Fungicide seed treatment for winter wheat

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Farm Forum

I have heard of producers already planting winter wheat, so this isn’t the timeliest, but this activity will go on for some time. We at SDSU have been known to say, fungicide seed treatment is cheap insurance. While that’s true, but there are situations where they may not be justified, and in the promotion of IPM (Integrated Pest Management), we advocate using pesticides only when there is likelihood of an economic return. Commonplace use of any pesticide could potentially result in resistance, reduction in beneficial organisms, and it means that much more pesticide released into the environment.

In general, fungicidal seed treatments are used on wheat for three primary reasons: 1. To control soil-borne fungal disease organisms. This includes those causing seed rots, damping-off, or seedling blights, as well as the agents of the root rot complex, smuts, and bunts. 2. To control diseases caused by seed surface-borne fungal pathogens such as bunt. 3. To manage diseases caused by seed-borne fungi, such as loose smut.

If you are planting high quality, disease free seed into an environment that is unlikely to harbor soil borne disease organisms, and in conditions that will enable quick germination and emergence, fungicide seed treatment is probably not needed. The key is to manage risk, and use seed treatments when risk factors increase the chance of an economic return.

Soil borne fungal disease is more likely to pose risk when the field has a history of diseases like root rot complex, smuts, and bunts, and when planting into crop residue that hosts these diseases. Wheat planted into wheat residue, any grass crop, or a field that had grassy weeds growing in it poses a higher risk than following clean fallow or a broadleaf crop.

When planting seed with any degree of seed borne fungal disease such as loose smut or bunt, seed treatment has an excellent chance of providing an economic return. There are a few diseases such as scab (Fusarium head blight) and black point, which will not be directly expressed in the crop the seed produces. If planting seed containing either of these diseases however, fungicide seed treatment has been shown to improve germination and seedling vigor, which can also provide an economic return. Although it is not recommended to plant wheat seed that contains ergot, it has been found that seed treatment containing a triazole fungicide will reduce the viability of the ergot bodies and limit their ability to produce ergot spores.

Fungicide seed treatment will not compensate for poor quality seed, such as shriveled, mechanically damaged or impure seed, nor will it be effective against bacterial diseases.

Using fungicide seed treatments on wheat is an extra expense and takes time during a busy season. Treating seed is a preventative measure, it’s up to each producer to weigh the risks to determine if their use is justified.

For more information, access Emmanuel Byamukama’s article, “Planning Fungicide Seed Treatment for Winter Wheat” (http://bit.ly/1uoWwpk) or the “SD Wheat Crop Protection Guide: Seed Treatment” (http://bit.ly/1o7Baro).