Spray drift. News articles about damage caused by spray drift seem to pop up regularly, almost as daily reminders, during the summer months, writes PrecisionAg.com contributing writer Reinder Prins. Whether it be dicamba-related issues in those states of the U.S. where dicamba-tolerant soybeans are grown, 2,4-D related issues in the Australian cotton-growing region, or any number of other events that are reported on in the news on a regular basis, spray drift seems to be omnipresent.
Spray drift, the airborne movement of chemicals as droplets, particles or vapor, can have many causes but the main ones are:
- Wrong droplet size; small droplets drift easier.
- Wrong conditions (inversion, wind too low or too high).
- Wrong formulation used; ester instead of amine formulations for example.
Chemical drift can have far reaching consequences, from not properly spraying the field that you intend to spray, to damaging a neighbor’s crop, or even creating a health hazard for humans and animals. In the long run, the consequences of repeated spray drift can mean that growers lose access to key weed control tools. Examples of this are repeated calls to ban or restrict the use of 2,4-D in Australia’s cotton growing areas, with similar dicamba issues in certain states of the U.S. This recently became even more real for many growers as the scary prospect of losing glyphosate played out as Brazil temporarily banned the use of this valuable herbicide, even though there was no scientific justification for the decision. Growers and suppliers all over the world were relieved when this initial ruling in Brazil got overturned, but it was a good reminder that it is up to us to demonstrate responsible use so that they are not taken away, leaving us with more expensive / time-consuming options.
As shown above, there are a multitude of reasons that can cause off-target drifting, but all these reasons lead back to one common theme: Operator knowledge. Droplet size for example is a factor of pressure and nozzle type, weather factors can be measured with a weather meter and product suitability information can be found on product labels. Identifying inversions however is not that easy and it takes some practice and experience. In most areas, spray operators have to successfully complete a training course before they are allowed to operate a spray rig, but these courses only really teach the basics and operators need more experience and on-the-job training in order to become proficient.