Regional Crop Update: June 22- June 30, 2020

June 30, 2020 10:38 PM
Blog Post

Lack of moisture in the western part of the state to excess moisture in the eastern part of the state, herbicide injury in soybeans, and bacterial leaf streak in corn were the common issues or concerns that ISU Extension field agronomists saw and heard about this past week. Read on to see what’s happening in specific regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “In the NW corner we have four counties, Monona, Woodbury, Plymouth and Sioux, with weather stations reporting about half of normal rainfall since April 20. These counties about 4 or more inches behind their normal rainfall. The other five counties I cover away from the South Dakota border are only about an inch behind normal rainfall. I am grateful that the subsoil profile was full and roots for most fields are in that reserve. Most cornfields appear to be V10 to V12 and look very good. Blooms can be found in almost all soybean fields with some fields reaching R2. A couple of hail areas caused quite a bit of damage a week ago, but most recent calls involve off-site herbicide injury. Seeing soybean leaves cupping is not an uncommon occurrence right now, in my opinion.”

Paul Kassel (Region 2): “Crop development continues at a rapid pace across the area. Corn is at the V12 stage, and you can easily unroll six leaves and find the tassel. We should start to see a few tassels emerge in about two weeks. The soybean crop is developing rapidly as well. Post emergence herbicide applications on the soybean crop are nearing completion. There have been a few performance issues with Xtendimax/Engenia/Fexapan on waterhemp, and consequently a few fields will get retreated. Additionally, there have been cases, sometime fairly severe, where off-target movement of dicamba has injured non-Roundup Ready Xtend soybean varieties.”

Dicamba drift injury to a Liberty Link GT27 variety in a Kossuth County soybean field. Photo courtesy of Paul Kassel.

North Central Iowa

Angie Rieck-Hinz (Region 3): “During the week of June 22 through June 29 rainfall was spotty. Hampton received 3.72 inches of rain (Iowa Mesonet), and Humboldt received 0.92 inches of rain. Humboldt, Webster and parts of Calhoun County remain on the drier side with below normal rainfall. Humboldt is currently 5.82 inches below average for April 1 through June 29. Corn is V10 to V14, and the majority of soybean are R1 to R2. I have spent most of my time on herbicide complaint calls with the majority of those being soybeans experiencing off-target movement of growth regulator or Group 4 herbicides. It so ubiquitous in some areas that it really is discouraging. Entire soybean fields are showing cupped leaves. I have seen no disease in corn to date, although there have been some reports of bacterial leaf streak in corn in NC Iowa.”  

Growth regulator or herbicide group 4 injury has been a common issue observed in many NC Iowa soybean fields. Photo courtesy of Meaghan Anderson.

Northeast Iowa

Terry Basol (Region 4): “Corn and soybeans continue to look good here in NE Iowa. Growing conditions have been very conducive for corn development, and the corn ranges from V8 to V9, with some isolated areas slightly further ahead. Sidedress nitrogen and herbicide applications are pretty well completed, with canopy row closure occurring in most of the territory.  We will certainly be at corn heights higher than “knee high on the Fourth of July” this year. While the growing season may have started off cool and behind on Growing Degree Days (GDDs), we’ve caught up to normal accumulated GDDs for this time of year. Soybeans continue to do well and range from V4 to V5 within the area. Field operations have primarily consisted of postemergence herbicide applications within the last couple of weeks. Here is a nice review on spraying dicamba products labeled for over-the-top application in soybean. Also, to learn more about temperature inversions and the potential for off-target drift here. In regards to precipitation, we’ve been pretty lucky (maybe too much so with flash flooding in some areas) to receive ample rainfall for the area. According to the Iowa Mesonet, the NE Iowa Research and Demonstration Farm near Nashua received a total of 3.11 inches of rain from June 20 through June 29 and has had a total of 6.69 inches for the month of June.”  

Growing Degree Day (GDD) accumulation for the NE Iowa Research and Demonstration from from May 1 through June 30. Source: ISU Environmental Mesonet.

