Corn Yields Crippled In Southeast Iowa

Crop outlook doesn't look promising in a large area of southeast Iowa, which has been gripped by extremely hot, dry conditions this summer. Lack of rain has diminished corn crop prospects.

Published on: Sep 6, 2011

Southeast Iowa was very wet early in the 2011 crop season and then got very dry during the summer. "That area in recent weeks has been in what is considered a moderate drought," says Jim Fawcett, Iowa State University Extension field agronomist at Iowa City, who covers that area of the state. "We finally got a good shower there on August 31. That was the first rain a lot of areas in southeast Iowa have had since the end of June. Some areas, since the end of June, hadn't had more than an inch of rain until August 31."

"It came a little late for a lot of the corn," says Fawcett. "A lot of the corn is already done in the driest areas of southeast Iowa. This rain on the last day of August may have helped the beans some. But I think a little farther north the rain did a lot more good, particularly for the beans. Some areas in eastern Iowa got a good shower a week before that, which really helped their soybeans."

Yield checks show corn running anywhere from 100 to 200 bu. per acre

So, there's pretty good yield potential in some areas of southeast and east central Iowa on soybeans. On corn, there is some tipping back of kernels on the ears, which means the kernels aren't all the way filled out on the ear tips. The extreme heat this summer was just too much during pollination time.

There will likely be a lot of yield variation even within the same fields, with bottom ground doing well and side hills doing poor, he says. "Yield estimates I've done range from 100 bu/A to 200 bu/A plus. Corn aphids are common in fields now, but are mainly around the ear and hopefully appeared late enough in the season to minimize their impact on the yield."

Farmers will have to pay more attention when choosing corn hybrids

Goss's wilt is showing up this year for the first time in many fields in southeast and east central Iowa. "It's not in every field, but this corn leaf disease is in fields that are planted to susceptible hybrids," says Fawcett. "There are a number of fields where you are seeing the upper leaves die first. Goss's wilt can be very visible when you dry by on the road. A number of fields now have patches in them where the corn plants have been totally dead for awhile from this disease."

Goss's wilt is a disease Iowa farmers will have to pay more attention to in the future, when selecting corn hybrids to plant. If you had Goss's wilt this year, you need to select a resistant corn variety to plant next spring, says Fawcett. There is a lot of difference between corn hybrids and their tolerance to this disease.

What's going on with corn rootworm resistance to CRW corn hybrids?

There have been some problems, mainly in northeast Iowa, with rootworms developing resistance to Bt corn that has the trait for corn rootworm resistance. In other words, some corn with the rootworm resistance trait didn't control rootworm this year.

"It's not a widespread problem as far as we know yet, but I think it's something we are going to see more and more of in the future," says Fawcett. "Some of the Bt corn isn't controlling the rootworms. There are some rootworm populations out there that are already resistant. So we're seeing a lot of root pruning and corn falling down in fields here and there. "It's not a widespread problem," he adds, "But particularly where farmers have planted continuous corn in the same fields for a number of years, and now they've been using the Bt corn rootworm trait hybrids for a number of years, we are seeing some problems with failure to control corn rootworm. We are going to have to deal with that."

What can you do to control rootworm in cases of Bt trait failure?

What Fawcett thinks will be done is that different corn hybrid rootworm trait genetics will be used in the future. The SmartStax trait, for example, where the seed companies are stacking different genes in the same corn plant, will help in this regard. "But it's discouraging that we already have one of the corn hybrid genetic trait events that isn't working well in some fields," he adds.

The ISU Crawfordsville Research Farm field day will be held September 8 in southeast Iowa. ISU Extension climatologist Elwynn Taylor will be one of the speakers. "We have a drought going on in southeast Iowa so we asked Elwynn to come talk about the weather, particularly how he thinks it will affect our yields and corn in general this fall," says Fawcett. "There is a pretty good size area that has been in a drought in southeast Iowa. And the whole state had that heat to deal with in July and early August. That's going to hurt this year's corn yields."

Another speaker at the ISU field day will be Kendall Lamkey, head of the ISU Agronomy Department in Ames. He will discuss advances in corn breeding, in particular for drought-tolerant corn. That will be interesting because the ISU research farm at Crawfordsville actually has some of Pioneer's new Aquamax planted there this year. That's Pioneer's new drought tolerant corn, and "we can see how it did this year because we have had an very dry year at the ISU Crawfordsville research farm in southeast Iowa," says Fawcett.

The Thursday September 8 field day starts at 1:30 p.m. and the event is free with a lot of topics of interest to farmers and the public is welcome.