Iowa Corn Is Tasseling, Could Use Rain

Corn is tasseling or rapidly approaching that stage, and soybeans are in full bloom. Eastern Iowa remains dry. Rod Swoboda

Published on: Jul 12, 2005

Overall, Iowa’s corn and soybean crop is in very good shape. But we could use a rain. That’s how Mike Owen, Iowa State University extension weed control specialist, sums up the crop situation in the state, as of July 11.

Each Monday, Owen and other agronomists at ISU hold a telephone conference with the ISU area extension crop specialists scattered around the state.

"As you go from west to east in Iowa right now, it is getting pretty dry," notes Owen. "In the eastern part of the state, in particular in southeast Iowa, we need rain. Corn is beginning to wrap up its leaves in the afternoon heat. We’re also seeing secondary issues of moisture deficits--such as spider mites on some of the fields of soybeans in far southeast Iowa."

Northwest Iowa is 2005 garden spot

"Statewide, looking at Iowa, we’re not in bad shape," he adds. "But the crops do need a rain as you go west of Cedar Rapids and drive into central Iowa. On some of the hilltops, we’re beginning to see some corn leaves curling or wrapping. But in general in central Iowa, crop conditions still look pretty good."

The areas of northwest Iowa and north central Iowa that were thought to be in so much trouble earlier this spring are now the garden spots of the state.

The one thing that is of concern is that most of the state’s corn crop is tasseling now or soon will be--and the temperatures are quite hot and we could use a good rain. The pollination period needs moderate temperatures to make sure we get good pollination of the corn crop, notes Owen.

What this week’s Iowa crop report shows

According to the latest weekly statewide survey by Iowa Ag Statistics Service--which was released July 11--topsoil moisture across Iowa currently rates 12% very short, 27% short, 57% adequate and 4% surplus. Subsoil moisture rates 7% very short, 22% short, 64% adequate and 7% surplus.

Corn condition rates 1% very poor, 4% poor, 19% fair, 52% good and 24% excellent. Average corn height is 63 inches, up 12 inches from a week ago. Corn tasseled reached 19%, up 17 percentage points from a week ago and slightly ahead of the 5-year average of 16%. Corn silked is rated at 7% complete, slightly behind last year's progress of 8% and the 5-year average of 11%.

Statewide as of July 11, Iowa’s soybean acreage blooming reached 48%, slightly ahead of last year and the 5-year average. Soybeans setting pods is at 5%. Soybean condition rates 1% very poor, 4% poor, 20% fair, 56% good, and 19% excellent. The oat acreage turning color is 82% compared to 54% the previous week and 21 percentage points ahead of the 5-year average of 61%.

Oats harvested for grain reached 7%, slightly ahead of last year and the 5-year average. Oat condition rates 5% poor, 23% fair, 56% good and 16% excellent. Second cutting of alfalfa is 63% complete, up 30 points from the previous week. Hay condition is 2% very poor, 6% poor, 27%fair, 55% good and 10% excellent.

Livestock are in good condition and calves are growing well. Pasture and range condition rates 3% very poor, 11% poor, 34% fair, 46% good, and 6% excellent. Lack of rainfall has lowered pasture condition from a week ago.

Soybean aphids are now in many fields

Some areas of the state are beginning to see aphids showing up on soybeans, but nothing like the infestation Iowa had in 2002. "Farmers and agronomists are beginning to find a few aphids in soybean fields," says John Holmes, ISU area crop specialist at Clarion, Iowa. "It’s prudent to be scouting for them now."

Marlin Rice, ISU extension entomologist, is finding an average of 40 aphids per plant in plots on an ISU research farm south of Ames. He also found individual plants outside the scouted area that had considerably higher aphid populations. Remember--Hot weather drastically reduces aphid reproduction.

In north central Iowa, Holmes says he’s received reports from farmers and crop scouts of heavy feeding from corn rootworm on corn following soybeans due to extended diapause of the rootworm. He’s also getting reports that western bean cutworm moths were being captured in increasing numbers during the past week.

Holmes says nearly all soybean fields in his area have bacterial blight and are showing some brown spot disease this summer. "I’ve also seen or looked at a lot of fields injured by herbicide drive this season," he says.

Tank mix insecticide, fungicide, herbicide?

Some agronomists and farmers are considering "throwing in" an insecticide with the second glyphosate application or with a fungicide application. "Two thoughts come to mind," says Holmes.

First, coverage requirements, and hence the nozzles required, are different for herbicides vs. fungicides or insecticides. Second, an insecticide will kill beneficial insects and may favor development of other pests such as spider mites.

"It’s always wise to follow integrated pest management principles when treating for crop pests," says Holmes.

Western bean cutworm moths are flying

Rich Pope, ISU extension associate, is coordinating the western bean cutworm trapping program across Iowa this summer. He reports that western bean cutworm capture numbers are increasing now. Click on www.ent.iastate.edu/trap/westernbeancutworm for the most current information.

You may find a few egg masses being laid on the corn plants. Read up on "how to scout" for this pest and what to look for, regarding degree days and when to begin potential treatments. "The bottom line is, watch the corn," says Clarke McGrath, ISU area crop specialist in southwest Iowa. "If we hit the threshold, spray as quickly as possible. That’s easier said than done, I know."

What’s going on with soybean rust? This new disease hasn’t moved into the Midwest yet. So far, it’s still only shown up in the South. As of this week, it has only made its way as far north as Alabama. But keep an eye on your bean fields.

When could soybean rust first start showing up here in Iowa--during the summer of 2005? "Hurricane Dennis could make things a little more dicey," answers McGrath. "But every day this summer that rust doesn’t progress towards us here in Iowa, that gives us a little more reason for cautious optimism that we may dodge the bullet this year. Hopefully it will just say down there in the south."