Central Iowa

Meaghan Anderson (Region 7): “Central Iowa is divided by a dramatic difference in rainfall since planting started, with most of the area less than 75% of normal since then and less than 50% of normal since June 1. Several counties are regularly making an appearance on the drought monitor. Both corn and soybeans are showing signs of stress in the lighter soils and areas of poor root development. The eastern fringes of my area (Warren, Jasper, Marshall, Tama Co) have certainly not suffered from too little rain, with some areas more than 200% of normal since June 1. The forecast looks to keep this the status quo for this week, but we’ll hope for some temperature relief, rainfall for the western reaches, and a break for the east. Most corn is past V12, which means the potential kernel numbers are likely set (or nearly so), and conditions during pollination and early reproductive stages will decide how many kernels develop. I’ve seen very little sign of disease development, but continued scouting prior to a fungicide application is important. Common corn issues include potassium deficiency, sulfur deficiency symptoms, and root pruning from corn rootworms. Soybeans are mostly in the R2 growth stage, and some narrow rows are beginning to shade the row. Herbicide injury has been the most common issue in soybean fields, with carryover, misapplication, and drift all showing up across central Iowa; it seems the high temperatures and strong winds in June were not good for applications. We’ll be keeping an eye out in crop fields for disease issues and insect problems like Japanese beetles, thistle caterpillars, and corn rootworms in the coming weeks.”

Percent of normal rainfall across the state of Iowa for the month of June. Source: Iowa Environmental Mesonet.

East Central, Southeast, and South Central

Rebecca Vittetoe (Region 8): “While some parts of the state have missed out on the rain, rainfall across EC Iowa this last week as ranged from 1 inch to some isolated areas receiving closer to 6 inches. Corn mostly ranges from V9 to V12. Outside of the wet areas in some fields, the corn is looking pretty good. I’ve had a few more reports of bacterial leaf streak (BLS) showing up in corn fields; however, I have also seen more physical injury to corn leaves that has been mistaken for BLS. As a reminder, BLS will appear as long, thin pale orange to brown streaks on corn leaves. If you suspect you might be seeing BLS, hold the leaves up to the light and they should “pop” as they will be surrounded by light yellow halos. Most soybean fields are at least at R1 if not at R2. There was a lot of post-emergence herbicide applications made in soybeans this last week. The biggest issues I saw in soybean fields this last week was related to herbicide injury.”

Example of physical injury on a corn leaf that has been mistaken to be BLS. Photo courtesy of Rebecca Vittetoe.

BLS causes long, thin pale orange to brown streaks on corn leaves, and when you hold the leaves up to the light, the streaks “pop” and are surrounded by light yellow halos. Photo courtesy of Crop Protection Network.

Virgil Schmitt (Region 9): “Rainfall last week was variable in the counties I cover, ranging from less than 0.5 inch in southern Lee County up to 2.5 inches elsewhere, with locally heavier rains. In general, temperatures last week in the counties I cover were near normal to three degrees below normal. Most corn fields are at V11 to V13 and look good. Sulfur deficiency symptoms are an issue in some low organic matter soils without a recent history of manure applications and in wet areas.  Soybeans are mostly R2, and in general they also look good. Sulfur deficiency in corn, herbicide injury, herbicide drift, and herbicide misapplications dominated calls last week.”



Josh Michel (Region 11): “Similar to last week, scattered precipitation fell across much of my region. Many areas in SC Iowa received 0.5 to 1 inch of rainfall, while isolated areas farther east in my area received up to 3 inches of rainfall. With limited amounts of rainfall and increasing temperatures, pastures and alfalfa fields have experienced limited growth. Corn continues to grow very quickly, and many fields are generally around V10 to V11. Some fields have shown signs of dryness with leaf rolling, especially in the areas that are lower on moisture. Soybeans are generally around V4 to V5, with many fields beginning to flower (R1). Most of my soybean related field calls have centered around herbicide injury, herbicide drift, and insect feeding. There has also been some increasing concern regarding some soybean fields that may not achieve average height for this time of year and potentially not reaching full canopy closure.”

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!



Rebecca Vittetoe Field Agronomist in EC Iowa

Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...