What method is least effective for treating pests when it's drizzling?

Spraying is the least effective method for treating pests when it is drizzling due to the way liquids behave in wet conditions. When pesticide solutions are sprayed during light rain or drizzle, the moisture can significantly dilute the pesticide, reducing its efficacy. Additionally, the rain can wash away or disperse the pesticide before it has a chance to adhere to and affect the target pests.

In contrast, dusting involves applying a dry formulation that remains effective even in moist conditions, as it does not rely on liquid adhesion. Trapping is also less affected by weather conditions, as it captures pests without the need for a chemical application. Fogging can be somewhat impacted by rain, but it creates small droplets that can still penetrate areas where pests may hide.

Understanding the limitations of different pest control methods in varying weather conditions is crucial for effective pest management. This is why spraying is generally not advisable when it is drizzling, making it the least effective option in these circumstances.