Which late-evening time is sometimes chosen for ULV applications to balance pest activity and drift?

• A. Noon
• B. 6:00 AM - 8:00 AM
• C. 10:30 PM
• D. Half hour before sunset

Answer: (C)

Timing ULV applications is about matching when pests are active with when the air is quiet enough to keep droplets where they’re targeted. After sunset, the atmosphere usually becomes calmer and more stable, which reduces drift of the ultra-fine droplets. Those tiny particles tend to stay closer to the ground in still air, increasing the chance they contact pests that are still active at night. Many flying or nocturnal pests, such as certain mosquitoes, remain active in the late evening, so applying around 10:30 PM hits that activity window while drift is minimized. In contrast, midday tends to be windier and warmer, which can push droplets off target; just before sunset can still have noticeable air movement; and early morning can also have greater turbulence.