University of Illinois

No. 9/May 23, 1997

Herbicide Drift Remains a Concern

Long intervals between precipitation events have enabled many producers to complete corn and soybean planting in a very timely manner. A producer recently commented that the one factor that has most slowed his planting this spring is frequent high winds, which have delayed application of preemergence herbicides. Indeed, several days this spring have seen wind speeds greater than 25 miles per hour, far in excess of wind speeds indicated on many herbicide labels for safe application. Pesticide applications made when wind speeds are sufficiently high to favor offtarget movement are obviously not advisable.

With most of the corn and soybeans planted across the state, application of postemergence herbicides will soon begin. Compared to soil applications, gallons per acre often decrease and spray pressures increase for post-emergence applications, each change increasing the likelihood that drift will occur. With crops growing in adjacent fields, the evidence of herbicide drift from postemergence applications often is more noticeable than drift from preemergence applications.

We understand that with the number of acres covered by commercial applicators, applications are sometimes made under less than ideal conditions. However, there are not many "good things" that come from herbicide-drift complaints. Increasing gallons of carrier per acre and lowering spray pressures are two options to reduce the possibility of drift. Precluding drift may require keeping the sprayer in the shop until the wind dies down.

Aaron Hager, and Marshal McGlamery, Department of Crop Sciences, (217)333-4424