Regional Crop Update: May 25 - June 2, 2020

June 2, 2020 3:57 PM
Blog Post

The crops have really started to take off this past week with the warmer temperatures. While rainfall limited field activity in parts of the state, where fieldwork could be done many got started on sidedressing, post herbicide applications, and putting up hay. Yellow and uneven corn, weed pressure and insect pests including thistle caterpillars, cutworms, alfalfa weevils, and aphids in alfalfa seemed to be some of the more common issues ISU Extension field agronomists saw and heard about this past week. Read on for more information about what’s happening in specific regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “In the NW corner of the state, this past week was rather dry. The temperature is finally turning around, and growth is really beginning for corn and beans. Almost all the soybeans are emerged, with very few acres left to plant. This looks to be the “ugly duckling” week for corn – where any small difference in the plants will cause uneven looking and uneven colored corn. However, there seems to be adequate soil moisture in the root zone and the warmer temperatures should get us through this stage quite rapidly. Post herbicide applications on corn began last week and will continue this week when the wind isn’t too high. It is needed, because you can see the weed pressure really taking off. Alfalfa cutting started late last week, with few reports of alfalfa weevils here. However, the aphid numbers seem quite high.”

Paul Kassel (Region 2): “The corn crop is developing rapidly. Areas with poor soil drainage are obvious since many of them have taken on a purple/brown color.  Corn development has gone from the V3 stage to the V5 stage in about five days in many fields. There has been a lot of postemergence herbicide applications mades to the corn crop late last week and this week, which is needed as there is a lot of waterhemp and other weeds coming to life. There are fields that are gaining a pink/purple color where the waterhemp seedlings are breaking through the corn pre-emergence herbicide program.” 

April planted corn in Kossuth County in the V4 stage. Photo courtesy of Paul Kassel.

April planted soybeans in the V1 stage. Photo courtesy of Paul Kassel.

 North Central Iowa

Angie Rieck-Hinz (Region 3): “For the week of May 24 through June 1 we saw varying rainfall amounts across NC Iowa, from 1.37 inches at Humboldt to 3.5 inches at Mason City.  From May 22 through May 28, I received 5.5 inches at my house in northern Story County, and it is reflected by the amount of water ponded in fields. Calhoun, Webster, Hamilton and Hardin county are no longer listed as D0 (abnormally dry) on the drought monitor, but as of May 28, Wright, Franklin, Cerro Gordo and Worth still show up as abnormally dry. Again, I anticipate that to change this week with the recent rains. Corn across NC Iowa is V2 to V4 and soybeans are V1 to V3.  Generally speaking, the corn is finally moving out of that “ugly” yellow color. There may be some replanting of ponds depending on how quickly they dry up. We will hit postemergence herbicide applications hard as fields are starting to look weedy. I had multiple phone calls about alfalfa weevils last week. I also looked at some soybean fields that had been rolled when it was too wet, causing the surface to crust and soybeans to die and/or break off when trying to emerge.”

Soil crusting in this field that had been rolled when it was too wet caused some soybeans to break-off and die when they tried to emerge. Photo courtesy of Angie Rieck-Hinz.

 West Central

Mike Witt (Region 6): “The heat and the moisture arrived last week. West Central Iowa received anywhere from half an inch to two plus inches of rain over the last week. However, there are some areas that are lacking moisture and are listed in the U.S drought monitor at the D0 or Abnormally Dry classification. With the lack of significant rain in the forecast these areas for the next week should monitor the situations. Corn across the area is at the V2 to the V4 growth stages and will be growing fast. We should be gathering heat units at a good rate with the temperatures this week, so corn should start to emerge from the yellowing stages and into the darker green we are accustomed to seeing. Soybeans are in the VE to V2 stages and will also benefit from the warmer temperatures. Weed pressures around the area are becoming more evident as pre-emergence herbicide performance or herbicide decisions are starting to become visual in fields. Post emergence spray season is here for some farmers and will pick up in intensity over the next few weeks. On the insect front there are reports of the thistle caterpillars making appearances across the area. This pest did cause some significant damage to soybean fields in WC Iowa last year; however, it doesn’t overwinter here so it will be important to scout fields to determine if any action is warranted. Alfalfa fields are nearing the budding stage if not there already, and the first cutting is commencing around the region.”

