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, widely 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)