Pests can eat crops or damage them so they can't be sold.
Pesticides are used to kill pests that reduce crop yield.
The assure that crops won't be damaged. Fast and accurate to apply. Instant results.
They can harm other wildlife.
Killing the pest may affect biodiversity.
Pesticides can leech into the soil and possibly pollute rivers or surrounding habitats.
Pests can become immune.
Biological control is introducing a predator into the environment with the crops to kill the pests.
Cheep. Self regulating.
The predator may enter the wild and effect the biodiversity.