Which type of adjuvant increases the viscosity of spray mixtures?

• A. Sticker
• B. Extender
• C. Thickener
• D. Emulsifier

Answer: (C)

Adjuvants modify how a spray behaves on plant surfaces, and viscosity is a measure of how thick or resistant to flow the spray is. A thickener adds substances that increase internal friction in the liquid, making it more gel-like and less likely to run off a leaf. That higher viscosity helps the spray stay on the target longer, improving contact and reducing immediate runoff or drift. Stickers enhance adhesion to the leaf but don’t primarily raise thickness; extenders influence coverage and dilution aspects rather than flow resistance; emulsifiers stabilize mixtures of oils and water rather than changing viscosity. So, the adjuvant that increases viscosity is the thickener.