Which organism is used as a biological control for mosquitoes in the base pond?

• A. Filling in the low-lying areas with dirt.
• B. Spraying the base with low doses of malathion.
• C. Depositing larvacide in the stagnant water areas.
• D. Gambusia minnows in the base pond.

Answer: (D)

Biological control relies on a living organism to reduce a pest population. For mosquitoes in a base pond, introducing Gambusia minnows, or mosquito fish, provides a natural predator that feeds on mosquito larvae in the water. By consuming the larvae as they develop, these fish help lower the number of mosquitoes that survive to adulthood, making them an effective, targeted approach in stagnant, aquatic habitats where larvae concentrate. They’re often preferable to broad-spectrum chemicals because they act specifically on the larval stage and can persist in the environment without repeated chemical applications. The other options don’t fit this concept: altering the landscape changes habitat rather than adding a living control agent, spraying a chemical insecticide kills insects but isn’t a biological control, and applying a larvicide that's not an organism also doesn’t involve introducing a living predator to the pond.