Which type of adjuvant physically alters the surface tension of a spray droplet?

• A. Buffers
• B. Stickers
• C. Surfactants
• D. Thickeners

Answer: (C)

Surfactants are surface-active compounds that position themselves at the air–water interface of a spray droplet. By reducing the surface tension, they allow the droplet to wet and spread on leaf surfaces more effectively, improving coverage and potential uptake of the pesticide. Buffers adjust pH and don’t alter surface tension. Stickers help droplets stay on leaves by forming a film or increasing adhesion, but their main role isn’t changing surface tension. Thickeners raise the spray’s viscosity to reduce drift and improve retention, not to modify surface tension. So, the adjuvant that physically changes the surface tension of a spray droplet is the surfactant.