What type of adjuvant is used to increase the viscosity of spray mixtures?

The correct choice is the thickener, which is an adjuvant specifically designed to increase the viscosity of spray mixtures. Thickeners are commonly used in pesticide formulations to enhance their performance by slowing down the movement of the spray solution, thereby allowing for better coverage and adherence to target surfaces. By increasing viscosity, thickeners help reduce drift and improve the overall application efficiency of the pesticide, ensuring that it remains on the target area longer and is less likely to wash off or evaporate.

In contrast, surfactants primarily lower the surface tension of the liquid, promoting better wetting and spreading of the solution on the target. Stabilizers are used to maintain the dispersion of ingredients in the mixture and prevent separation, while binders help adhere pesticide particles to the target surface. Each of these functions plays a critical role in the efficacy of pesticide applications, but when the goal is specifically to enhance viscosity, thickeners are the appropriate choice.