Concept:Viral diseases in crops cannot be cured by chemicals, so prevention depends on choosing planting materials that resist infection.
Explanation:Treating seeds with fungicides only controls fungal diseases, not viral diseases.
Practicing crop rotation helps reduce soil-borne pests and diseases, but it is not the most effective method against plant viruses.
Regular spraying of crops mainly controls insects, fungi, or bacteria, and it cannot prevent virus attack.
Planting resistant varieties is the most effective method because these crops have genetic traits that stop the virus from multiplying or spreading.
Therefore, the best preventive measure against viral diseases is to grow crop varieties that are resistant to the virus.
Answer:Planting resistant varieties