Iowa Field Reports: Concerns of Frost Damage, Uneven Crop Emergence

    Thin soybean stand. Photo: Mike Staton, Michigan State University

    Planting is starting to wrap up around the state for both corn and soybeans, and according to the May 17 NASS-USDA Crop Progress Report, 94% of the corn has been planted and 83% of the soybeans have been planted. Concerns Iowa State University Extension and Outreach field agronomists heard and saw about this past week included some frost injury in the northern part of the state, uneven crop emergence, and alfalfa weevil larvae.

    Read on to see what’s happening in specific areas across the state.

    Northwest Iowa

    Joel DeJong (Region 1): “Rain for this region was between about 0.2 to 0.6 for the week. Some cold overnight temperatures did cause some leaf damage in low-lying areas last week, but I have not heard of any replants needed from that. Warmer average daily temperatures did help get a lot of corn out of the ground, and a high percentage is now emerged.

    “Soybeans have started to emerge, maybe 20% are up as I write this on Monday, May 17. Some appeared to be in dry soil earlier, but the fields I checked recently all seemed to have had enough moisture to get these seeds going. However, we will likely know more as additional fields emerge.

    “Pastures still appear slow to grow, and alfalfa is nearly 20” tall and still in the vegetative stage in the fields I have been watching. Today was the first day I noted some leaf feeding from alfalfa weevils.”

    Paul Kassel (Region 2): “Many farm operations are currently caught up on field work. Most farmers are checking emergence and evaluating plant populations. Emergence of both corn and soybean crops has been slow this spring. There has been some replanting of corn. Farmers and agronomists are using a plant population of around 25,000 plants per acre as a minimum before they consider replanting corn.

    “The next activity will be postemergence herbicide application to corn.  Like crop emergence, weed emergence has been slow also. Most farmers and applicators are waiting on warmer weather and additional weed emergence before making postemergence herbicide applications.”

    North Central Iowa

    Angie Rieck-Hinz (Region 3): “We experienced two mornings of frost the week of May 10, with reported temperatures dipping to 29 degrees in some places. It was not hard to find water-soaked looking or dead tissue on corn leaves that had emerged. I did not see any frost damage on soybeans, but most beans I looked at late last week had just emerged.

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    “It is not inconceivable to believe that some of the earlier planted soybeans were impacted by those temperatures. Phone calls continued with concerns about uneven emergence in corn. Rains continued to be highly variable for the week of May 9-16, with Rockwell City receiving 2.37 inches and Northwood 0.02 inches.

    “A scouting advisory for Black Cutworms has been issued for May 19 for the NC Crop Reporting district, with earlier dates for the West Central and Central Iowa reporting districts. I have been scouting a few cover crop fields that have been terminated and now have corn emerging and will continue to do so.

    “Corn is mostly VE to V1, with a very small percent at V2, and soybeans are VE to VC. There are still soybean fields to be planted, my guess is they are seed fields.”

    Northeast Iowa

    Terry Basol (Region 4): “Planting has basically been completed for corn, and soybeans aren’t far behind.  It’s easy to row both corn and soybeans fields from the road now. Most of the corn falls in the VE to V2 growth stage and soybeans in the VE – VC growth stage. Take time to assess stands now. Doing this early helps to detect any agronomic problems that can arise and also allows enough time to make proper decisions.

    “As you are checking stands, also be on the lookout for black cutworm (BCW) activity in corn fields, as the estimated cutting dates are expected around May 19 in NC and NE Iowa. Temperatures dipped down around freezing last week for a very brief period, and there was some frost injury in low lying areas to alfalfa stands.

    “From what I’ve seen, it just affected the leaves a little and didn’t cause any considerable plant mortality. Hoping that this week’s forecast will provide some much needed rain. According to the Iowa Mesonet, the NE IA Research and Demonstration Farm at Nashua has only received 1.6 inches of rain from April 1 to May 17, which is 4 to 4.5 inches below normal rainfall.”

    Josh Michel (Region 5): “While most areas in the northern part of the region received only 0.10 to .25 inches of precipitation, some isolated areas along Highway 20 received up to 1 inch of rainfall. After a few days to dry out, planters could be seen back in the fields as early as Thursday last week, trying to finish up this year’s planting season.