US Drought Monitor showing parts of WC and NC Iowa as being abnormally dry. Source:

Northeast Iowa

Terry Basol (Region 4): “The weather the last couple of weeks has helped restore our topsoil moisture, but the cooler conditions have slowed crop growth. Some of the corn does look pale yellow and some also a little purple, but the corn should grow out of this with the warmer weather and sunshine this week. Most of the corn in NE Iowa ranges from V1 to V3. While, we are currently a little behind on Growing Degree Days (GDD’s), the forecast for the next few weeks looks promising to get caught back up. Growers have started in on postemergence herbicide applications and sidedressing nitrogen. Now is the time to also be scouting for black cutworm activity and feeding in corn. Soybean range from VE to V1, and according to the June 1 USDA Crops Progress Report, soybeans in NC Iowa are 96% emerged and 84% emerged in NE Iowa. Overall, soybeans look good. Looking forward to a week of sun and warmth, giving growers a chance to work on timely field operations for the corn, soybean, and hay crops in the area.”

Central Iowa

Meaghan Anderson (Region 7): “Crops are starting to take off with the warmer weather and sun, but we are starting to notice more unevenness and issues across fields. Around the V3 stage for corn, nodal roots take over, and corn that is struggling will continue to look yellow or show other symptoms of belowground problems, while corn with better root systems takes on the pretty, dark green color we like to see. I’ve seen herbicide carryover, uneven planting depth, grub activity, and anhydrous ammonia burn in corn fields in the past week. Postemergence herbicide applications in corn started over the weekend but have hopefully stalled during the windy afternoons this week. We’ve had countless reports of significant grass and velvetleaf infestations that broke through PRE applications in corn fields. The earliest waterhemp escapes are 3-4” tall already but most are <1” tall still. Soybeans are anywhere from just emerged to V1 (maybe V2 in some fields) and really look relatively fantastic. Most soybean fields are clean, stands are fairly even, and I’ve seen little insect activity so far. I spotted my first thistle caterpillar larvae on June 1, but populations seem very low in central Iowa. I’d encourage field monitoring but would discourage against widespread use of insecticides if fields are not at threshold levels for defoliation. Postemergence herbicide applications for soybeans will likely be happening later this week, and farmers using dicamba will want to be especially careful with applications given the application restrictions for these products.”

Thistle caterpillars have been spotted in Central Iowa but so far at low levels. Photo courtesy of Meaghan Anderson.

Corn plant showing PPO herbicide carryover injury. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “This past week brought some warmer temperatures and anywhere from about half an inch to 1.5 inches of rain across EC Iowa. Crops have really taken off in the last week. Most corn fields seem to range from V3 to V5 and soybeans are mainly VC to V1. Sidedressing, postemergence herbicide applications, and taking the first cutting of hay were the primary field activities this past week. Insects and weeds seem to be the big pest issues so far this year. Insects I’ve either seen or have heard about include black cutworms, bean leaf beetles, alfalfa weevils, and pea aphids in alfalfa. While the weeds are also taking off with the warmer weather, pay close attention to weather conditions when spraying.”

A good reminder to pay attention to conditions when spraying. This red clover-alfalfa-orchardgrass hayfield was drifted on with mesotrione, which red clover is especially sensitive too. Photo courtesy of Rebecca Vittetoe. 

Virgil Schmitt (Region 9): “In general, rainfall last week in the counties I cover was half an inch to 1.5 inches. Temperatures last week in the counties I cover were one to three degrees warmer than normal. A great deal of hay was cut over this past weekend. Most corn fields are at V3 to V5 and look good. Soybeans are mostly VC to V1. In general, they also look good. Smooth bromegrass and orchard grass are headed out, and most clovers are blooming. Wild parsnip is also blooming. “June bugs” are numerous. Herbicides, herbicide drift, nitrogen applications, rye cover crop termination by harvesting, and grain bin management dominated calls last week.”




Josh Michel (Region 11): “Most of my region received one to two inches of rainfall over the past week, with a few isolated areas receiving up to three inches. For many, the first cutting of alfalfa has been harvested. Pastures have continued to look good and be productive thanks to the rain and slightly cooler temperatures. Corn is generally at V2 to V3, with some early planted corn at V4. Although there have been some reports of uneven stands, most of the corn is looking good. Soybeans are generally at V1 to V2, with some early planted soybeans at V3. Besides a few small areas, any replanting of corn and soybeans has been completed. Field calls last week mainly consisted of weed management, herbicide applications, nitrogen sidedressing, replanting, thistle caterpillars, bean leaf beetles and alfalfa weevils.”

Keep an eye out for bean leaf beetles in soybeans. Photo courtesy of Josh Michel.

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...