Which stimulant was widely used as an insecticide in the 1920's and 30's?

In the 1920’s and 1930s, nicotine was widely used as an insecticide. Nicotine is a substance mainly used in tobacco and similar products. It is a mild type of stimulant, increasing a person’s heart rate, which effects in increased alertness. The use of nicotine as insecticide declined because it was found not only addictive, but it causes numerous dangerous effects in human body, particularly in the lungs.