Biological Control
Biological control is using one living thing to stop a pest that harms crops or wild plants.
Think of it this way
A jar of fruit has gnats flying around it. You drop in a small spider, and it catches the gnats one by one. The fruit stays safe because the spider eats the pests. One living thing controls another, and the jar stays clean.
Explaining biological control by grade level
Some bugs eat plants that we do not want. Other bugs can eat those bad plants. People let the helpful bugs loose to do the job. This way, the bad plant goes away without using sprays.