Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


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July 12, 2011






            I never thought I'd live to see a storm that rivals the 1998 storm that had 100 mph winds in a 20-mile+ swath over 100 miles long, but the storm Monday morning apparently had straight line winds of up to 120 mph in a swath of 20 miles or so wide and traveled from south of Ames up through Tama, Benton, Linn, and Jones counties and into Dubuque county. There is likely over 100,000 acres of corn that is flattened, in addition to thousands of trees snapped off, grain bins blown over, and farm buildings destroyed. . The good news is it looks like the vast majority of the corn is flat because of root lodging and not green snap. I've looked at fields from Martelle in Jones County over through Vinton to Toledo, and every flattened field I looked at had very little green snap. With the 1998 storm there was a tremendous amount of green snap, which resulted in large yield losses. The 1998 storm occurred on June 29, so much more of the corn was in the more vulnerable V10-V12 stage when stalks are more brittle. Most of the corn is in the V14-V18 stage now, so less subject to green snap. The heavy downpours that occurred at the same time may have also helped by saturating the topsoil and allowing roots to shift rather than breaking stalks.


With green snap, most research has shown a 1:1 relationship between percent green snap and percent yield loss (50% green snap results in 50% yield loss). More information on green snap is in Roger Elmore's article at With root lodging the yield prospects are much better, with perhaps less than 20% yield loss even with 100% root lodging. The stalks will straighten back out (or at least the upper stalk will straighten), so hopefully there will not be a large affect on pollination. It will be a real challenge at harvest time, but at least it looks like there will be corn to harvest. A study done in Wisconsin showed yield losses of about 10-20% when corn was totally flattened at V14-V18, where most of the affected corn is now. More details are in an ICM article from 2002 about a similar wind event in Dallas and Guthrie counties


            There is also a lot of seedcorn affected in the storm damage area. In general, the lodging is not as extensive in the seed fields, because the corn is shorter, but unfortunately there are many seed fields where the lodging is great enough so that it is difficult to impossible to walk through the fields. This means they cannot be detasseled, so they are a total loss. Many seed fields may be disked up.


            The main thing to do at this point is check with your insurance to see if wind damage is covered. Many policies do not cover wind, or if they do it is only covered if there is green snap. There will be a crop storm damage informational meeting south of Vinton at 3:00 p.m. on Thursday – see details below.





Crop Storm Damage Meeting

Thursday, July 14

3:00 PM

John Olson Farm Site

Location:  2.5 Miles South of Vinton

Northwest Corner of Highway 218 and 63rd Street

(watch for signs)

Topics: Learn about what to expect from recent storm damage to crops, management decisions, livestock feed options, and Farm Service Agency Programs. 


Jim Fawcett, ISU Extension Field Agronomist

Jim Jensen, ISU Farm Management Specialist

Denise Schwab, ISU Beef Program Specialist

Patrick Derdzinski, Benton County Farm Service Agency Director




JULY 19, 2011

Details will be posted soon at


Corn Nematode Field Day

Cedar County Coop – West Branch

Evening of August 2



Greg Tylka will discuss research evaluating seed treatments for nematodes that feed on corn.

Details to follow soon.



If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: July 12, 2011
Contact: Jim Fawcett

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