Foliar treatments are most effective when applied to which condition?

• A. Fully developed foliage of an actively growing plant
• B. Leaves just unfurled in spring
• C. After rainfall
• D. During dormancy

Answer: (A)

Foliar treatments work best when the plant is actively growing and the foliage is fully developed because the leaf surface is ready for absorption and the plant’s physiology supports uptake. Fully developed leaves provide ample surface area for spray contact, and when the plant is actively growing, stomata are open and cells are metabolically active, allowing better absorption and movement of the chemical within the leaf and into the plant where it’s needed. If leaves are just unfurled, the cuticle and waxes may still be changing as the leaf finishes expanding, which can hinder absorption. After rainfall, sprays can be washed off, reducing contact time and effectiveness. During dormancy, there’s little or no active growth or stomatal activity, so uptake and translocation are minimal.