By Scout Nelson
The belief in spraying fungicides early and often is being challenged in modern small grain farming. While this approach worked for older treatments in grapes, it is not effective with today's systemic fungicides for small grain diseases.
Experts now say fungicides should only be applied when disease is visible or if early-season conditions are extremely favorable for disease development. Applying fungicides without confirmed disease can cause crop stress, especially if the chosen fungicide interacts with herbicides. Always read product labels carefully before mixing.
A recent review of 16 years of fungicide research in North Dakota classified disease risk into four levels: very low, low, moderate, and high. In very low and low-risk cases—such as resistant varieties, rotated crops, and dry weather—fungicides added little to no yield improvement. Yield gains averaged 0.0% to 1.7%. Moderate and high-risk scenarios—such as wheat-on-wheat planting, high moisture, and susceptible varieties—showed yield increases of 4.6% and 4.3%, respectively. In fact, visible disease at the herbicide stage was only found in the high-risk category.
The decline in diseases like tan spot over the last decade is due to better resistance in varieties, increased crop diversity, and extended rotations. Longer breaks from wheat, particularly in no-till fields, can reduce tan spot by up to 70%.
In summary, adding fungicides to a herbicide program makes sense only when there’s a clear risk: planting wheat after wheat, growing a susceptible variety, and observing early disease.
Photo Credit:istock-fotokostic
Categories: Minnesota, Crops