fund, OSU Extension and OSU Plant Pathology have been researching a systems-based approach to DON management. This systems-based approach includes hybrid resistance screening of both corn grain and corn silage, hybrid infection reaction characterization, fungicide application method screening, weather modeling to predict disease levels, and post-harvest cleaning of corn grain.
Our first hybrid screening project for DON was done in 2023 with only corn grain, but in 2024, we conducted a screening of both grain and silage hybrids. We will continue this program in 2025. The grain screening results can be used to help with hybrid selection for both grain and silage, but corn silage can have DON toxins from both the grain and the stalk. There is no correlation between high amounts of DON in the stalk and high quantities of DON in the grain and ear. The plant resistance traits for these two areas of disease infection are probably different so there is a chance that a corn hybrid with partial resistance to DON development in the ear may not have resistance to DON development from stalk rot.
In 2024, we lost half of our silage screening plots to due to flooding after planting at the research station. This led to us only having results from the Enogen plots, which were grown in a different area of the farm to maintain the stewardship guidelines. Weather conditions for disease development in 2024 were not favorable, so across all screening trials, DON levels were low. The results from the Enogen hybrids are in Figure 1 below. Hybrids with a different letter at the top of the bar had statistically different DON levels. These plots had higher DON levels than most corn silage in the State this year. The plots were inoculated with fungal spores to cause ear rot and DON during pollination. These hybrids ranged from 0.06 to 1.46 ppm DON. Of the 11 hybrids submitted, 3 of them averaged greater than 1 ppm and 7 averaged less than 0.5 ppm. Under high disease pressure such as inoculation, no hybrid is 100% resistant. When using results from these screening trials, consider that hybrids with higher DON levels are susceptible while low hybrids are partially resistant. Under favorable weather conditions for disease development, some of the low hybrids may have been higher. One strategy to evaluate the hybrids that you grow is to test every hybrid every year. If using silage bags, test each hybrid at feed out; for bunkers and silos, sample hybrids as they are put in. DON levels can change during the first 30 to 60 days fermentation. The goal for high-producing dairy cows is to keep the complete ration below 1 ppm DON.
abcdHybrids with different superscripts differ.
The corn grain hybrid screening project had 80 hybrids submitted in 2023 and 90 hybrids submitted in 2024. DON levels in 2023 were much higher than in 2024. Of the 80 hybrids submitted for evaluation, 24 of them had DON levels greater than 5 ppm in at least 1 of the 3 locations and 28 hybrids averaged less than 2 ppm across the 3 locations. The DON levels were much lower in 2024, with the 2 locations we have completed the data analysis only averaging 0.4 ppm DON across all 90 hybrids. The range however was from no DON detected to 3.7 ppm. Grain hybrid DON screening data can be found at: go.osu.edu/vomitoxin
Hybrid selection is an important first step to producing feed that has low levels of DON and other mycotoxins. The second step to consider is a fungicide application; however, only Proline and Miravis Neo currently have labels for the control of Gibberella Ear Rot. Using fungicide for Gibberella Ear Rot management requires perfect timing. The fungicide must be applied while the silks are wet and must reach the silks during application. Once the silks turn brown and dry, the fungicide doesn’t move into the ear where the fungus is hiding. A fungicide can only lower the DON levels but cannot lower a susceptible hybrid to 0 ppm DON when weather conditions favor disease development. Through an integrated pest management approach, DON can be controlled so that you have clean corn silage.