How does crop rotation help control nematode populations?

How does crop rotation help control nematode populations?

• A. Populations will fall if the nematode species has a narrow host range and requires a living host to survive in the soil.
• B. It eliminates nematodes instantly.
• C. It increases nematode reproduction.
• D. It has no effect on nematodes.

Answer: (A)

The main idea is that crop rotation can reduce nematode numbers when the nematode relies on a specific living host to feed and reproduce. If the nematode species has a narrow host range and requires living plant tissue to survive in the soil, switching to non-host crops interrupts its life cycle. Without a suitable host to feed on and reproduce, the nematodes can’t increase their population, so the overall numbers decline over time as existing individuals die and few new ones are produced. This gradual decline continues across seasons, reducing nematode pressure on subsequent crops. If the nematode had a broad host range or could survive in the soil without a living host, rotation wouldn’t be as effective, which is why the stated answer emphasizes the host-specific scenario. Rotation doesn’t eliminate nematodes instantly, and it doesn’t increase their reproduction, so those options don’t fit.

The main idea is that crop rotation can reduce nematode numbers when the nematode relies on a specific living host to feed and reproduce. If the nematode species has a narrow host range and requires living plant tissue to survive in the soil, switching to non-host crops interrupts its life cycle. Without a suitable host to feed on and reproduce, the nematodes can’t increase their population, so the overall numbers decline over time as existing individuals die and few new ones are produced. This gradual decline continues across seasons, reducing nematode pressure on subsequent crops.

If the nematode had a broad host range or could survive in the soil without a living host, rotation wouldn’t be as effective, which is why the stated answer emphasizes the host-specific scenario. Rotation doesn’t eliminate nematodes instantly, and it doesn’t increase their reproduction, so those options don’t fit.