Which of the following symptoms indicates a problem with Citrus tristeza closterovirus?

The identification of poor growth flushes as a symptom of Citrus tristeza closterovirus (CTV) is important because this viral infection significantly impacts the health and development of citrus trees. CTV is known to lead to a variety of symptoms, but one of the most telling indicators is indeed a reduction in the vigor of the tree, manifesting as poor growth flushes.

When trees are affected by CTV, they often exhibit stunted growth and reduced new leaf production, which translates into less robust flushes. The virus disrupts normal physiological functions, weakening the plant's overall vitality and its ability to produce healthy foliage. As a result, instead of lush, vigorous growth, trees with CTV tend to have smaller, less healthy growth flushes.

In contrast, symptoms such as large fruit sizes, high fruit yield, and rich green foliage generally reflect healthy plant conditions. Large fruit sizes and high yields are typically associated with good plant health and the right cultivation practices. Rich green foliage suggests that the plant is photosynthetically active and healthy, which would not be the case for a plant suffering from CTV-induced problems. Thus, recognizing poor growth flushes as a symptom of this virus is crucial for effective diagnosis and management in citrus production.