The class of adjuvants that includes materials that bind to surfaces and slow runoff in spray mixtures is:

• A. Sticker
• B. Surfactant
• C. Defoamer
• D. Compatibility Agent

Answer: (A)

The concept here is about adjuvants that increase how long a spray stays on the leaf. Sticker adjuvants are film-forming substances that bind to the leaf surface, creating a coating that helps droplets adhere and resist being washed off by rain, irrigation, or wind. This binding to the surface and slowed runoff means more of the active ingredient remains on the target for longer, improving effectiveness.

Surfactants, by comparison, are designed to reduce surface tension to improve wetting and spreading of droplets across the leaf, which helps coverage but doesn’t inherently provide lasting attachment. Defoamers reduce foam in the spray mixture and don’t affect retention on plant surfaces. Compatibility agents help keep the spray components mixed properly but don’t mainly influence how well the spray sticks to the leaf.

So, the class described is the sticker adjuvants.