Iowa Corn, Soybeans Continue to Look Good

Soybean aphids are now under control; rain this past week has also helped improve crop yield prospects.

Iowa's corn and soybean crops continue to look good, despite lingering effects of drought in the northwest part of the state and extreme heat over the entire state the past seven days. Soybeans statewide are now well into pod fill, at growth stage R4 or more. The state's corn crop is maturing rapidly too.

Rains have helped, although there are still some dry pockets in the state that could use more moisture. Here's an update on the soybean aphid situation as of August 14--from the Iowa Soybean Association's statewide scouting network.

"After a couple weeks of hectic insecticide application, it appears the insecticides and weather have combined to thwart the spread of soybean aphid," says Mick Lane, research communications manager for ISA. "Our observation is based on this week's summary of reports coming into our office from the crop consultants working with us in ISA's Scouting Network this summer across the state of Iowa."

Half of Iowa bean acres have been treated

During the past two to three weeks, about half of Iowa's soybean acres have been treated with insecticide for control of soybean aphid. "The control has been good," says Lane. "Some crop consultants watching fields where aphid populations were approaching economic threshold this past week now say aphid numbers have since leveled off--or have even declined in some cases."

That is likely due to the weather. If the weather is favorable, aphid populations can explode within a few days. On the other hand, if weather is unfavorable, aphid numbers won't increase and in fact, may even go on the decline.

Bean leaf beetles are another summer insect that's surfaced in many bean fields this summer. Bean leaf beetle reached economic threshold in a few fields in Iowa this past week--in fields where aphids were still below the threshold for treatment. And some fields where aphids had been previously controlled with an insecticide application may have a second generation of aphids now developing.

What about bean diseases last week?

"When scouting fields in Iowa this past week or so, crop specialists are seeing some Downy Mildew, and some frogeye leaf spot and some sudden death syndrome or SDS," says Palle Pedersen, Iowa State University Extension soybean agronomist. "Those diseases are particularly prevalent in southeast Iowa, but they aren't limited to that area. White mold is another disease that is present in some fields right now."

What lessons are you seeing on corn?

While there are a few persistent—but not acute—disease and insect problems in cornfields in 2007, crop consultants say the 2007 Iowa corn crop seems to be well on it's way to producing the 150-plus bushels per acre yield average USDA is predicting in it's August 10 Crop Production Report. The only exception is in northwest Iowa, where early drought this summer has taken its toll.

"One crop consultant told us last week about the fields he scouted in northwest Iowa. One field sill benefited greatly from more rain in August. But the other field may not," notes Lane.

Corn growers seeing disease problems

Most of the cornfields in the ISA's weekly crop scouting program for 2007 have reached dough state (R4) already, or they are now going into early dent (R5 to R6), with only a few fields still at milk stage (R3).

Specific corn diseases of most concern to growers this August are gray leaf spot and common rust. Stewart's wilt, anthracnose and eyespot are also being noted in some fields in Iowa this summer. In addition, northern and western rootworm beetles are showing up in what the farmers describe as "thin soils."

The ISA On-Farm Network will soon begin shooting aerial photos off all corn fields in this program. The imagery will be used to determine where to collect corn stalk samples from every cornfield that is participating in this statewide program. "We want to use these pre-harvest nitrate tests of corn stalks," says Lane. "The results will be available early this winter."

August Crop Report indicates a whopper

In its weekly weather and crop conditions report issued August 13, Iowa Agricultural Statistics Service says 87% of the corn plants in Iowa are now in the milk stage. That 87% is equal to last year, but 6% ahead of the 5-year average.

Corn in dough stage is at 52% of the Iowa acreage, is now equal to last year, but 9% ahead of the 5-year average. Corn in dent stage is now at 14% or 1% ahead of last year and 6% ahead of the 5-year average. Corn condition statewide in Iowa is rated at 2% very poor, 8% poor, 26% fair, 46% good and 18% excellent, as of the Crop Report issued August 13.

Over 89% of the soybeans in Iowa are currently setting pods, and 2% are behind last year in maturity. However, this is still 1% ahead of the 5-year average.

Soybean condition is rated at 1% very poor, 4% poor, 24% fair, 52% good and 19% excellent. The second cutting of alfalfa is virtually complete. The third cutting of alfalfa is 34% complete, well behind last year's 46% and 4% behind the 5-year average. All hay condition is currently rated 6% very poor, 20% poor, 31% fair, 38% good and 5% excellent, based on the statewide surveys.

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