What type of adjuvant improves the spreading and sticking properties of pesticides on plant surfaces?

Surfactants are adjuvants that enhance the spreading and sticking properties of pesticides on plant surfaces. They work by reducing the surface tension of the liquid pesticide, allowing it to spread more evenly across the surface of the leaves. This improved coverage ensures that a larger area of the plant is treated effectively, leading to better pesticide absorption and effectiveness.

Surfactants also help the pesticide adhere to the plant surface, which is particularly important in preventing runoff during rainfall or irrigation. By facilitating better coverage and retention on the plant, surfactants significantly enhance the overall performance of the pesticide application.

The other options do not serve the same purpose; buffers help to stabilize the pH of the pesticide formulation, thickeners increase the viscosity of the solution, and fumigants are chemicals used to eliminate pests in enclosed environments and are not related to improving spreading or sticking properties.