Which biological control agent is used against soil-dwelling pests such as grubs?

• A. Lady beetles
• B. Parasitic wasps
• C. Beneficial nematodes
• D. Mycorrhizal fungi

Answer: (C)

When dealing with soil-dwelling pests like grubs, you want an enemy that lives in the soil and can actively hunt and kill underground insects. Beneficial nematodes fit that role perfectly. They are microscopic, parasitic worms that move through moist soil and enter grub bodies. Inside, they release symbiotic bacteria that quickly kill the grub, and the nematodes then reproduce inside the cadaver, producing new generations that continue searching for more grubs. They’re typically applied as a soil drench or through irrigation and are relatively safe for humans, pets, and many non-target organisms when used correctly. They also work under the soil where grubs reside, which is why they’re effective for this purpose.

In contrast, lady beetles primarily hunt above ground, feeding on pests like aphids on leaves. Parasitic wasps attack pests in or on plants, often not targeting the underground life stage of grubs. Mycorrhizal fungi improve plant nutrient uptake and soil health but do not control grub populations.