Effects of the Derecho on Corn in NW Iowa

In the evening hours of July 5, 2022, a derecho moved through South Dakota into northwest Iowa.  Gusts in South Dakota were as high as 99 mph with winds that lasted up to 20 minutes.  The path of the storm’s length was about 600 miles.  A map is available to help understand the wind speed, path, and damage to property from this event.  In addition to the derecho, a tornado was also confirmed in Emmet County on the same evening by video footage of the tornado and damage that occurred based upon that event.

Most corn in the area of the storm was root lodged and some fields experienced greensnap.  The winds from the storm caused corn to lodge at a 40 to 45-degree angle in many of the affected areas.  Corn is below the V14 growth stage in most of the fields that were visited.  In the coming days corn will work to upright itself by “goosenecking” which is defined as a bend in the stalk, as the corn plant establishes brace roots to help it resume vertical growth.  Future concerns with corn that has a gooseneck is standability of corn in the future or difficulties in harvesting of the corn.

An important step is to monitor fields that were damaged by the derecho in the coming days and to notify crop insurance if your fields were affected by the derecho.  In the next several days corn that is root lodged will work to right itself to become vertical again.  Plants leaning or root lodged should stand back up in the next few days with good growing conditions.  There may be yield loss associated with the root lodging.  In a study conducted by the University of Wisconsin yields were reduced 2-6% when corn was lodged from V10-V12 and 5-15% when corn was lodged from V13-V15, read more about lodging effects on yield here. 

Greensnap is a bigger concern.  As I begin to walk fields after the storm I am seeing some fields with greensnap.  I would encourage farmers to scout their fields as corn recovers from root lodging and as they become more acessebile to scouting.  Some of the fields that looked good from the road had greensnap upon further scouting efforts.

Greensnap in Winnebago County.  (Photo taken by Gentry Sorenson)

References cited here may be helpful resources:

Carter, P.R. and K.D. Hudelson. 1988. Influence of simulated wind lodging on corn growth and grain yield. J. Prod. Agric. 1:295-299.

Ennos et al. 1993. Journal of Experimental Botany. 44:147-153.

Lipps, O.R. Mullen, and P. Thomison. 2004. Will poor root development impact corn yield potential in 2004? Corn Newsletter, Ohio State University Extension. 5 July 2004.