Regional Crop Update: May 22 - June 6, 2023

Spotty rainfall and dry conditions, replanting/filling in soybean stands, weed management/herbicide application considerations, and fertilizer burn on corn roots were some of the more common concerns or questions ISU Extension Field Agronomists received over the last two weeks. Read on for more specifics about what is happening and being seen in fields across the state.

Northwest Iowa

Leah Ten Napel (Region 1): “Although NW Iowa has received some moisture over the past couple of weeks, symptoms of dry growing conditions are very evident in many of our fields. Corn fields are being staged anywhere from V2-V5, and little insect or disease pressure is being reported at this time. Many growers across NW Iowa have had to interseed additional soybean seed into emerged fields. Soil cracking, compaction, heavy no-till residue, and furrows left open have all contributed to emergence issues this spring. There has been minimal insect and disease pressure reported in soybean fields. Alfalfa fields have been cut and baled, and many livestock herds have been turned out to pasture. Continued precipitation is needed to help these crops continue to prosper.”  

North Central Iowa

Angie Rieck-Hinz (Region 3): “Much like other areas of the state, NC Iowa is the land of haves and have nots for rainfall.  If you are lucky enough to receive a pop-up shower it could be 0.4 to 4 inches, but generally speaking we could all use a good shower to help alleviate some concerns. Corn is V1 to V7 and is many shades of green. The majority of post-applied corn herbicide spraying is done. Soybeans are VE to V2. Many of the later planted soybeans have experienced emergence issues due to dry soils inhibiting germination or severe crusting.  Iron chlorosis deficiency (IDC) is starting to rear its yellow head as well. While this seems a bit early for this issue, it can be exacerbated by dry soils. I have found a few thistle caterpillars and one seed agronomist has shared she found one as well. Don’t panic!  So far they have been few in number and far between finds.  Finally, there are some areas of suspected herbicide carryover (Group 27) on soybeans.  This should not be surprising as dry as part of the state were last year.”

Northeast Iowa

Josh Michel (Region 5): “Scattered isolated showers delivered small amounts of precipitation throughout NE Iowa over the past two weeks. Cumulatively, most of the area has received 0.25 inch or less, but some isolated areas did receive up to 0.50 inch. This lack of precipitation, along with warmer than normal temperatures has caused some early season crop concerns. Soil crusting has led to some “patching in” of soybeans in some areas, while flash-drought conditions have caused some corn fields to show signs of heat stress in areas with lighter soils. Early planted corn fields are around V4, while most fields are V2 to V3. Post herbicide applications have been ongoing over the past two weeks, while side-dressing applications are starting to take place in areas. True armyworms and black cutworms are still the main pests to scout for according to the latest Iowa Moth Trapping Network Update. Soybeans are mostly VC to V1, with some early planted fields reaching V2. Bean leaf beetles have been reported in some fields, but numbers have been low. Post emergence herbicide applications are ongoing as the weather allows. Small grains and forages continue to do well despite warm and drier conditions. Several days of dry weather and low humidity levels allowed first crop alfalfa to be harvested without any issues. Some fields were harvested earlier than planned due to increasing alfalfa weevil larvae feeding. Because of this, reported harvests were average to slightly below average tonnage, but quality seemed to be average to slightly above. There is some concern about limited or slow alfalfa regrowth due to a lack of recent precipitation. Producers should continue to scout for alfalfa weevil larvae feeding. Pastures remain in fair to good condition, with many weed escapes starting to show up and begin flowering. Oats continue to do well and are beginning to head out. Recent field calls over the past two weeks have centered around corn and soybean stand assessments, possible seedling disorders and disease, post herbicide applications and herbicide injury, alfalfa management, as well as pasture weed identification and management strategies.”

Central Iowa

Meaghan Anderson (Region 7): “Most of central Iowa received rainfall in the last week, but it ranged dramatically from nearly 4 inches to less than 0.5 inch. The spotty severe weather continues with at least one small pocket of hail in Story Co (and perhaps part of Boone Co) on June 4. The earliest planted corn is around V7 growth stage and in its rapid growth phase. These fields have evened out in color and are getting close to closing their rows. Some of the later planted corn is in the V4 growth stage and looking uneven in color while it is setting its roots. POST herbicide applications are wrapped up in corn, but I’ve been scouting after those apps and noticed some waterhemp sneaking through already. Make sure to scout fields 7-10 days after the application to evaluate control. Soybeans are mostly in the V1-V2 growth stage and POST applications are starting, so I’m hopeful for good conditions to wrap up these in a timely manner. The deadline for dicamba applications in soybean has moved up to June 12 this year. True armyworm is making its presence known again; a farmer in Story County found a very large population in a field with a heavy cover crop residue; scout fields with substantial residue to look for feeding on both corn and soybean (see 2022 article here). Field calls have been on anhydrous ammonia/fertilizer burn on corn roots, insects, and herbicide issues.”

