Tamra Jackson-Ziems, NE Extension Plant Pathologist
Bacterial Leaf Streak
Grower reports and samples submitted to the Plant and Pest Diagnostic Clinic indicate bacterial leaf streak is increasing in corn. This week it was confirmed in Box Butte, Scotts Bluff, and Kimball counties and has now been confirmed in 70 counties. A survey is underway to collect samples from western Nebraska counties where it hasn’t been confirmed.
Southern rust was confirmed in three more counties this week: Phelps, Howard, and Otoe, making a total of 12 counties in eastern Nebraska where it’s been found. To follow movement of Southern rust in Nebraska and other states, view the map at http://ext.ipipe.org/
Given the economics of a fungicide application and low corn prices, an application is generally not recommended at this point in the season unless there is a major flare-up in a given field, or if the field was planted very late and is earlier in development and more vulnerable to disease.
Gray leaf spot is also being reported in corn.
Frogeye Leaf Spot
Reports of phytophthora and Frogeye leaf spot continue in soybean. If you apply a fungicide for control of Frogeye leaf spot and do not get the control you expect and suspect resistance to fungicides, please send samples to the university’s Plant and Pest Diagnostic Clinic and indicate the sample is for Frogeye research. Please indicate the fungicide applied, application rate, and date applied. Fungicide resistance has been documented in the Bootheel of Missouri and in eastern Iowa.
For more information on individual diseases of corn and soybean, see Plant Disease Management for Agricultural Crops in CropWatch… https://cropwatch.unl.edu/plantdisease.