Which of the following is a symptom of phylloxera infestation?

• A. Vines die of drought in patches that increase in size year by year
• B. Vine roots are covered with the insects surrounded by yellow eggs
• C. Swellings on older roots
• D. Slow, stunted shoot growth and leaf yellowing appears in around three years, the plant dies after around five years

Answer: (D)

Phylloxera damages vines by attacking the roots, which cripples the plant’s water and nutrient uptake. The most telling field signs appear above ground only after the infestation has taken hold for a while: growth slows, shoots become stunted, and leaves yellow as vigor declines. This pattern typically starts around three years after infestation, and without control the vine often dies after about five years. That progression—from slowed growth and yellowing to eventual death—best reflects the plant-level impact of phylloxera on vines on their own roots, making it the most reliable symptom to identify in a vineyard.

While root swellings can occur where the pest feeds on roots, and drought-like patches or the mere presence of insects could be noticed, those signs are less specific or more interpretive in the field. The described gradual decline and final death timeline directly ties the above-ground symptoms to the root damage caused by phylloxera, which is why it’s the best answer.