Flexstar carryover
by Bob Hartzler

May 12, 2000 -  With the increased use of Flexstar (fomesafen) in recent years we have seen a few situations where rotational corn has responded to carryover from this herbicide.  Corn damaged by fomesafen exhibits veinal chlorosis or necrosis, resulting in striped leaves.  Destruction of the tissue near the leaf midrib may cause the leaf to collapse at the midrib.  The sample in the photos was received in the mail today (Friday May 12) from east central Iowa and demonstrates the characteristic striping of leaves.

The Flexstar label carries a 10 month rotation interval for corn.  With late applications made for waterhemp control and the early planting of corn this spring there will be numerous fields where this rotation restriction is pushed to the limit.  In addition, many areas of the state had below average rainfall following the application season which could result in reduced herbicide degradation.   While we anticipate a potential for more cases of fomesafen carryover, it is important to note that corn normally recovers quickly from this injury.  We are unaware of any situations in Iowa where the injury has persisted long enough to pose a significant threat to yield potential.  Also, this response has only been observed on a small percentage of fields treated with Flexstar or Reflex.  The purpose of this article is to familiarize persons to the symptoms associated with this product, rather than forecast widespread problems.

- Field example of Flexstar carryover injury

Prepared by Bob Hartzler, extension weed management specialist, Department of Agronomy, Iowa State University