Maryland Pesticide Applicator Category 3: Ornamental and Turf Practice Test

Waxy leaves resist wetting because their surface is hydrophobic, causing spray droplets to bead up and run off rather than spread and stay attached. Spreader-stickers act as adjuvants that lower the surface tension of the spray and help the liquid spread out into a thin film and adhere to the leaf. This improves coverage and retention on the waxy surface, making the applied product more effective. That’s why the best answer notes that the spray may not adhere well to waxy surfaces without a spreader-sticker. The other choices don’t describe this function: spreader-stickers don’t primarily change leaf color, insect feeding, or leaf burn.