1940's and 50's Huge increase in number of pesticides available. 1960's Rachel Carson wrote The Silent Spring - the first wide read warning of pesticide overuse. Realized the critical link of insects in the food chain. Instead of annihilating the insect population - manage the pest. Plants have defense mechanisms - exploit those.
Pheromones are insect hormones.
Spot treatments - treat only infected areas. Manages pests, but allows beneficials to exist Prior to the 1960's pesticides had a pretty good reputation. Due to mosquito transmitted diseases, the French lost 30,000 people in the 1800' s trying to build the Panama Canal. Americans finished the project in 1914. The Bubonic Plague is credited for killing over 65 million people - transmitted by fleas on rats.