July 15, 2008
AMES, Iowa — The cool spring in Iowa has pushed back expected silking dates about 12 days later than usual, according to Iowa State University Extension corn specialist Roger Elmore.
"Our models show that most of the corn planted in mid-May should be silking between July 17 and 22," Elmore said.
Corn planted in May represents roughly 80 percent of Iowa's crop. Replanted acres, most of which would have been sown around June 30, are likely to see silking in mid-August.
Current weather forecasts are calling for normal conditions and precipitation over the next few weeks. If weather predictions are correct, that would be good news for farmers since corn-friendly temperatures and rainfall are critical during silking.
The late silking is likely to delay fungicide applications that Elmore said should be dependent on crop development. Pre-tasseling fungicide application can be detrimental to corn growth causing damage to ear formation.
"If farmers are spraying fungicides, they'll need to go out in the field and look to be sure their crop is beyond silking, otherwise it will be wasted money in terms of disease control," Elmore said.
Once the corn is done pollinating, yields will be closely tied to fall temperatures. Corn growth models run by Elmore show a year reminiscent of 1999 with a warm fall and a late frost could see yields near 96 percent of normal. But drastic temperature swings or an early frost could cut yields to as low as 45 percent of normal.
"The corn really needs the remainder of the growing season to resemble 1999 and not a year like 1991 when we had a late planting and an early frost," Elmore said.
A more detailed discussion of the corn growth and yield simulations can be found online: http://www.extension.iastate.edu/CropNews/2008/0710elmore.htm.