High temperatures and low humidity usually result in what for cuticle penetration?

• A. It results in better cuticle penetration.
• B. It has no effect on cuticle penetration.
• C. It usually results in poor cuticle penetration.
• D. It only affects stomatal openings.

Answer: (C)

High temperatures plus low humidity dry the leaf surface quickly, creating a dry, waxy barrier that makes it harder for a spray to wet and diffuse into the cuticle. With rapid evaporation and shorter leaf wetness, the active ingredient has less opportunity to penetrate the cuticle, so penetration is usually poor. While warmer conditions can increase diffusion to some extent, the loss of surface moisture dominates, reducing uptake. Stomatal openings aren’t the only route for penetration, so that aspect isn’t the primary factor here.