Pesticides are widely used on agricultural crops, in the home, for mosquito control, in yards, and in public places. The types of pesticides commonly used include insecticides, herbicides, fungicides and rodenticides. Some of the benefits of pesticides are increased crop production, preserving produce, combating insect infestations and controlling exotic species. Pesticides are designed to be harmful to pests. When not used properly or if off target movement of pesticide occurs, pesticides can cause harm to humans, animals, or the environment.
According to Dr. Fred Fishel and Dr. Jay Ferrell from the University of Florida Agronomy Department drift is a significant legal concern in Florida. During 2009–2010, the Florida Department of Agriculture and Consumer Services (FDACS), which is the state pesticide regulatory agency, initiated 39 investigations in response to allegations of drift. Where significant drift does occur, it can damage or contaminate sensitive crops, poison bees, pose health risks to humans and animals, and contaminate soil and water in adjacent areas. Applicators are legally responsible for the damages resulting from the off-target movement of pesticides. Scientists recognize that it is impossible to eliminate drift totally but also know it is possible to reduce drift it to a legal level if the directions on the pesticide label are followed. The laws that address drift focus on preventing substantial drift. Consequently, pesticide applicators need to understand the factors influencing drift and use common-sense solutions for minimizing potential drift problems when pesticide applications are conducted.
Types Of Pesticide Drift
What are the types of drift? In Florida, drift can also have legal meaning, as there are penalties for damage caused to sensitive crops by certain types of herbicides. Off-target movement can be in the form of:
- Spray droplet drift
- Vapor drift
- Particle (dust) drift
Spray drift refers to the off-target movement of a pesticide during a liquid application. This is the result of small spray droplets being carried off-site by air movement. Spray drift occurs more frequently than the other two types of drift because almost all spray applications result in some off-target movement.
Vapor drift refers to the movement of pesticides as gaseous vapors from the target area. Some pesticides are volatile and can change readily from a solid or liquid into a gas under the right conditions. This most commonly occurs with high air temperatures. Pesticides that have volatilized into a vapor or gas may drift farther and for a longer time than they would have as spray droplets. Only those pesticides that are able to volatilize are susceptible to vapor drift. As air temperatures increase, the likelihood that these pesticides will volatilize and drift also increases.
Whenever possible, choose a pesticide formulated as a low-volatility product. Avoid applying volatile pesticides on hot days. Some products can even volatilize several hours after application, so beware if high temperatures are predicted for later in the day. Many products carry precautions against applying these products when temperatures are above 85°F or expected to reach 85°F. Remember to check label precautions for product-specific concerns about vapor drift.
Some herbicide formulations are sufficiently volatile to cause plant injury from drift of vapor. For example, 2,4-D esters may produce damaging vapors, while 2,4-D amines are essentially nonvolatile and can drift only as droplets or dry particles. Herbicide vapor may drift farther and over a longer time than spray droplets.
Particle drift refers to the movement of solid particles from the target area by air during or just after an application. These solid particles may include pesticides formulated as dust or soil particles to which pesticides are attached. Some pesticides can remain active on soil particles for long periods after they are applied. If particles are blown off the target area, contamination or damage to sensitive areas can occur. Be sure to close all windows, vents, and turn off all circulating fans, forced-air heating systems, and air-conditioning units to prevent particle drift from nearby outdoor pesticide applications from entering a building.
Drift can occur in all forms of pesticide application: using agricultural airplanes, ground sprayers, airblast sprayers, or irrigation systems. In general, drift can be influenced by factors in one of these four categories:
- Spray solution characteristics
- Application equipment
- Applicator decisions