well, i have this thesis about making an organic insecticide out of spices and nicotine. i could just use a citrus fruit to lessen its bad odor…anyhow, i decided to use spices because well, like for example, when you eat something spicy, it has like a heating or somewhat painful sensation to the tongue. So i thought maybe it can also be effective in killing insects. but my problem is, what's in spices that gives that heat or pain, and what substances are common in other commercial chemical insecticides?thanks a lot!
this would be a great help on my thesis…
uhm specific spices i want to use: crushed chili pepper, garlic powder and bay/peppermint leaves…
^^

Spices may or may not have insecticidal properties. I believe that nicotine or tobacco does.

This could work as a home made insecticide — bring an old pot of water to a boil, turn off heat and put in a cheap crushed cigar. Let this cool down them strain thru a cheesecloth. The remaining liquid (after it is cooled to room temp) can be sprayed on affected plants.

One substance common to some commercial pesticides is found in crysamthmums. You would need to grind the flowers up until very fine then add to water.

As for amounts needed you would have to experiment. If you decide to go ahead with this please be careful.