What is the primary function of a sticker in pesticide application?

The primary function of a sticker in pesticide application is to act as an adjuvant that enhances the adherence of pesticide droplets to the target surfaces. Stickers help to create a bond between the pesticide and the plant or surface to which it is applied, making it less likely for the pesticide to be washed away by rain or irrigation. This increased adherence can significantly improve the effectiveness of the pesticide, ensuring that it remains in contact with the pests for a longer period, leading to better pest control.

On the other hand, while the other options might suggest alternative purposes, they do not accurately represent the role of a sticker. For instance, enhancing pest resistance is not a function associated with stickers; instead, they focus on improving the application of pesticides. Likewise, a chemical attracting pests would serve a very different function, likely contrary to the objectives of pest control, and an agent that kills pests on contact describes a direct mode of action of certain pesticides rather than adherence properties. Stickers are specifically crafted for improving the application efficacy and ensuring the pesticide remains where it can do its job most effectively.