Early Season Scouting in Small Grains: Tan Spot
With the overcast and humid days which many parts of the state have been experiencing in the last week, be sure to scout smalls grains for signs of early tan spot infection. Tan spot will be particularly prevalent on previous wheat ground. Spring wheat in trials on the Northwest Research and Outreach Center at Crookston has 100% incidence with tan spot. There is some tan spot in the winter wheat. Early signs of tan spot in fields south of Moorhead, Minnesota, have also been identified.
Tan spot is identifiable by the brown spots often surrounded by a yellow halo that appear on leaves. These may run together to form patches or larger areas of yellowing and browning.
Be careful not to mistake nitrogen deficiency or symptoms of BYDV for tan spot.
If you do see tan spot, you can use a tank mix with herbicide and fungicide for control of this disease. If left unchecked, this disease will continue to progress and will impact yield. A number of different fungicides can be used for control of this disease ( see table) This year, we are interested in collecting isolates of tan spot. So if found, please can you contact me via e-mail firstname.lastname@example.org BEFORE you spray and we will try to collect a sample.
BYDV could be another disease that we see this year if aphids become prevalent (particularly bird cherry oat and English grain aphids). Symptoms of BYDV will vary depending on the crop, variety and the growth stage at which the plants become infected. General yellowing of the leaves are common. Reddening also occurs, especially in oats, but is dependent upon variety and crop. These symptoms will usually start from the tip of the leaf and work their way down either edge of the leaf. Eventually the whole leaf may become yellow. If plants are infected with the virus early, they will often become extremely dwarfed, may produce excess tillers, and the leaves will have a more erect habit. If infection is severe, it may result in yield losses.
So whilst out looking for tan spot, it's a good idea to check for those aphids too!