Pesticide drift complaints in 1998 on a record pace
by Mike Owen

May 22, 1998 - Recent weather conditions and poor decisions by commercial and private pesticide applicators have resulted in more drift complaints, to date, than normal.  In discussions with Iowa State University Extension Field Specialists and Charles Eckermann, Pesticides Division, Iowa Department of Agriculture and Land Stewardship (IDALS), it is apparent that pesticide drift complaints are widespread across Iowa. Eckermann reports that IDALS has received 34 drift complaints, the majority coming within the last nine days.  Commercial pesticide application accounted for 30 of the complaints and four were attributed to private applicators.  While typically 30% of the complaints are dismissed, the current trend suggests that the 1998 pesticide application season could establish a new record.  In 1997, 56 drift infractions were noted.  Most drift complaints occur in June and as the use of postemergence herbicide applications increases, it is likely that there will be more problems in 1998.

The windy conditions last week contributed to the drift, but it is clear that the main problem was the decision made by applicators to apply pesticides during conditions that favor off-target movement. Because of the timing, postemergence applications have a greater potential to cause drift injury to sensitive crops, lawns and gardens (Drift injury to corn and soybeans).  Also, many postemergence herbicides have high relative activity and can injure plants at the low rates associated with spray drift.   Thus, greater caution should be exercised when considering a postemergence pesticide application. 

While drift is an inevitable consequence of pesticide application, there are a number of factors that will reduce the potential for off-target movement of pesticides to sensitive areas.  These factors are reviewed in an article that appeared on the ISU Weed Science web page (Factors Influencing Drift Potential with Glyphosate).  While applicators can make adjustments to sprayers to reduce drift potential, the most important factors are wind speed and direction.  The most important factors are wind speed and direction.  If these conditions favor drift, do not make the application.

Prepared by Mike Owen, extension weed management specialist, Department of Agronomy, Iowa State University