Scout oats for crown rust

Submitted by Sara Berges, Allamakee SWCD

Oats have been planted and the focus has shifted to corn and soybeans, but it is important to remember to scout oats for diseases. Oats should be scouted for early season crown rust starting at the 3-4 leaf stage. Crown rust is one of the most common and destructive diseases of oat plants. Buckthorn serves as an alternate host for crown rust and therefore may be especially prevalent around woodlands as buckthorn is quickly becoming a common invasive species. Initially crown rust appears as yellow to dark orange pustules on the leaf surfaces. As the infection spreads, the pustules will begin to turn black. Severe rust will reduce photosynthetic activity and yields. However, before you rush to apply fungicide, check variety trials to see if the variety shows any advantage from fungicide treatments.  Some varieties (such as Shelby 427) have shown little difference in yield between fungicide and no-fungicide trials.

If you decide to utilize a fungicide, remember that it only works when the disease is present and active.  They do not prevent the disease.  Make sure you scout often and spray at the first sign of infection, up to the flag leaf stage.  If you wait until the oat is headed and then notice the rust, the damage is already done and the fungicide won’t provide an economic.  There is a short 3-4 day window from disease appearance until the seed head emerges in which to effectively treat with fungicide.  Some of the fungicides that Grain Millers suggests include Stratego, Tilt, and Headline. Keep in mind, however, that fungicide application can delay maturity up to 7 days.

Organic oats have a much better market for food-grade production than standard oats. The main defense against fungal disease in organic oats is good genetic resistance and ensuring that buckthorn is not located nearby. Variety trails from Iowa and surrounding states provide information about disease susceptibility as well as yields, lodging potential, and test weight.

If you plan to harvest oats for feed or food, treat them like you would your corn or soybeans. Ensure proper fertility. Apply needed fertilizer at planting or soon after planting to reduce risk of lodging. Oats are often phosphorus and potassium lacking and pay attention to the N to P ratio. Too much nitrogen or not enough phosphorus will cause lodging.

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