People often ask me about the most dangerous pesticides — the ones which they should be careful to avoid. There are lots to choose from: Di-syston (aka disulfoton) is really bad. Rotenone has some potential problems that make it scary, as does copper sulfate. But for my money the worst thing out there is something that isn’t even supposed to be used as a pesticide (at least not anymore) but which finds its way into our gardens thanks to recommendations from people like Jerry Baker: Tobacco.
Despite its obviously “natural” origins, tobacco isn’t allowed by organic growers because of its drawbacks which I’ll mention below, but because it finds its way into so many “how-to” books it’s definitely worth knowing about this beast.
It’s easy to buy chewing tobacco, mix it with a little water, and apply it to whatever aphids or other insects that you see. What’s even better is that tobacco really does work (just like Jerry says!). In fact, for some things it works great. For example, I’ve tried all kinds of barriers against slugs, and tobacco is the one that works the best, hands down — copper is kinda OK, diatomaceous earth takes a while but works fine — but man, tobacco really throws slugs for a loop. Watching a slug try to go through a pile of tobacco is terrible (and yet morbidly entertaining!) First, the slug approaches the tobacco at a snails pace (the snail is a close relative of the slug!) Then the slug touches the tobacco….and then the fun begins! The slug starts to move really fast — literally mouse walking pace — and then it stops — and then it shakes — and then it dies. This all happens within four minutes. The slugs in the picture below are all dead.
Despite my success I have a hard time recommending tobacco for slugs for two reasons. The first is that it can carry plant diseases which can cause some major problems, and the second is that some dogs like to nibble at the tobacco — and they won’t let you know they’ve nibbled it until you let them back into the house (if you know what I mean)!
When a tobacco spray is used for insects the process is a bit different than just placing tobacco on the ground. First, you mix tobacco with water, let it soak for awhile, filter the water out, and then spray it on the insects. In the old days — the 1800s when this type of spray was popular — they would mix about a pound of tobacco with a gallon of water. Jerry usually recommends much less. The problem with recommending less than this is that at lower concentrations it doesn’t work nearly as well — but you really wouldn’t want to apply more because then the spray starts to get dangerous (because of higher nicotine concentrations). So it’s a catch-22. Don’t underestimate the toxicity of nicotine! Also avoid underestimating the nastiness of the plant viruses that this stuff carries.
So what should you use instead? A good insecticidal soap, or a spray with water are what I like to recommend. If you must use something stronger then look for an insecticide with the active ingredient permethrin and follow the labeled instructions carefully (also make sure that the insect you want to control is on the label — if you can’t identify the insect you’re trying to control, or if that insect isn’t on the label, then don’t use a pesticide). For slugs my favorite pesticide uses the active ingredient iron-phosphate.