Crop rotation can reduce disease pressure only if:

Crop rotation can reduce disease pressure only if:

• A. Spores blow in from distant fields each year
• B. The pathogen survives locally in soil or crop debris
• C. The disease is caused by a virus
• D. The disease has a very wide host range

Answer: (B)

Crop rotation reduces disease pressure by breaking the pathogen’s ability to build up in the field. It works best when the pathogen can survive locally in the soil or crop debris between seasons. If the pathogen persists in the field itself, rotating to a nonhosts or less susceptible crop reduces the amount of inoculum available to infect the next crop, so disease pressure drops over time. If spores or inoculum are constantly blowing in from distant fields, or if the disease is carried by a virus or can persist despite rotation, then simply changing crops won’t cut the local source of inoculum as effectively. A pathogen that relies on local survival in soil or debris is the situation where rotation genuinely lowers disease pressure, which is why this option is the best answer.

Crop rotation reduces disease pressure by breaking the pathogen’s ability to build up in the field. It works best when the pathogen can survive locally in the soil or crop debris between seasons. If the pathogen persists in the field itself, rotating to a nonhosts or less susceptible crop reduces the amount of inoculum available to infect the next crop, so disease pressure drops over time.

If spores or inoculum are constantly blowing in from distant fields, or if the disease is carried by a virus or can persist despite rotation, then simply changing crops won’t cut the local source of inoculum as effectively. A pathogen that relies on local survival in soil or debris is the situation where rotation genuinely lowers disease pressure, which is why this option is the best answer.