    “Even with planting quickly coming to a close, there has been great concern in regard to recent temperature lows around or below 32 degrees. This has resulted in some isolated fields with frost damage on the tips of corn leaves, soybean cotyledons and even leaf damage in alfalfa. I’d estimate that around 85-90% of corn acres have been planted, with soybeans around 75-80%.

    “The earliest planted corn fields are at V1, while soybeans are still just emerging. Alfalfa is continuing to look great, but growth has been slow due to cooler than normal temperatures. The majority of planted oats have emerged and stands are looking good so far. Pastures continue to also do well with cool temperatures and some timely rain.

    “Recent field calls and questions have included the following: late cover crop termination, weed identification and controlling escapes, pasture management, corn rootworm management, and questions pertaining to frost damage to crops.”

    Central Iowa

    Meaghan Anderson (Region 7): “Central Iowa got some much, much needed rain recently with more predicted on the way. Much of the corn is emerged across the area and ranges from really even and consistent to quite uneven. Most corn is in the VE to V1 stage but there are a few fields ahead of this.

    “Uneven emergence may relate to several issues like variable moisture, variations in soil temperature, residue placement, soil cloddiness, or even seed quality. As crops emerge, now is a great time to get out, take some stand counts, and try to determine what happened in areas with missing plants.

    “Some areas of central Iowa got frost last week, so don’t be surprised if you seed some corn plants with brown leaves or parts of leaves, especially in fields with cover crops or higher amounts of residue. Soybeans that were planted into good moisture in late April and early May have now emerged and look really nice, with many fields at the VE or VC stage.

    “Recent calls have been on uneven corn emergence, frost on corn, herbicide programs, and cover crop termination.”

    East Central, Southeast, and South Central

    Rebecca Vittetoe (Region 8): “Planting is getting close to wrapping up with about 95% of the corn planted and 80 to 85% of the soybeans planted. It’s pretty easy to row a lot of fields now with the furthest along corn I’ve seen being at V2 and soybeans at VC. The big concern I’ve gotten this past week has been on uneven crop emergence, particularly for the crops planted around that April 20 to 25 window.

    “Take time to scout and check your stands. Now is also the time to be scouting for black cutworms. Alfalfa/hayfields and pastures are looking good, just slow on growth this spring. It’s not hard for me to find alfalfa weevil larvae along with some aphids in alfalfa fields this spring.

    “Rainfall totals over the last week in EC Iowa ranged from 0.1 to closer to 2 inches of rain, with the heavier rain falling south of I-80. We could really use some sunshine and heat now.”

    Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was generally 0.1 to 1.5 inches of rain, with the heaviest rains south of I-80. In general, temperatures last week in the counties I cover were 5 to 7 degrees below normal. Corn planting is about 95% complete and soybean planting is about 75% complete.

    “Emerged corn in mostly V1 to V2. The most advanced soybeans I have seen are VC. Hay harvest began late last week and there is light alfalfa weevil damage in most fields. Corn post-emergence herbicide selection and cereal rye hay harvesting were the main topics of conversation last week. I have heard of no serious black cutworm feeding, but farmers should be scouting for black cutworms on all corn until it reaches V5.”

    Josh Michel (Region 11): “Scattered rain showers continued to deliver around 1 to 1.5 inches of precipitation across most of the region, with some isolated areas receiving up to 2 inches. Towards the end of last week, planters could be seen trying to finish planting before the next round of showers arrived last Friday night into Saturday morning.

    “Corn is around 95% planted, and soybeans are 80 to 85% planted. The earliest planted corn fields are around V2 and most soybeans are just emerging. Alfalfa fields continue to look good, but first crop may be shorter than normal in many fields due to cooler than normal temperatures.

    “Oat emergence is around 75 to 80%, and oat stands look good. Pastures also continue to look great with cooler than normal temperatures and recent heavy rainfall. Calls and questions have centered on delayed cover crop termination, weed identification and escape control, as well as pasture, alfalfa and small grains management.”




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