What is the rule of thumb regarding spraying foliage when rain is expected soon after?

The notion that spraying can occur if the chemical dries before it rains is based on the understanding that many pesticides require time to properly adhere to the targeted surfaces and be effective. When a pesticide dries on foliage, it forms a protective barrier that allows the active ingredients to work effectively against pests or diseases. If rain falls before the pesticide has had a chance to dry, it can wash the chemical away, reducing its effectiveness and potentially leading to environmental runoff.

This rule of thumb emphasizes the importance of timing and weather conditions in pesticide application. Knowledge of the pesticide formulation, application rates, and specific weather conditions can guide applicators to ensure optimal effectiveness while mitigating risks of wash-off and environmental impact. Therefore, the correct answer accurately reflects this understanding of drying times and effectiveness in relation to impending rain.