Jenny Rhodes, Principal Agriculture Agent
University of Maryland Extension, Queen Anne’s County
This is a friendly reminder to be mindful of the potential for temperature inversions in low-wind conditions that can cause extensive spray drift, especially if there are known sensitive crops and apiaries in your area. The photos below show grape vines that have recently been damaged by spray drift.
A temperature inversion exists when air at the ground level is cooler than the temperature of the air above it. The sideways air movement can cause spray droplets to be suspended and carried long distances before settling out and possibly causing damage or harm.
When do inversions occur?
Any time of the day and at any height above the ground, but most often during the early evening hours as the ground temperature begins to cool and the warm air has already risen. This may persist until the ground starts to warm mid-morning.
How do I know if there is an inversion?
Observing the movement of dust or smoke is a good indicator. Dust or smoke will hang in the air when an inversion is present or developing. Thermometers can be used at ground level and high above the ground to compare the temperature. If the ground level temperature is lower, there is an inversion.
- For more information about temperature inversions: https://blog.umd.edu/agronomynews/2017/07/26/pesticide-drift-and-temperature-inversions/
- To check for sensitive crops and apiaries in your area: https://mda.maryland.gov/plants-pests/Documents/PesticideSensitiveCropLocatorFieldWatch.pdf
- Sign up for Drift Watch: https://driftwatch.org/signup#applicator
- FieldWatch Map: https://md.driftwatch.org/map
Information from the Maryland Pesticide Applicator Core Manual.
