Frost injury, replanting and seedling diseases reported across Iowa

Frost injury, replanting and seedling diseases reported across Iowa

ISU agronomists say some farmers are replanting corn and beans due to soil crusting.

A lot of soybean planting progress was made across the state this past week, as farmers tried to get ahead of this week's daily rain forecast. Most corn planting has been completed in Iowa, with 75% already emerged, according to the May 23 USDA weekly Crop Progress Report. Replanting is likely in some areas of northwest, southwest and west-central regions from the excessive wet conditions this spring.

HOW IS YOUR STAND?: Take a good look at your corn and soybean stands as they emerge. “We’ve had a number of questions on emergence issues and herbicide injury lowering stands,” says Aaron Saeugling, ISU Extension field agronomist in southwest Iowa.

Central and north-central Iowa saw some frost injury across the regions last week, as a result of last weekend's low temperatures. Seedling diseases have been reported in southeast and east-central Iowa over the past week, along with planter adjustment issues. Read more about your region from Iowa State University Extension and Outreach field agronomists, as they provide the following report on planting progress and field conditions.


Joel DeJong (Region 1): "We had several good planting days this past week and probably have all the corn in the ground that will be planted. Corn acres left are acres that we haven’t gotten dry enough to get to. We also had a lot of rotary hoe use to try and soften the crust on acres planted May 6, 7 and 8 that were having emergence problems after a heavy rainstorm not long after it was planted. Replanting from crusting, and standing water, and stand losses—probably the most we have seen here for many years. Soybean planting progress last week was great. Many in the area are now done, and we are approximately 80% complete as a whole. However, it rained again this morning, May 23, so we are on hold again."

Paul Kassel (Region 2): "My eastern area has completed corn and soybean planting; many of the farmers completed corn and soybean planting about two weeks ago. The western part of my area just completed corn planting and is about 75% complete on soybean planting. There is a fair amount of replanting across my entire area. Some of the replanting is due to excessive rainfall and standing water. And some of the replanting is due to poor stands from poor drainage/wet conditions at the time of planting. However, a lot of the April 15-17 planted corn looks really good."


Angie Rieck-Hinz (Region 3): "In north-central Iowa, we have been done planting corn for nearly two to three weeks and soybeans were wrapped up last week. We had some frost damage from low temperatures the morning of Sunday, May 15. Some corn lost all leaves above the soil line, but growing points were not damaged and the corn is recovering from nearly all reports I have received. Corn is in the V2-V3 growth stage and soybeans are VE to V1. Alfalfa cutting has started. I have seen some scattered cutting of corn from black cutworms, but nothing near the threshold needed to justify treatment with an insecticide. We could actually use some rain to help with bean emergence in some crusted soils."


Brian Lang (Region 5): "On May 18, I had two reports of high populations of Pea aphids in alfalfa; one from Angie Rieck-Hinz, ISU Extension agronomist in north-central Iowa, and one from Nikki Schulte, Pioneer seed dealer/agronomist near Dorchester. That’s quite a wide swath, although I had not seen any around Nashua or Decorah in the last two days. It takes a lot of aphids to reach threshold, and populations can be spotty across fields. Here are the four most common aphids found in alfalfa fields and economic threshold guidelines from publication IPM-58: The Four Most Common Aphids Found in Alfalfa Fields(1).pdf.

As with most insect thresholds and forages, if it is less than a week to harvest, take the harvest (move it up a bit if possible). If it is more than a week from harvest, consider a treatment. The harvest process kills many aphids, but not all. Whether the population rebounds is anyone’s guess. Weather will change; maybe still favorable for the insect, maybe not. Beneficial insects get a start on a lower population of aphids after harvest. However, typical management for second crop growth is to treat for Potato leafhopper at just a few inches of alfalfa growth, which would also handle any aphid rebound."

Southwest and West-Central

Aaron Saeugling (Region 6): In southwest Iowa, we currently have over 95% of the corn planted with some emergence issues due to wet soil conditions. I have heard of some isolated black cutworms and damping off of corn seedlings. Soybean planting is around 60% to 80% complete; a wide range of variability in this area. Some emergence issues as a result of cool soil temperatures, excessive moisture and crusting. Rye is currently being harvested for silage and a few fields of hay have been mowed. Most producers are waiting until the current wet weather has moved out to mow forages.

