Repellent

Repellent was a man-made substance which could repel pests. 
According to the Thirteenth Doctor, spider repellent could be concocted from peppermint and tea tree oil diluted with water. (TV: Arachnids in the UK)
On 11 April, 4530, the human-Zarbi wars came to an end when Earth faced an insect-repellent shortage. (PROSE: Time Traveller's Diary)
Category:Bioweapons
Category:Human technology