Every once in awhile I get the urge to try and find something interesting in old literature, and today was one of those days. So I went over to my pile of old “Journal of Economic Entomology” journals and snatched a 1943 issue from the top. The pest issues that we had to deal with during the war years were interesting because resources were tight — we had DDT (and lead arsenate), but all of it was going to the front to protect our soldiers from lice. So scientists back home were trying new things. One which I had never heard of before today was getting a serious look: The yam bean. The yam bean is a tropical legume which has a great deal of potential as a high nutrient food crop (the root of the bean is what is edible, not the seeds). The food part is interesting to me, but more interesting is the fact that a dust could be made from grinding the beans into a powder which would kill insects. After looking through some articles I discovered that the primary source of toxicity in the yam bean is rotenone and some similar chemicals. I’m not a big fan of rotenone, still, this plant is fascinating. An edible root and seeds which can be used very effectively as an insecticide. Why wasn’t this plant more common 50 or 100 years ago? What other plants are we missing out there which are useful?
I love coffee, but I’m not a big coffee drinker. On average I probably consume a cup of coffee every week or two. Why don’t I drink it more often? For a few reasons: First, I’m too jumpy/jittery/nervous to begin with and I don’t need this stuff making it worse, second, it tends to upset my stomach if I haven’t had a meal beforehand, and third, while I like regular coffee, the stuff that I really love are those insane fru-fru coffee drinks that you can only get at specialty shops for five or six bucks — which seems like a waste of money to me. As you may have guessed, at this very moment, I have an overwhelming urge for a vanilla latte and so, in lieu of that, I have decided to submit this post.
Anyway, as most of you know, coffee is a horticultural crop, and so are most of the other sources from which most of us obtain our (legal) chemical stimulants like chocolate and tea. What most people don’t realize is that the stimulants in chocolate and tea are actually somewhat different than caffeine. Chocolate does contain some caffeine, but its major stimulant is the closely related theobromine (which doesn’t actually have any bromine in it…). Tea (which also has very low amounts of caffeine), on the other hand contains the stimulant theophylline which is, again, closely related to, but not the same as, caffeine.
What blows me away about caffeine is how toxic it is. If caffeine were a pesticide it would need to be labeled as category 2 (there are 4 classes with 1 being the most toxic). Its LD50 (in other words, the amount of this chemical that, if fed to a person, would have a 50% chance of killing him/her) is estimated at about 75 milligrams per pound that a person weighs. According to Starbucks website, one of their tall vanilla lattes contains about that much caffeine, and so you could assume that a 150 pound person could kill themselves by drinking about 150 lattes (or 150 of the smaller cups of espresso from which the coffee is made). Additionally, though findings are inconsistent, caffeine has been linked to certain cancers. The current thinking is that it may affect hormone levels in the body which, in turn, influence hormone related cancers like breast cancer, etc. This research is far from conclusive, but it is concerning.
OK, so here’s the thing that’s interesting to me. There is a small but real contingent of people out there who want to ban the herbicide 2,4 D (I picked 2,4 D randomly – I could have picked Round-up, Sevin, or any other pesticide – but I was thinking of summer, and so 2,4 D, the most commonly used turf herbicide, is what I chose). I’m no fan of 2,4 D and would love to see it used less frequently than it currently is, but it is a useful herbicide, particularly in the production of grassy crops (like corn). In lawns its overuse borders on the insane.
Opponents of 2,4 D would like to see it gone, in large part, because of its toxicity and potential to cause cancer. And, indeed, there are some studies that show that 2,4 D has the potential to cause cancer, though these findings are inconsistent and ultimately inconclusive. Additionally, in terms of 2,4 D’s LD50, it’s about 170 milligrams per pound that a person weighs – over two times LESS toxic than caffeine. I’m not going to bother figuring out how much 2,4 D would be in an average glass of 2,4 D because, well, I’ve never been served a cup of 2,4 D before and hopefully I never will. (If you’re curious as to how much 2,4 D would be in a cup of spray if you scooped it right out of the spray tank — then about 50 mg is a good estimate though it could be higher or lower depending on a lot of factors).
Anyway, this leads me to a ton of further questions, the most important of which is, without doubt, do anti-pesticide activists who fear the health dangers posed by 2,4 D drink coffee?
For those of you interested in these types of questions I encourage you to look over this article: http://www.marshall.org/article.php?id=73 It is posted on the website of a conservative group (which will probably alienate some of you and make others happy) – but it was originally published a number of years ago in a well respected journal and is one of my favorite articles ever in terms of getting the old brain thinking (Please don’t get the idea that I agree with everything in the article – I do not). Bruce Ames, one of the authors, is what we call in academia a “heavy hitter” and so, even if you don’t agree with what he says, his words are well worth reading.
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.