During my early assignment as a farm advisor, I received a complaint of sudangrass “burned down” by a grower. This problem was later discovered that it was caused as a result of herbicide drift from the nearby spray of a round-up ready sugar beet field sprayed under windy conditions. Regardless of the large gap between the two crop fields, the drift has damaged a large area of the sudangrass crop.

After having a tour of the fields with one of my colleagues and observing the effects, I decided to write this article believing that it may serve as warning; learning and taking necessary measures to avoid such problems. I believe that this may be an important piece of information for growers, pest control advisors and pesticide applicators in minimizing or avoiding herbicide drift.

An herbicide is simply defined as a chemical substance used to destroy or inhibit the growth of plants; especially weeds. Therefore, it can actually kill any plant unless there are selective control properties within the herbicide. It must also be known that the term weed is user specific, because someone’s weed could be the other person’s crop.

What is herbicide drift? Herbicide drift is movement of an herbicide away from the target area. There are three main forms of herbicide drift; droplet drift, vapor drift and particulate drift. Droplet drift is the most common cause of off-target damage, but the easiest to control because under good spraying conditions, droplets are carried down by air turbulence and gravity, to collect on plant surfaces. Particle drift occurs when herbicide carriers evaporate quickly from the droplet leaving tiny particles of concentrated herbicide and may damage susceptible crops up to 30 km from the source. Vapor drift is confined to volatile herbicides such as 2,4-D ester. It arises directly from spray or evaporation of herbicide from sprayed surfaces and may occur hours after the herbicide has been applied.

It should be noted that the main goal in herbicide use is to maximize the amount reaching the target and minimize amount reaching off-target areas. Reaching the target would maximize the effectiveness of the herbicide, while reducing damage or contamination of crops and/or areas. Since all pesticides are capable of drifting, one who sprays these materials has the moral and legal responsibility to prevent drift and hence, avoid contamination or damaging of crops and sensitive areas.