Which of the following is a symptom of phylloxera infestation on leaves?

• A. Pale green leaf galls on the undersides of the leaves
• B. Slow, stunted shoot growth
• C. Vines die of drought
• D. Swellings on older roots

Answer: (A)

Leaf symptoms of phylloxera come from the leaf-feeding form, which creates galls on the leaf tissue. These galls, often pale green, appear on the underside of the leaf and are a distinctive sign of infestation in the leaves themselves. This is different from root symptoms, like swellings on the roots, which affect the subterranean part and overall vine vigor. General issues such as slow shoot growth or drought-related decline describe broader stress rather than a leaf-specific sign. So, pale green leaf galls on the undersides of the leaves are the best indicator of a leaf-level phylloxera problem.