About Powdery Mildew on Oats
The severity of powdery mildew outbreaks is dependent on climate, as the disease is favored by mild, humid weather. It often shows up when temperatures are between 59 and 72 F. (15-22 C.), but may disappear when the weather is dry and temperatures exceed 77 F. (25 C.). Powdery mildew spores can overwinter on stubble and voluntary oats, as well as on volunteer barley and wheat. The spores spread by rain and can also travel great distances in wind.
Powdery Mildew Symptoms
Powdery mildew of oats appears as fluffy white patches on the lower leaves and sheaths. As the disease progresses, the cottony patches develop a gray or brown powder. Eventually, the area around the patches and the underside of leaves turn pale yellow, and leaves may die if the outbreak is severe. You may also notice tiny black spots on oats with powdery mildew. These are the fruiting bodies (spores).
How to Treat Powdery Mildew
There isn’t much you can do for oats with powdery mildew. The most important thing is to plant disease-resistant varieties. It also helps to keep volunteer grains under control, and to manage stubble properly. Fungicides may be of some help if applied early, before the disease becomes severe. However, the limited control may not be worth the expense. Even with fungicide, you aren’t likely to totally eradicate the disease. Also, keep in mind that powdery mildew is resistant to some fungicides. If you’re thinking about using fungicides, talk to the crop experts at your local cooperative extension office.
