Dicamba Use in Relationship to Drift Injury on Soybeans in Southeastern South Dakota

The benefits of using herbicides have been demonstrated repeatedly, but less is known about the risks involved in the use of herbicides. Any herbicide movement out of its field of application increases the potential damage to sensitive plants and animals. Herbicides more through the air by herbicide drift. Spraying equipment, application methods, and spray additives have been developed to reduce the amount of drift. Unfortunately, none have been shown to eliminate drift without reducing herbicide effectiveness. Dicamba (3,6-dichloro-o-anisic acid) has the potential to cause drift injury. Dicamba controls certain broadleaf weeds in corn (Zea mays L.), small grain, and pasture, but soybeams are often grown near corn, drift injury to soybeans can occur from dicamba application to corn. The growth stage and variety influence the sensitivity of soybeans to many herbicides and, therefore, may influence the sensitivity of soybeans to dicamba. The extent of dicamba drift is not known. In cases of drift injury, the causative agent is difficult to identify and the effect of the drifting agent on production is difficult to determine because of inadequate comparisons. The objectives of this research were to determine: 1. Tolerant growth stages for soybeans challenged with dicamba, 2 varietal tolerance to dicamba. 3. dicamba residue by analysis of soybean foliage, and 4 the extent of dicamba use and drift occurrence in southeastern South Dakota