Pesticide

A pesticide is something which deters or kill pests. A class of pesticide, insecticide, was used against insects.

In the early 1960s, Forester committed murder to cover up the far-reaching and dangerous side effects of DN6, the insecticide which he had developed. DN6 worked so effectively that, if used, it would have caused serious harm to Earth's ecology. (DW: Planet of Giants)

In the 1970s, an improperly mixed pesticide spray caused insects to grow to giant sizes and start rampaging across the countryside. The Third Doctor discovered a formula which returned the insects to their normal size, ending the threat. (TVC: Insect)

In the 2000s, the Pharm developed pesticides from captive Weevils. (TW: Reset)

In 2035, World Pest Control sprayed the Caterpillar Men with a pesticide which was non-lethal to humans. (TVC: The Caterpillar Men)