Welcome to another season of weekly small grains disease and pest updates. This first issue should have gone out last Friday after the scouts completed their first week roaming the Minnesota countryside looking for diseases and pests. Unfortunately, a technical glitch prevented me from seeing the tally of their work. So....here it goes.
Diseases
Overall, the disease situation is relatively quiet. All indications are that stripe and leaf rust pressure in Kansas and Nebraska is relatively low. That means that the number of spores traveling north will also be low. This, in combination with the unfavorable weather conditions (as indicated by the NDSU disease risk models), suggests that things will continue to be quiet for those two diseases. To date, the weather has been most favorable for tan spot. The scouts found a few tan spot lesions in three of the sixty fields in west central and northwest Minnesota. The previous crop was spring wheat in each instance. Crown rust has been confirmed in southeast Minnesota, but incidence and severity were very low.
Last week, the risk models for FHB indicated low risk across the state. Today and until the end of the week, the western half of the state will remain at a low risk. Only along the Wisconsin border does the risk increase to moderate when selecting the option to calculate the risk for very susceptible spring wheat varieties. The oat crop in southern Minnesota is reaching the heading stage. An application of propiconazole at Feekes 10.5 on oat varieties rated 5 or worse for crown rust will likely pay. While there is some risk for FHB to develop in the next couple of days, the models indicate that the risk is waning before the end of this week.
Insects
Aphids have been found across most of Minnesota. The numbers to date have been low, but transmission of BYDV has been observed, with some reports of individual plants showing not only the typical yellow or red discoloration of the leaves but also some stunting. The old threshold for controlling aphids in wheat, barley, and oats was to control aphids once 80% of the stems across the field had one or more aphids before heading. NDSU updated its threshold for controlling aphids in small grains. The updated recommendations can be found in the North Dakota Field Crop Insect Management Guide. The scouts also found one cereal leaf beetle (CLB) in Pennington County. This is the third consecutive year that CLB has been found in Minnesota. This suggests that this pest is now a permanent resident. A follow-up article on how to manage CLB will be forthcoming.
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