Late Season Wheat and Barley Disease Management
Our wet and rainy conditions during the pollination period of barley and wheat has continued into the grain fill period, increasing the risk of head scab in those crops. For those of you able to attend last week’s small grain field day at the OARDC Schaffter farm Pierce Paul, OSU Extension small grain and corn pathology specialist, provided some excellent examples of and teaching about, late season disease management, including head scab on barley and wheat. Today, I am featuring an article by Pierce Paul providing some management practices for late season diseases of wheat and barley.
“Cool weather and moisture after flowering often means extended grain-fill and high yields, especially when disease levels are as low as they were at the time of pollination and early grain development in some fields. However, excessive rainfall associated with the cool temperatures could increase the severity of diseases that thrive under cool conditions. Our barley and wheat crops are now well into grain-fill and even turning in many locations. At this development stage there is very little you can do about late-season diseases. The pre-harvest interval for some of the best fungicides is 30-45 days, which mean that they are now off-label in most areas, given that harvest will likely begin in less than 30 days.
If you did apply a fungicide at heading or flowering, that should have helped to delay disease spread within the field and up the plant, minimizing grain yield and quality losses. There are still lots of fields out there with healthy flag leaves, and by the time those leaves eventually become diseased, the yield would have already been made. An application of Prosaro or Caramba at heading (for barley) or flowering (for wheat) would have also helped to reduce head scab and vomitoxin. It is important that growers realize that these fungicides only suppress the disease. That said, you may still see some scabby heads in your field. Therefore, now is the time to walk those fields to see if head scab is present and how much – this will help you to plan your grain harvest and handling strategies.
Consider harvesting fields with moderate levels of head scab (5-10% incidence; that is, 5 to 10 heads out of every 100 with some scab) at the very first dry-down (18-22% moisture). Harvesting early will reduce problems with sprouting and further contamination with vomitoxin, once the grain is dried (13-15% moisture) and stored. You should also increase your combine fan speed to blow out scabby, light-weight kernels. We have found that increasing the air flow through the harvester can reduce scabby grain by an average of 40% and vomitoxin by an average of 17%.”