Heavy rains and wind have caused a lot of lodging in various locations in Iowa the past two weeks. But high corn and soybean yields are still likely for Iowa this year. That's the conclusion of the weekly crop scouting summary, released by the Iowa Soybean Association Crop Scouting Network on August 30.
Late season disease and insects are present. But crop consultants working with the ISA scouting network say weather was the biggest factor affecting Iowa's corn and soybeans last week. Rainfall amount for the previous week in many of the fields was more than 4 in., and in one location, the report was more than 10 inches of rain.
"Soggy soils and winds have laid both corn and beans down on the ground in many of the fields being scouted this past two weeks. And disease spread has been encouraged by the warm, damp weather," says Mick Lane, research communications manager for ISA.
Soybean diseases are showing up
In soybeans, a couple of fields have matured to the R7 growth stage, but most are at R6. Soybean aphids are still present in many fields, but they're at or approaching threshold in only one or two. Diseases present include frogeye leaf spot, downy mildew, brown spot, bacterial blight, sudden death syndrome. White mold is beginning to show up, particularly in some of the lodged, tangled beans.
In corn, maturity is at R5 or R6 for all fields being scouted in the network, except for one in Clayton County that was planted on May 10, which is still at R4.
Crop consultants say that despite insects and the combination of wet soils, winds and late season disease, the corn crop is still looking very good. Yields in a few fields will suffer a little because of a shortage of available nitrogen. A consultant observing a field in Adair County says the yield potential is 150+ bu. per acre, but it could have been better. "I am still convinced that the field was short on nitrogen after the wet spring," he writes.
Lodging more severe in non-Bt corn
ISA's On-Farm Network will collect stalk samples for nitrate analysis on all fields in the program. "I'm anxious to take the corn stalk samples and test them and see what we find out," the consultant says.
Other scouts note in this week's report that lodging is more severe in non-Bt corn. Several plan to look more closely at roots in Bt and non-Bt fields to compare for rootworm damage.
Stalk rot could become a problem in the northwest part of Iowa where corn was drought-stressed until recently, and now some fields have received 10 or more in. of rainfall in just a week's time. Growers also need to watch for ear molds and rots (giberella and fusarium) and sprouting in the ear where husks had begun to loosen prior to heavy rains, so they can schedule harvest on problem fields first.
The ISA On-Farm Network is collecting aerial imagery on cornfields in this program. The imagery will be used to determine where to collect corn stalk samples from every cornfield in the program for pre-harvest nitrate tests. Results will be available early this winter. Imagery for soybean fields will be collected closer to the time when the soybean leaves drop.