Southwest Iowa

Aaron Saeugling (Region 10): “Crop conditions in SW Iowa vary from excellent to below average, all in the same 10-mile drive sometimes. Corn ranges from V5 -V8. Corn spraying has been fast and furious and wind conditions have better than in previous years. Weed control in corn has been variable, with some areas below normal rainfall causing pre-emerge weed escapes. Some carry over symptoms and anhydrous burn along with dry conditions in heavy residue have made for poor corn stands and variable plant height. Soybeans are also finding a few challenges related to stand establishment, mostly due to heavy residue and lack of good seed to soil contact. Herbicide applications on soybean are just now starting and expected to last for the remainder of the month of June. Few insect issues reported as of right now. I expect to see a few pest issues as warmer weather is here, and dry conditions persist into June. Hay conditions were good for first crop alfalfa mostly due to warm weather and low humidity. Regrowth has been slow due to lack of rainfall in most areas. This is setting up to be the have and have nots for rainfall. Some nice rains have occurred in parts of SW Iowa; however, the driest areas struggle to get much measurable precipitation. Looking at stream and river levels is quite concerning for the remainder of the summer. Pastures are green for now and are holding on for most locations.”

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “Rainfall has been hit and miss the last two weeks. While some areas in my area received 2 or more inches, other areas have received a tenth or less. All the counties I cover are classified as abnormally dry on the US Drought Monitor and parts of Marion, Mahaska, Keokuk, and Washington counties are classified as a D1 or moderate drought. Corn ranges from V3-V7, and soybeans V1-V3. A lot of the issues, including fertilizer burn on corn roots (mainly from anhydrous ammonia) and nutrient deficiencies (sulfur and potassium), I’ve seen in fields relate back to the drier conditions. Pasture and hayfields are starting to slow down and regrowth on harvested hay fields has been slower. Main field activities over the last two weeks included post emergence spraying, sidedressing, and harvesting first cutting hay. Questions and field calls have the last two weeks have mainly involved weed identification, weed management and herbicide considerations, fertilizer burn on corn roots, and nutrient deficiencies in corn.”

Virgil Schmitt (Region 9): “Rainfall in the last four weeks in the counties I cover has been generally less than one inch with Muscatine, and Scott counties receiving less than 0.5 inch. In those areas it has been very hit-and-miss. At the weather station near my farm, 0.15 inch of rain has fallen in the last four weeks, scattered over three rainfall events. Shallow-rooted grasses, such a bluegrass is going dormant in many places. First cutting hay is about 85% complete. Farmers are reporting that recovery is slower than normal. I am not sure if that is due to lack of moisture, excess heat, or a combination of the two. Most corn is V5-V6 and looks good to excellent except in areas of coarse soils, clay soils, and compacted areas. Anhydrous injury to root systems is common in some areas. Postemergence spraying is in full tilt. Most soybeans are V1 – V2 and look good to excellent except for areas of coarse soils, clay soils, and compacted areas and areas where crusting issues have lowered populations. Cereal rye is headed out, wild parsnip and poison hemlock are blooming, and musk thistles are bolting. Phone calls, emails, and field visits last two weeks mostly involved soybean replant decisions, weed management and herbicides, and herbicide drift, and nitrogen burn to corn roots.”

Clarabell Probasco (Region 11): “Similar to much of the state, the south-central region of Iowa is receiving pop-up rain showers that are bringing anywhere from a sprinkle to an inch of rain with them. These systems have been very small and very sporadic. Unfortunately, much of the region is in need of a few good rain showers, with portions of Davis and Van Buren County entering the D2 drought zone. Corn fields are around the V6/V7 growth stage and many soybean fields can be found around V2. Both crops are showing stress for moisture but in certain areas that may have had a bit more moisture to begin the growing season with or have been lucky to receive a spotty shower or two, corn fields are getting close to row closure. Herbicide applications have been taking place steadily and some are beginning to wrap up. Much of the first season hay crop has been mowed and is steadily being baled. Many of the hay and alfalfa fields that were cut are also quick to show signs of moisture stress.”

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