Iowa Field Reports: Drought Stress, Herbicide Injury, Soybean Gall Midge

Corn leaf rolling due to moisture stress. Photo: Rebecca Vittetoe, Iowa State University

Limited rainfall and the warmer temperatures causing crop stress, herbicide injury in soybeans, soybean gall midge, and Japanese beetles were some of the common issues or concerns that ISU Extension field agronomists saw in fields across the state this last week. Read on to see what’s happening in specific regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “In the NW corner of Iowa we have a mixed bag. Along the west edge we have counties about 5 inches of precipitation or more below normal since April 20. Recent rainfall has been spotty, but it seems to miss the areas the need it the most.

“Rolled corn, stressed beans, and bleached out patches where sandy soils occur can be seen in those areas. Still thankful we started with a full soil moisture profile or it could be a lot worse. Like most summers, rainfall is spotty. However, over half the area is within about an inch of normal and looks quite good.

“Tassels are starting to emerge, beans are fully blooming, and some are showing recovery from the herbicide injury they had. It was easier to find gall midge this past week, but I have not observed it killing plants yet. Stalk borers along field edges were causing more problems so far.”

Paul Kassel (Region 2): “Corn and soybean continue to look good across the area.  Corn is at the V14 stage. You can easily unroll a few leaves and find the tassel. We are starting to see a few tassels near farmsteads and other protected areas. Off-target movement of dicamba products is fairly widespread in many Enlist, Liberty Link or conventional soybean fields.

“The dicamba drift injury symptoms began to appear around June 20 and have persisted since.  These affected fields will often have 5-6 nodes with leaves that show the classic dicamba injury symptoms. Unfortunately, many of these dicamba affected fields do not appear to be recovering from this injury very quickly.

“Dicamba off target movement from dicamba treated corn fields as well as dicamba treated soybean fields is the suspected source.”

North Central Iowa

Angie Rieck-Hinz (Region 3): “Most areas across NC Iowa received no rain; however, Northwood did receive 0.84 inches of rain this past week. Stress from hot temperatures and lack of rain is becoming more evident. Other than field calls looking at off-target movement of herbicides and weed control failures, there appear to be few other issues of concern.

“I have seen a few corn tassels, and beans are rapidly approaching R3. The cutting of the second hay crop has started here in NC Iowa.”

Northeast Iowa

Terry Basol (Region 4): “Rainfall this past week was non-existent for the area, but luckily our subsoil moisture has helped sustain the crops through the warm dry weather conditions so far. The crops could definitely use a drink in the next week to help offset the heat and water usage from the weather conditions last week and this week.

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Corn is anywhere from V12 to V14, and I expect it to be at VT (tasseling) within the next couple of weeks. Overall, continue to scout and monitor for foliar diseases and begin to look for corn rootworm feeding in continuous corn fields as well as those with a history of Bt performance challenges.

“Soybeans have entered the R1 stage (one open flower at any node on the main stem). Postemergence herbicide applications are primarily wrapped up in soybeans for the area. We have seen a fair amount of non-dicamba tolerant soybean leaf cupping across the state due to drift and or volatilization of dicamba based products labeled for both corn and soybeans.

“Second cutting of hay is underway for most of the area as well.”

Central Iowa

Meaghan Anderson (Region 7): “Central Iowa had another hot and dry week with almost all of the area receiving no rainfall. Early last week, corn was in the late vegetative stages and holding on really well despite the dry conditions, but some fields were beginning to show significant stress in light soils and areas with poor rooting by July 4.

“Some fields are beginning to tassel and show silks, so I am holding out hope for good rainfall and relief from the heat during this critical stage of development. As has been the usual lately, most of my time is spent walking soybean fields that are in the R2 and R3 growth stage with herbicide injury symptoms.

“While many fields look healthy and have closed rows, non-dicamba-tolerant fields are easy to spot on the landscape. Central Iowa farmers will want to keep an eye out for soybean gall midge in their soybeans, Japanese beetles in both corn and soybean, and corn rootworm injury to roots in corn fields in the next couple weeks.”

Southwest

Aaron Saeugling (Region 10): “Corn looks good despite the dry conditions across most of my region. We could definitely use a nice rain. Areas that are showing signs of stress the most due to the hot and dry conditions are the continuous corn fields or parts of corn fields with thinner soil types. I expect corn to be tasseling soon.

“On the soybean side of things, I’ve been seeing more insect pressure, particularly Japanese beetles in soybeans this past week. Additionally, on the soybean front, fields with 30” rows have yet to canopy, which is causing weed control challenges.

“The hot and dry weather is also taking its toll on forages with more reports of poor hay conditions. Alfalfa that had winter-injury has been really slow at growing back after the first cutting.”

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “The past week brought drier and warmer conditions across EC Iowa. Corn is getting close to tasseling with some fields already showing tassels. Soybeans are mostly R2. In general, the crops are looking good.

“I’ve been seeing little disease pressure outside of a few reports of bacterial leaf streak in corn, and on the insect side I’ve mainly seen Japanese beetles and some grasshoppers this past week. Continue to scout fields for disease or insect issues.

“The main concern or issue I had this past week was herbicide injury in soybeans, particularly injury due to a growth regulator or group 4 herbicide. I’ve had lots of comments and questions about how widespread the injury appears to be in soybean fields this year.

“Farmers with wheat have started harvesting it, and the second cutting of hay is also underway.”

Virgil Schmitt (Region 9): “Rainfall last week was variable in the counties I cover, ranging from less than 0.5 inch roughly north of I-80 to between 0.5 and 2.5 inches roughly south of I-80, with locally heavier or lesser rains.

“In general, temperatures last week in the counties I cover were above normal, with temperatures being more above normal in the northern counties compared to the southern counties. Second cutting hay harvest is in full swing and should be mostly complete by the end of the week.

“Most corn fields range from V14 to V16 and look good. Plants are showing stress in areas where soil moisture is limiting or where root function is compromised. Soybeans are mostly R2. In general, they also look good, but some fields are also showing (lack of) moisture stress.

“Supplemental nitrogen applications to corn, herbicide drift, herbicide injury (mostly tank contamination), potato leafhopper management in alfalfa (commonly alfalfa seeded with oats to be harvested for grain), and Japanese beetles were common topics of discussion last week.”

Josh Michel (Region 11): “Over the past week scattered showers delivered anywhere from about 0.25 to 0.50 inch of precipitation across much of SC Iowa. Areas in SE Iowa on the other hand, received 1 to 2 inches, with some isolated areas receiving up to 6 inches of rainfall.

“With continued limited amounts of rainfall and above average temperatures, pastures and alfalfa fields in many areas are showing signs of stress. Second cutting of alfalfa is well under way and completed in some areas. I’ve been hearing reports of lower than average yields and severe insect feeding in some areas.

“Despite limited moisture in some areas, corn is continuing to grow quickly. In general, the corn looks good and most fields are around V12 to V14. In some early planted fields tassels may be visible by the end of the week. With the limited rainfall and higher temperatures, some corn fields have shown signs of stress with leaf rolling.

“Soybeans are V5 to R1, with some fields reaching R2 later this week. Most of my soybean related field calls continue to be centered around herbicide injury, herbicide drift, and insect feeding. There is also increasing concern that some soybean fields may not reach full canopy closure, which could allow for an above average number of later-season weed escapes.”




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