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Observations from the Field
I am keeping my fingers crossed that nothing "weird" pops up in the next month, but here is a synopsis of things I am seeing or hearing about right now.
Corn is primarily R4 to R5 and the majority of soybeans are at R5 (beginning seed). Most fungicide applications are now complete.
Corn Diseases: Tar spot- yes, it is out there. There are definitely hybrid differences and differences by location based on rainfall. In places that had significant rain two weeks ago this disease is increasing in incidence and severity. Can we out run tar spot at this growth stage? We have limited data on fungicide timings post R1 and in discussions with Alison Robertson, our ISU corn pathologist and Darcy Telenko from Purdue this last week, Dr. Telenko stated that R4&5 applications have not done well in reducing disease. Gray leaf spot is fairly easy to find, but I have not found anything severe and Northern Corn Leaf Blight and Common rust are also present.
Corn Insects: Grasshoppers, and of course corn rootworm beetles, are present in fields. For those of you trapping CRW adults, what are you seeing? I feel like numbers are lower this year, but this is based on counts I receive from a few people. Curious as to what you are experiencing? This week I received several phone calls and texts about aphids in corn. Generally speaking we can find several species of aphids in corn, but they are usually not a problem and tend to be found more along field edges. Since we are past pollination they won't interfere with pollination, but if numbers are high enough the honeydew can cause sooty mold that will interfere with photosynthesis. There are no treatment thresholds for aphids in corn, but this article provides points to consider before you think about an insecticide application.
Soybean Diseases: I have seen Bacterial blight, Septoria brown spot, and Frogeye leaf spot in soybeans, this is not at all unusual. I also found Sudden death syndrome just beginning in a few fields.
Soybean insects: I have yet to find any soybean aphids, but I have had a few phone calls about really low numbers in scattered fields. There are spider mites in places that have been dry and now we need to think about Soybean gall midge in North Central Iowa. On Wednesday, August 3, Soybean gall midge was confirmed in Kossuth, Humboldt and Webster Counties. Additional locations confirmed in Iowa in 2022 include Polk, Warren, Palo Alto and Pocahontas counties.
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Events
August 17 at 10 a.m., ISU Central Iowa Field Agronomist, Meaghan Anderson is hosting a Hail and Crop Damage Meeting at Wildeboer Farm Bin Site on the north side of Zearing in response to the hail damage incurred on Thursday, August 11th. This meeting is open to all and there is no need to register.
August 23. Virtual Drought Webinar. Rainfall across Iowa has been very erratic this year with wide swaths of areas showing up in varying categories on the drought monitor. ISU Extension and Outreach will host a virtual drought meeting for those who are interested in attending and looking for resources. A face-to-face meeting will be held in Knoxville on August 24th. Click here for more information about the webinar or live meeting.
September 8. The Northern Research Farm will host the annual fall field day starting at 9 a.m. with refreshments and field tours starting at 9:30. Check out the graphic below for speakers. Please RSVP to the Wright County Extension office by September 2 by calling 515-532-3453 to be included for lunch.
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