Which adjuvant increases the viscosity of spray mixtures?

• A. Foamer
• B. Humectant
• C. Surfactant
• D. Sticker

Answer: (D)

Viscosity in spray applications refers to how thick and sticky the spray residue becomes after it hits the plant surface. A sticker adjuvant contains film-forming polymers that form a cohesive layer on the leaf, making the residue thicker and more adherent. This sticky film on the leaf surface increases the effective viscosity of what remains after spraying, helping droplets resist being washed off by rain, dew, or irrigation and improving how long the product stays where it’s needed.

Foamers create foam, which doesn’t raise the thickness of the residue on the leaf. Humectants help keep the spray moist but don’t significantly increase viscosity. Surfactants lower surface tension to improve wetting and spreading, so the spray covers more area, but they don’t create a thick, sticky film that raises viscosity.