Clarke McGrath: "In southwest/west-central Iowa, most of our soybean plots are in, so that typically signals that soybean planting, in general, is wrapping up. Corn planting is complete, but heavy rains and crusting issues are setting us up for replant situations. There was some corn replanted Saturday and Sunday (May 21 and 22), and it will continue today (May 23) until the rain starts. In some cases, the rainfall will likely help enough seedlings come through that the fields slated for replant will actually end up being left because by the time we can get back in:

1) The rain may have softened the soil and allowed a few more plants to emerge, or

2) It will be late enough that the stand out there might have to be “good enough” by the time it is dry enough to get back into the field.

In addition to the replant, there have been pockets of corn needing the rotary hoe or the harrow drug over it to help break up the crust. I’ve had comments and questions on that from Little Sioux to Walnut, a pretty long run. A rough and wild guess is that 20,000 to 30,000 acres have been impacted.

I’d urge growers to take a good look at their soybean stands as they emerge. I’ve had a fair number of questions on emergence issues and herbicide injury lowering stands. For the most part, it doesn’t look like it will necessitate much replant, but there are a few overlap areas or wet areas where growers say they will either completely start over or spike in another 50,000 to 70,000 of beans when they get a chance. Watch for a lot of spraying and urea spreading once the weather clears and we can get back in the field; there will be a massive amount of sprayers and tender trucks on the road. Drive safe!"


Mark Johnson (Region 7): "My area is 99% done with corn and very near 99% done with soybean planting. I’ve had no calls on seedling disease in corn or soybeans. I had one call in northern Marshall County on soybean frost damage, but it was spotty in the field and made making a decision difficult. That farmer will probably try to plant 70,000 seeds per acre in small patches without tearing the original stand up and leave the rest alone. He was in 15-inch rows, and would add to those areas by planting in a different direction.

I’ve had one call in southern Marshall County on corn frost damage and while the aboveground portion on many of the corn plants looked bad, the growing point was fine and no replant was needed. I did see one farmer baling hay yesterday in Story County."

Southeast, South-Central, and East-Central

Rebecca Vittetoe (Region 8): "In southeast and south-central Iowa, planting progress for corn has basically wrapped up, but soybean planting progress varies more in my area (south-central Iowa) yet. The farthest along I’ve seen corn in my area is at V2 growth stage, pushing V3 and VC, pushing V1 for soybeans. There has been some scattered reports of black cutworm damage to corn plants and corn seedling diseases in my area. There was a lot of first cutting alfalfa being mowed at the end of last week."

Meaghan Anderson (Region 9): "East-central Iowa is almost complete with both corn and soybean planting. I still see a few fields not planted here and there. We have lots of corn in that V2 to V3 range and a lot just emerging, as well. Soybeans are anywhere from just planted to VC growth stage. There have been scattered reports of minor black cutworm feeding on corn and bean leaf beetle showing up, but nothing economic. I’ve heard many reports of seedling disease in the Washington County area, accompanied with planter issues; get out and scout your fields!"

Virgil Schmitt (Region 10): "Fieldwork resumed in earnest on Tuesday (May 17) with corn and soybean planting and mowing hay. By the end of the weekend (May 22), corn planting was virtually complete, soybeans were about 90% planted, and hay cut earlier in the week had been baled.

There are some fields where crusting has posed and is posing a challenge for corn and soybean emergence, and rotary hoeing was observed starting on Thursday, May 19. Corn is mostly in the V2 growth stage or more, and soybeans are mostly not emerged to VC growth stage—as of May 23.

There are a few cornfields in which seedling diseases and/or planter adjustment have resulted in stands that are low enough to justify replanting. There have been reports that crop insurance adjusters are receiving lower-than-expected soybean stands. There were a few fields planted just before the cold, wet weather that occurred about two weeks ago. However, the cause is not yet known."

Find your local ISU Extension and Outreach field agronomist here!


TAGS: USDA Extension
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