Two threats to herbicide applications are drift and volatilization. While they may seem similar, they are quite unique and require different attention to ensure that neither occur.
Drift occurs during the herbicide application. It is the unintentional, off-target application of herbicides. This can lead to damage of surrounding crops as well as an ineffective herbicide application.
There are several factors that can lead to herbicide drift, including:
- Severe Temperatures: Ideal temperatures for herbicide-use range from 65 degrees F to 85 degrees F.
- High Wind Speeds: Herbicide labels specify optimal wind conditions for application. If a grower goes off-label, their risk of drift increases.
- Small Droplet Size: Smaller droplets are more likely to be carried away by the wind than larger droplets. Herbicide labels will also specify optimal droplet size to decrease drift.
Herbicides are most effective when applied in high humidity and with wind speeds of about 10 mph or less. Ensure that the application nozzles are on the correct setting to produce optimal droplet size to minimize drift. The position and height of the boom are also listed on the herbicide label. With the boom being closer to the crops, the distance the droplets can travel is reduced.
Volatilization is the movement of herbicide vapors through the air following an herbicide application. Similar to evaporation, volatilization occurs when the herbicide residue changes from a solid or liquid to a gas or vapor. Once vaporized, the vapors can be carried long distances by the wind, possibly damaging surrounding crops as well as causing an ineffective herbicide application.
The risk of volatilization increases when:
- Herbicides are applied to inert, non-absorbent surfaces like rocks or pavement,
- Temperatures are high,
- Humidity is severe and
- Herbicide formulations are potentially volatile.
Reducing the risk of volatilization is vital in order to have a successful herbicide application. Growers should be sure to avoid unfit conditions including high temperatures and humidity. Identifying if the target has a non-absorbent surface or if the herbicide formulations may be volatile can help growers make proactive decisions regarding tank mixers.
Herbicide specs are not one-size fits all. When it comes to avoiding drift and volatilization, herbicide labels are king. By following the label closely, growers will be able to maximize their herbicide applications and lower drift and volatilization.