What is the rule of thumb regarding spraying foliage before expected rain?

The guideline regarding spraying foliage prior to anticipated rain is based on the principle of ensuring that pesticides have adequate time to adhere to the plant surfaces and be absorbed before being washed away. If the sprayed foliage dries completely before rain falls, it indicates that the pesticide has likely formed a strong bond with the leaves, which enhances its effectiveness and reduces the risk of runoff.

When a pesticide is applied to wet foliage, it can lead to uneven distribution, reduced efficacy, and potential environmental contamination as it may wash off with the rain. Therefore, ensuring that the pesticide dries entirely provides better control over the application outcomes, making it a crucial consideration for effective pesticide management.

This approach not only maximizes the potential benefits of the pesticide treatment but also takes into account the environmental implications, aiming to minimize runoff and unintended consequences.