Tobacco is definitely bad for humans, but it can be imminent death for insects.

The wild tobacco plant (Nicotiana attenuata) is a desert weed that has evolved a pair of useful defense mechanisms to combat insect predators.

[photo credit: Danny Kessler]

Its first line of defense is a poisonous neurotoxin, nicotine, which is effective against a wide array of insect species. Nicotine was once commonly utilized as an insecticide, but now nicotine-analogs are produced and distributed world-wide to battle  insect infestations (e.g.: Imidacloprid — probably the most widely used insecticide in the world — for agriculture, animals (fleas and ticks), gardens, home protection, et cetera).

The tobacco plant’s secondary line of defense is a release of terpenes (herbivore-induced plant volatiles (HIPVs)), which are phytodistress signals synthesized and released in response to an insect assault.  If insects graze on tobacco leaves, the bug’s saliva triggers the production of terpenes from chewed and untouched leaves. For example, when the nicotine-resistant tobacco hornworm (Manduca sexta) grazes on the tobacco plant, the plant emits terpenes that attract the big-eyed bug (Geocoris paliens), which just happens to be a predator to the hornworm (and consumes the hornworm and its eggs).

I think from now on I’ll be extra kind to plants, just in case there is a terpene that attracts grizzly bears.