I've read some advanced organic gardeners grow N. rustica (a wild form of tobacco) and make a tea out of it which has a very high nicotine concentration, and then spray it as a natural pesticide. Care has to be used, however, since the nicotine can easily absorb through skin, so protective gloves should be worn (and like any pesticide it should be regarded as a poison, ingestion could cause poisoning, concentration of nicotine is a lot higher than ordinary tobacco).
Pyrethrin is derived from chrysanthemums. I've you've ever noticed, insects don't normally attack chrystanthemums.