The Critical Role of Disease Management in Corn Silage Quality
As the tasseling stage approaches, corn disease scouting and management become paramount in maintaining the quality of silage. Diseases can significantly reduce silage digestibility, milk production per ton, and cause rapid plant death, affecting silage moisture and fermentation.
Importance of Scouting for Corn Diseases
Leaf diseases can lower silage digestibility, leading to reduced milk production per ton. It is vital to scout for these diseases diligently. Ear rots, such as Gibberella ear rot which produces vomitoxins, are particularly challenging to identify. The OSU Cereal Grain Pathology lab is developing a Vomitoxin disease prediction model to help farmers make informed management decisions based on weather conditions favorable for disease development. Currently, weekly risk assessment updates are provided through the corn newsletter (corn.osu.edu).
Fungicide Application and Timing
When using fungicides for disease management in corn silage, it is crucial to consider the preharvest interval, which varies from 7 to 36 days. Research sponsored by the Ohio Dairy Research Fund in 2022 and 2023 examined Deoxynivalenol (DON) and Zearalenone management across various corn hybrids and application methods. Only two fungicides are labeled for Gibberella ear rot management: Proline and Miravis Neo. These should be applied at the VT/R1 stage when silks are green and wet to reduce DON levels effectively.
Optimal Conditions for Fungicide Efficacy
Disease development is influenced by humidity levels above 80% and temperatures between 59°F and 86°F, with consecutive hours in this range being critical. Proline, containing only Prothioconazole, is effective against ear rot but less so against foliar diseases like Gray leaf spot and Tar spot. Miravis Neo, with three active ingredients, offers broader disease control, including excellent efficacy against Gray leaf spot and good control of Tar spot.
Fungicide Application Methods
Research has shown that hybrid susceptibility to DON varies, but all hybrids respond similarly to fungicide application. Effective application requires ensuring the fungicide reaches the silks. The ideal application time is when silks are green and wet. A study in 2023 compared different application methods: a boom sprayer, a boom sprayer with drops, and a drone. All methods significantly reduced DON levels from 1.9 ppm in untreated fields to 1.1-1.2 ppm in treated fields.
For boom applications, a 20-gallon-per-acre rate provides better coverage than a 15-gallon-per-acre rate. Drone applications used a 2.5-gallon-per-acre rate with large droplet size nozzles to ensure product penetration to the silks.
Achieving high-quality corn silage requires a multifaceted approach: selecting resistant hybrids, timely and effective fungicide applications, and favorable weather conditions. By integrating these strategies, farmers can enhance silage quality, ensuring better milk production and overall herd health.
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