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Serving: IA

Iowa Has 93% of Corn Acres Planted By May 20

Farmers in southern Iowa warned to watch for black cutworm damage threat on corn.

The weekly crop survey results issued by Iowa Ag Statistics Service on May 21 shows that Iowa had 93% of its corn planted as of Sunday May 20, 2007. A busy and productive week in the fields has brought plantings back to a pace that is near-normal. Corn planting is 5 days behind last year but only one day behind the five-year average, according to the weekly government survey.

Also significant is the fact that 65% of the 2007 corn crop in Iowa has emerged--compared to last year's 67% at this time. The five-year average is 62%. Corn's condition across the state rates 1% very poor, 2% poor, 18% fair, 62% good and 17% excellent, according to the survey as of May 20.

Roger Elmore, Iowa State University Extension corn specialist, notes that the weather has cooperated with farmers quite well the past couple weeks, after those initial heavy rains earlier this spring delayed planting. Hopefully, this "catching up" on planting indicates a good corn crop for 2007.

Iowa has four corn crops this spring

Over 61% of the state's soybeans are now planted and 12% were emerged as of May 20. Soybean planting is equal to the 5-year average while emergence is 2 days behind average, the survey shows.

Iowa State University crop specialists from around the state held their weekly telephone conference on May 21. They had the following comments.

Iowa farmers made great strides over the last 10 days in getting the corn crop planted. In a lot of areas of the state this week, farmers are now going back and planting some of the wet spots in fields that are finally drying up enough to allow corn planting. "With regard to soybean planting this spring, it isn't as far along as some farmers would have liked, but in certain areas of the state farmers are now done or soon will be with beans too," notes ISU's Mike Owen.

With the rains Iowa had earlier this spring that slowed down planting, Iowa essentially has three or four different corn crops out there now.

* First there's the early planted corn – which looks really good.
* Second, there's the corn that was planted between rain showers. That corn is coming up ok. The stands are okay, but the plants are looking a little yellow.
* Third, there are cases where farmers rushed planting into wet soils and now they have corn root development problems showing up. The ground was wet when the corn was planted and it didn't get proper closure of the seed furrow.

Potential for black cutworm damage

Brad Van Kooten is an area agronomist for Pioneer for the southern third of Iowa. "We are finding early indications of black cutworm damage on some corn fields," he said on May 21. "The first signs are when you see pinhole feeding on the leaves. I've seen that throughout southern Iowa the past few days. We've also had reports of a few fields that have already been treated for black cutworm in Lee County, Iowa. Fields have also been treated farther south in Illinois."

Black cutworms like to attack corn early, when it is in the V1 to V2 stage, fairly early-on, when the corn is small. When the corn gets to about five leaf collars then the corn is large enough that the black cutworms don't have the ability to cut off very many plants and the pest tends to be less of a threat, says Van Kooten.

What's his recommendation for economic threshold of when to treat and which insecticides to use? "We recommend farmers keep an especially close eye on their refuge acres of corn," he says. "Bt refuge acres are especially vulnerable to cutworm attack. Also, fields that do not have Herculex protection are more vulnerable to black cutworm damage. Other types of Bt don't offer cutworm protection, but corn hybrids with the Herculex trait do have good protection."

"If you find 2% to 3% of the corn plants are being cut off and the black cutworms in the field are three-quarters of an inch or less in length, we suggest treatment with a rescue spray of insecticide," he says. "If the black cutworms are a little larger, say one inch in length, then 5% cut plants is the threshold to follow. In this case if the cutworm damage reaches 5% of the plants being cut off, then you should spray. That's according to Iowa State University entomologists."

TAGS: Extension
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