Small Grains Disease Update 06/22/2020
Little changed in both the risk models or reports that I received this past week. I suspect there is some stripe rust and crown rust here and there across the southern half of the state, while tan spot is probably the only fungal disease you might find in the northern half of the state as of today.
That is likely to change in the near future as much needed rain fell across much of the state when a couple of cold fronts brought relief from the blast-furnace heat and wind of the first half of last week. While the risk of leaf rust infections has already started trending higher over the weekend for all but the northeastern edge of the state, the risk of infection for FHB will start to increase by tomorrow.
The heat in the first part of last week continued to push the development of the spring wheat crop and the first spring wheat fields reached heading over the weekend in the northwest part of the state. This means that you will need to actively scout individual fields to determine the current growth stage, and locate whether you have tan spot, stripe rust, or possibly even leaf rust near the bottom, middle, or top of the canopy.
The hot windy weather itself or the herbicides applied during the hot windy weather may have caused physiological speckling or discolorations that can easily be mistaken for one of the foliar fungal diseases. Remember that tan spot, septoria, stripe, and leaf rust almost always start near the bottom of the canopy and move upwards to newer leaves as the growing season progresses. You should therefore always find worse symptoms of the same diseases lower in the canopy. Bacterial Leaf Streak (BLS) is an exception to this rule of thumb.
While your scouting you may wonder what the yield potential of the spring wheat crop is. People have already commented to me that the crop seems very short this season. I'll repost a Minnesota Crop News article about the lack of height of the crop and whether that spells disaster before grain fill even has started.
The weather forecast for the coming week looks very favorable for grain fill for winter wheat, rye, and the earliest spring wheat, barley, and oat fields as daytime highs not forecasted to exceed 85 and nighttime lows will remain in the low to mid-fifties for much of the state.
Bring your rubber boots
--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston
For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu
For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org