By Pierce Paul
I never recommend planting a small grain crop after another small grain crop, as planting wheat after barley for instance or barley after wheat increases the risk of diseases such as head scab and take-all. However, this year, some growers do not have much of a choice; soybean will not be harvested in time in some fields for them to plant wheat, so they will either have plant wheat after corn harvested for silage or after wheat. If you do end up planting wheat after corn or wheat, here are a few tips that could help to reduce the risk of having major disease problems next spring:
- Select and plant the most resistant variety that you can find. Check the Ohio Wheat Performance Trials report (https://www.oardc.ohio-state.edu/wheattrials/table6.asp?year=2019), and select a variety with resistance to as many diseases as possible. Give priority to head scab, Stagonospora, and powdery mildew resistance.
- If conditions become favorable for disease development in the spring, resistance alone will not control head scab. Plan to apply a fungicide if it becomes wet and humid during flowering. However, we still have time to think about fungicide application for head scab control, let us continue to explore fall management options.
- If you cannot rotate away from a small grain crop, the next best option to reduce spore build-up in the field is tillage. Most of the common leaf and head diseases in Ohio and even some root diseases survive in crop residue. Tillage will bury residue, leaving fewer spores available to infect the newly planted crop. Tillage will also speed-up residue decompositions.
- Plant after the Hessian fly-free date, as cool fall conditions are less favorable for spore production and infection. See the article Considerations for 2019 wheat planting by Andy Michel, Laura Lindsey and Pierce Paul for more on planting date.
Planting date and foliar fungicides will not control root diseases such as take-all, and wheat and barley varieties with resistance to talk-all are hard to find. So, here are a few additional tips that will help to reduce take-all problems next spring, if you happen to plant wheat after wheat or another small grain crop this fall:
- Nutrient management: Take-all is favored by nitrate forms of nitrogen and suppressed by ammoniacal and slow-release forms of nitrogen. Manganese deficiency has also been associated with increased levels of take-all. In general, any form of nutrient stress (lack of essential and trace elements) could increase take-all.
- Soil pH: Take-all it is also favored high pH, so applying lime will generally increase take-all, particularly if the pH is elevated above 6.
- Tillage will help to reduce take-all for all the reasons listed above.
- Crop rotation away from small grain crops for 1-2 seasons is often the best way of managing take-all, with soybean being one of the best rotational crop. However, if you plant wheat or barley into a(n) (abandoned) soybean field that had a lot of grassy weeds you could still have problems with take-all.