Iowa Field Reports: Planting Winds Down, on to Weed Challenges

Lots of little waterhemp plants showing up in a soybean field. Photo: Meaghan Anderson, Iowa State University

With planting (and replanting) starting to wind down, farmers are turning their attention to post herbicide applications, sidedressing, and putting up hay. Weed management challenges and thistle caterpillars in soybeans have been some of the big issues across the state this past week. Check out what Iowa State University Extension and Outreach field agronomists are seeing and hearing in fields from their respective regions across the state.

Northwest Iowa

Paul Kassel (Region 2): “There was a lot of progress on field work last week. Many farmers completed post-emergence herbicide applications on corn. Herbicide application was needed as many corn fields had a lot of waterhemp, which was developing rapidly. There was a lot of corn that was planted the first week of June, which has emerged and is looking good. Soybean planting is mostly complete. There are a few areas (mostly in Dickinson and Emmet Counties) left to be planted that are still on the wet side. I’m also seeing thistle caterpillars in soybean fields.”

North Central Iowa

Angie Rieck-Hinz (Region 3): “In the counties I cover, we received 0.2 to 4 inches of rain on Saturday (June 15) afternoon/evening. Some of that rain came with high wind that flattened corn. That corn is expected to recover. Things I saw in the field this past week included variegated cutworms, urea burn on corn leaves, and soybeans planted the last week of May through the first week in June are still struggling to emerge. Corn is from V1 to V7 and soybeans are VE to V4.

“Weed control from pre-emerge herbicides is starting to break and a lot of post-applied herbicide action was happening in corn. Some of those later planted soybeans were planted “naked” which puts a lot of pressure on weed control for those post-applied herbicides.”

Central Iowa

Meaghan Anderson): “Much of central Iowa got a welcome rain (ranging from almost nothing to over 2 inches) over the weekend after a dry week to finish out planting, replanting, spraying, and other field work. Some areas had high winds and I heard a few reports of small hail that caused some tattering of row crops. Most corn is now in the V5 to V7 stage and just getting out of the ‘ugly duckling’ stages; some is still yellow and uneven looking, often relating back to compaction, water, nitrogen, or a combination of these.

“While some soybeans are still just emerging, earlier planted fields are in the mid vegetative stages and will very soon be flowering.  Soybean insects have been a plenty this spring, with thistle caterpillars showing up in droves unlike anything I’ve ever seen. Phone calls really picked up in the last week with questions about covers for prevented plant fields, controlling large weeds, and herbicide drift being the most common.”

Southwest and West Central

Aaron Saeugling (Region 6): “The early planted corn is V8, with most corn in the V3 to V7 range. Corn is contacting nitrogen and is looking good. Soybeans on the other hand are more challenging with pockets of thistle caterpillars causing leaf defoliation. Weeds are challenging applicators with windy conditions and weed size. First crop hay looks to be good and was baled with little rain damage.”

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “Over the past week the counties I serve saw anywhere from 0.5 inch to 2 or more inches of rainfall, with most of that coming on Saturday, June 15. With the rain, there have been some isolated reports of small hail that caused some tattering in crops, but they should recover just fine.

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“Corn mostly ranges from V2 to V8 and soybeans mostly range from V1 to V3. I did see my first flower on a soybean plant on Monday (June 17). Questions over the past week included cover crop options with prevented plant fields, nitrogen considerations this spring, bean leaf beetles, thistle caterpillars, and weed management considerations.”

Virgil Schmitt (Region 9): “Rainfall this last week has been from less than 0.5 inch to over 2 inches, with most of it coming on Saturday, June 15. There was some tornado damage on the eastern Des Moines – Louisa county line. Most people had about four days of field work conditions. Corn planting has mostly ended.

“April planted corn is V7 ro V8, mid-May planted corn is mostly V5 to V6, and June planted corn is mostly V1. Many fields are very uneven. Soybeans are from V3 down to still in the bag. Soybean planting is about 85% complete. Inquiries about corn maturities, herbicides, and cover crops dominated calls last week. I’m noting more dead smooth brome heads than usual due to stalk borers.”

Josh Michel (Region 11): “Field operations continued throughout much of last week. Scattered rainfall across the region brought a 0.1 to 0.5 inches of rain, with a few isolated areas seeing up to 1 inch. Corn is around 80 to 85% planted, and soybeans are about 60 to 65% planted. Corn ranges from V7 for the early planted corn to VE. Earlier planted soybeans are V3 to V4. Recently planted soybeans have been having some emergence issues.

“Bean leaf beetles and thistle caterpillars are causing some minor concerns with soybean feeding. Harvest from first cutting in alfalfa fields has been completed. Common questions this past week have been on nitrogen management, bean leaf beetle feeding, late season weed management, as well as Prevented Planting options.”


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