Which method is NOT effective in controlling Citrus tristeza closterovirus?

Neglecting infected plants is not an effective method for controlling Citrus tristeza closterovirus. This approach allows the virus to continue to thrive and spread in the environment, as the infected plants can act as reservoirs of the virus, leading to further transmission to healthy plants. In contrast, effective control measures include quarantine measures, which help to prevent the introduction of infected plants into new areas; grafting with disease-free material, which enables the propagation of healthy plants; and planting resistant varieties, which provides a proactive strategy to combat the virus by using plants that are less susceptible to infection. Each of these strategies targets the spread or impact of the virus in a manner that actively promotes healthy plant populations.