What is the role of weather in pest development and spray timing?

• A. Weather has no effect on pest development.
• B. Only wind speed affects spray timing.
• C. Temperature alone determines all pest life cycles.
• D. Temperature and humidity influence pest life cycles and fungicide efficacy; timing sprays to stages and favorable conditions improves control.

Answer: (D)

Weather governs both how pests grow and how well sprays work. Temperature sets the rate of pest development and which life stages are vulnerable, while humidity and leaf wetness influence survival, disease pressure, and how quickly pests progress. Sprays are most effective when applied under conditions that favor product deposition, uptake, and persistence, and when timed to the pest’s susceptible stage. Extreme heat or drying conditions, heavy rain, or poor coverage can reduce efficacy, so aligning timing with favorable weather and pest biology yields better control.