Iowa Field Reports: Herbicide Drift, “Rapid Growth Syndrome,” Short Soybeans

    Example of twisted whorl or buggy whip. Corn pictured here has mostly grown out of the twisted whorls. Photo: Ethan Carter, University of Florida

    Spotty rainfall across the state, herbicide drift, “Rapid Growth Syndrome” in corn, and shorter beans were common issues or concerns that ISU Extension Field Agronomists saw and heard about this past week. Read on for more specifics about what’s happening in different regions across the state.

    Northwest Iowa

    Paul Kassel (Region 2): “Farmers and commercial applicators are completing herbicide applications on the soybean crop. A period of windy weather last week was followed by some good conditions for herbicide applications this week. The corn crop is at the V8 stage.

    “Most field operations on corn are wrapping up as many farmers have complete their planned sidedress nitrogen applications. The next decision on the corn crop will be fungicide use. As a general topic, there is concern on the future of postemergence herbicide traits and products for soybean.

    “The recent legal action on dicamba use in the soybean crop has many farmers pondering their options for next year. While dicamba has it issues, it is another tool to manage difficult to control waterhemp, marestail and giant ragweed.

    “Additionally, farmers and applicators have observed a lack of performance from fomesafen (i.e. Flexstar) products on waterhemp, and they do not like the leaf burn/crop response from fomesafen products.”

    North Central Iowa

    Angie Rieck-Hinz (Region 3): “Rainfall for the week of June 15 to 22 was 0.29 inches at Rockwell City to 4.51 inches at Hampton.  While there was a lot of rain around Hampton, it has brought the April 1 to June 22 rainfall total to be more in line of “normal” for that time period.

    “The Iowa Environmental Mesonet report for Fort Dodge still shows rainfall is 4.69 inches below average for the April 1 to June 22 time period. This lack of moisture has been evident in fields in that area as I have seen crops showing signs of stress.  Several locations in my area also experienced damaging hail on Sunday, June 21.

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    “Corn is mainly V8 to V11, and every soybean field I was in last week was R1 or beginning bloom. The story of the past week has been herbicide issues including drift, off-target movement, tank contamination, and wrong products applied.

    Generally speaking, insect pressure is low, although the stalk borers have already moved into the outer rows of corn.  I also found thistle caterpillars as far north as Belmond, which as far north as I have seen them this year.”

    Southwest

    Aaron Saeugling (Region 10): “A majority of SW Iowa missed out on any measurable precipitation last week. Cass County and portions of Pottawattamie County are around five inches below average for precipitation this growing season. Painted lady butterflies are abundant in the countryside, so expect more pressure from thistle caterpillar larvae in the weeks to come.

    “Corn generally looks very good across SW Iowa, and most corn is V8 to V12 depending on planting date.  Soybeans are on the other end of the spectrum with some fields showing more environmental stress.  In general, while soybeans are starting to flower, they are also shorter than average.

    “Additionally, I’m seeing a variety of insect pressure in soybeans. While insect pressure is not severe, it is something to keep an eye on. Second crop alfalfa looks to be coming along nicely; however, expect lower tonnage but good quality with the second crop alfalfa.  Pastures are doing ok despite the dry weather.”

    East Central, Southeast, and South Central

    Rebecca Vittetoe (Region 8): “Rainfall this past week ranged anywhere from 0.5 to 3 plus inches of rainfall across EC Iowa. Corn ranges from V8 to V11, and most soybeans are now at R1. Corn is really starting to stretch and overall looks pretty good.

    “A few days last week you could see corn leaves starting to roll in some fields. Additionally, over the weekend, I started to get reports of bacterial leaf streak showing up in corn fields. This is a fairly new disease corn disease in Iowa that can be mistaken for gray leaf spot or other disorders.

    “Common questions or issues on the soybean side this past week included herbicide drift, herbicide injury, and concerns about short or stunted soybeans.”

    Virgil Schmitt (Region 9): “Rainfall last week was variable in the counties I cover, ranging from less than 0.5 inch up to 1 inch, with locally heavier rains. In general, temperatures last week in the counties I cover were near normal. First cutting hay harvest is nearly complete.

    “Most corn fields are at V9 to V11 and look good. “Rapid Growth Syndrome” (twisted whorls and yellow “flag” leaves) is continuing to be seen as well as uneven corn continues to be a concern. Some corn is starting to “roll” due to heat and lack of rainfall in areas.

    “Soybeans are mostly V3 to R1. In general, they also look good. Herbicide injury, herbicide drift, uneven corn, and “rapid growth syndrome” dominated calls last week.”

    Josh Michel (Region 11): “Scattered precipitation fell across much of the region over the last week. Many areas in SC Iowa received 0.5 to 1 inch of rainfall, while isolated areas farther east received up to 3 inches of rainfall.

    “Corn is growing quickly, and many fields are generally around V8 to V9. Some fields have begun to show some signs of dryness with leaf rolling, especially in areas that are lower on moisture. I’ve also had inquiries about rapid growth syndrome in corn.

    “Soybeans are generally around V4, with some fields beginning flower (R1). Most of my soybean related field calls have consisted of herbicide injury, herbicide drift and insect feeding. There has also been some concern and discussion about some soybean fields not achieving average height for this time of year as well as potentially not reaching full canopy closure.”




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