Regional Update: June 19 – 27, 2023

While some much needed and welcomed rain fell across most of the state this past week, some areas received minimal to no rain. The dry conditions, herbicide injury, potato leafhoppers, nutrient deficiencies (mainly potassium), weed control failures, and tar spot are some of the highlights on the issues or questions ISU Extension and Outreach Field Agronomists heard about or received this past week. Read on for more specifics about what’s happening around the state.

Northwest Iowa

Leah Ten Napel (Region 1): “In NW Iowa corn is staging V7 to V12. We are seeing entire corn fields rolling leaves early in the day due to heat and moisture stress. Soybeans are ranging from early to late vegetative state, with flowering right around the corner. Post applications of soybean herbicide are mostly finished up across the region. Corn and soybean plants are appearing very short for this time of year. Although soybean plants are bushing out, there is the concern about not closing the canopy soon enough due to their short stature. Calls have been coming in on herbicide injury, but many of these symptoms will pass. Insects are starting to cause issues, grasshoppers being the main concern I am hearing. Before applying insecticide, scout your field to see if you are reaching the economic threshold to spray. Read this Purdue article on grasshoppers to learn more. Pastures and hay fields are relying on rainfall for regrowth, and we are starting to see insect pressures in those fields as well.”

Gentry Sorenson (Region 2) “Needed rainfall occurred through the weekend across the area. Rainfall ranged from under an inch to close to two inches. Post emergence applications of herbicide to soybeans to control broadleaf and grass was being made last week before the rainfall. Soybeans range from V6 to R1 and corn ranges from V9 to V11. Before the rain corn was showing signs of moisture stress in some counties that have been short of rainfall.  IDC (Iron Deficiency Chlorosis) is present in some soybean fields with high pH areas. Most phone calls and farm visits include questions on herbicide carryover, herbicide drift, plant growth regulator damage to soybeans, sulfur deficiency in corn, and questions about tar spot.” 

Northeast Iowa

Josh Michel (Region 5): “Most of NE Iowa received some much-needed rainfall over the past weekend. Generally, most of the area received 0.50 to 1 inch, but a few isolated areas were able to receive up to 2 inches. This was very welcomed as many crops have been showing signs of moisture stress over the past two to three weeks. The latest drought monitor shows most of NE Iowa in a D1 to D2 status. Most corn fields are currently around V7 to V9. Post herbicide and side dressing applications are finishing up. I’ve also been seeing some nutrient deficiencies, but this is likely due to the dry conditions. Soybeans are generally around V3 to R1, with many post herbicide applications finishing up. There are some continued concerns about soybeans planted on 30 inch rows not reaching canopy closure. Oats are mostly headed out. Alfalfa regrowth continues to be a concern as insect pest pressure, mainly armyworms and potato leafhoppers, continues to be a scouting priority. Second cutting has started in some areas, while producers in others are cautiously waiting. Pastures across most of the region have significantly slowed down due to moisture stress and warming temperatures, with some having gone dormant. Other field calls for the week centered around herbicide applications and injuries, weed identification and management, forage management, as well as crop assessments related to the drought.”

Central Iowa

Meaghan Anderson (Region 7): “Much of central Iowa was shorted on the rainfall totals this week, with only the fringes of my area receiving much more than 0.25 inch of rain. It looks like the forecast holds some good chances for us to catch something in the next week, which will help keep these crops growing as they reach peak water usage time! Corn is growing quickly, with most fields past V10 and putting on a new leaf every couple days. I spotted my first corn rootworm pupa in Dallas County last week, so we’ll be sure to see adults emerging sooner than we’d like; now is a great time to dig roots and look for feeding. The big news in central Iowa corn fields this week is that tar spot was discovered for the first time this growing season in several of my counties, including Story, Polk, Marshall, and Jasper. While the finds were small, it was yet another reminder that we don’t fully understand this pathogen and its development in corn. Soybeans are in the V4 to R1 growth stage across most of central Iowa. The continued phone calls about weed control failures provide encouragement that people are scouting fields after application, but I’m dismayed at how many people are having trouble controlling waterhemp in both corn and soybean this year. Other phone calls have been about pasture management, nutrient deficiency symptoms, and spray drift.”

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “Rainfall totals were again variable across EC Iowa with some areas receiving a tenth or less and other areas receiving 0.5 inch to 2 inches. You can tell the neighborhoods that have been fortunate to have received more rain this year compared to the ones that seem to continue to miss the rains. There were some tough looking fields late last week and on Saturday with the warmer temperatures. Most corn fields have surpassed the V10 stage and soybeans are mainly V4 to R1. Tar spot has been observed in a few fields in more central Iowa this last week for the first time this year. In my region, it was observed at very low levels in a field in Poweshiek County. Forages have really slowed down, and I started to see more potato leaf hopper pressure in alfalfa fields over the last week. Folks have started taking second cutting alfalfa. Other concerns or issues this past week have been on weed control failures, potassium deficiencies in corn and soybean fields, and herbicide injury (drift and carryover).”

Virgil Schmitt (Region 9): “Rainfall in the last week in the counties I cover ranged from less than 0.05 inch to over 1.50 inches, with lesser amounts generally south of Highway 92 and the heaviest amounts generally along Highway 38 north of Interstate 80. Rainfall continues to be very hit-and-miss. Shallow-rooted grasses, such a bluegrass continue to go dormant in many places. Second cutting hay is well under way. It appears this will be a below average harvest in terms of quantity, but quality should be good. Some alfalfa fields have high populations of potato leafhoppers. I received a couple of calls from people who had a new alfalfa seeding under an oats cover crop and had very poor stands of alfalfa. People are wondering if the seed germinated and ran out of moisture or if it did not even germinate and is waiting for moisture. Most corn is V9 to V10  and looks good to excellent  except in areas of coarse soils, clay soils, and compacted areas. The heat of last Saturday caused corn on even very good soils to start to roll their leaves. Questions about UAN left on the surface with applications after the May 8 rainfall event continue to come in. People are wondering how much was lost and if dribbling on more UAN is warranted. Most soybeans are V5 to R2 and also look good to excellent except for areas of coarse soils, clay soils, compacted areas, and areas where crusting issues have lowered populations. Phone calls, emails, and field visits last week mostly involved sulfur and potassium deficiency symptoms in corn, compaction issues in corn, supplemental nitrogen for fields where UAN was left on the surface, and armyworms in pastures and grass hay.”

Clarabell Probasco (Region 11): “Rainfall over the last week was again the story of the have and have not's for the area. Those that were fortunate enough to receive rainfall typically only got a few tenths at most out of the systems. The U.S. Drought Monitor updated the drought zones to a D3 (extreme drought) for all of Davis, most of Appanoose, and then some of Van Buren, Wayne, and Wapello counties. The rest of the counties in south central Iowa remain in the D2 (severe drought) and D1 (moderate drought) zones. Corn and soybean fields are both continuing to show stress from the lack of moisture, especially in areas with thinner soils and less subsoil moisture to pull from. Soybean fields are continuing to be found flowering in certain areas and are beginning to branch heavily to help compensate for the shorter plant height. Hay harvest has begun wrapping up for many producers while second cutting alfalfa is taking place for those that have received enough regrowth. For most producers, forage quality has been good, but tonnage has been lacking compared to typical years. Japanese beetles, stink bugs, and grasshoppers are beginning to be seen here and there in crop fields. Pastures are in large need of moisture and forage supply is diminishing for some. Most field calls have been regarding the drought stress being noted on crop fields.”

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