Dicamba Drift and the Damage We Cannot Easily Trace
By Cindy Christensen
At this year’s NNLA Summer Field Day at Kasper Tree Farm, local experts led a round table discussion on Weather, Pests, Weed and Drift. Much of the conversation focused on dicamba and the challenges it poses for Nebraska growers and landscape professionals.
Dicamba is a broadleaf herbicide. It is different from 2,4-D, though both can disrupt plant growth in similar ways. On susceptible plants, new leaves may cup, curl, or twist, and shoots may grow abnormally. Those symptoms may not appear right away. By the time a client notices distorted leaves or a grower sees stress in a field of trees, the application and the conditions surrounding it may be days in the past.
Dicamba can also move after it has been sprayed. Under certain conditions, it can volatilize, or turn to vapor, and travel beyond the application site. Nebraska Extension reports that vapor movement has been measured up to four days after application, with the greatest amount occurring in the first 24 hours. That means the weather on the day we discover damage may tell us little about when the exposure happened. For nursery growers raising trees in an agricultural state, the uncertainty can carry a real financial cost.
During the round table, one of the panelist shared an example from his own tree farm. He said the farmers immediately around his farm stopped planting dicamba-ready soybeans to help protect his trees. But farmers farther out still use them, and when those fields are sprayed, the soybeans closest to the tree farm can be injured by drift. Even with supportive neighbors, the problem can move outward from one field to the next.
Another one of the panel participants, described taking concerns about dicamba drift to his state legislature. He said opposition from large chemical companies made it difficult to gain traction. His account highlighted another challenge: when vapor crosses property lines without an obvious trail, proving where damage came from, and making the case for change, can be difficult.
So what should you do if you suspect drift damage? Document it right away. Photograph the affected plants and the wider site. Note when symptoms appeared, which plants are affected, and any nearby applications you know about. Contact the Nebraska Department of Agriculture promptly to ask about an investigation and whether samples should be tested.
Compensation for damage can be difficult to obtain when the source of the drift cannot be identified. Better protection for growers could start with time-stamped electronic application records, stronger penalties for frequent offenders, and tighter restrictions on dicamba near nurseries and other sensitive plants.
Editorial references
• Nebraska Extension, Can We Manage Dicamba Applications in 2018?:
https://cropwatch.unl.edu/2018/can-we-manage-dicamba-applications-2018/
• Iowa State University Extension, Factors Influencing Dicamba Volatility:
https://crops.extension.iastate.edu/post/factors-influencing-dicamba-volatility
• National Pesticide Information Center, Dicamba Fact Sheet:
https://npic.orst.edu/factsheets/dicamba_gen.html
• Nebraska Department of Agriculture, Pesticide Program: https://nda.nebraska.gov/pesticide