Which weather condition detected at the application site should result in postponement or cancellation of the pesticide application?

• A. Temperature is above label limit
• B. A temperature inversion has been observed
• C. The day is clear and sunny and temperatures are rising rapidly
• D. Fog is rolling into area

Answer: (B)

A temperature inversion at the application site signals a weather pattern that makes spray drift unpredictable and deposition unreliable. Inversions create a stable layer where cool air sits near the ground under warmer air above, so spray droplets don’t disperse as expected and can travel short distances with light winds, increasing the risk of off-target contamination and worker exposure. That combination of poor deposition and high drift risk is why postponing or canceling the application is advised. The other conditions don’t carry the same definitive drift danger: exceeding the label’s temperature limit is a regulatory constraint rather than a specific weather-driven deposition issue; clear skies with rapidly rising temperatures don’t inherently create the near-ground trapping that drives drift; and fog reduces visibility but doesn’t by itself produce the stable air layer associated with high drift risk.