Which of the following cultural practices aids in managing viruses in crops?

Frequent rotation of crop varieties is an effective cultural practice for managing viruses in crops because it helps to disrupt the life cycles of virus vectors and pathogens. By alternating the types of crops planted in a specific area, especially those that are resistant to specific viruses, farmers can reduce the population of virus-carrying insects and limit the spread of viruses. This practice helps to break the chain of infection, as pests that transmit viruses may not find suitable hosts in rotated crops, thus decreasing the incidence of viral infections.

In contrast, the other practices provided do not effectively address the management of viral pathogens. Inoculating with beneficial nematodes primarily targets plant parasitic nematodes and is not a direct method for controlling viruses. Planting closely spaced crops can increase competition and stress among plants, making them more susceptible to viral infections and vector infestations. Lastly, applying high nitrogen fertilizers can promote lush plant growth, which may inadvertently attract more insect pests that can transmit viruses, thereby exacerbating the problem rather than solving it.