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Sunday, January 23, 2011

Slugging Coffee

Tamar Haspel, who writes the very fun blog Starving Off The Land, once wrote that she was disinclined to bait slugs and snails with beer because it was too much like buying them a beer.  When you factor in who-in-their-right-mind-would-bait-them-with-the-good-stuff,-so-let's-just-go-to-the-store-and-get-a-sixer-of-Old-Milwaukee, you realize that she's right. You are buying them a beer, which seems a ludicrous thing to do when they are your enemy, after all, and one with whom diplomacy has no value.

But would you buy them a cup of coffee?  A very dilute cup of coffee?

It turns out that even in very dilute solution, caffeine is a great poison for slugs and snails.  To wit:  "In this study, caffeine is shown to act as both a repellent and toxicant against slugs and snails. This research is the first to document the potential of caffeine as a molluscicide. A drench treatment using a 1% or 2% solution of caffeine caused 100% of slugs (Veronicella cubensis) to exit treated soil, and the majority of these slugs subsequently died from caffeine poisoning. A 2% solution of caffeine applied to the growing medium of orchids killed 95% of orchid snails, (Zonitoides arboreus), and gave better control than a liquid metaldehyde product representing the standard commercial control for this pest. Using leaf-dip bioassays, we discovered that slugs tended to avoid feeding on plant material treated with caffeine solutions  0.1%, and caffeine solutions as low as 0.01% significantly reduced overall feeding by slugs. Due to concerns about chemical residues, available molluscicides generally cannot be applied directly to food crops for control of slug and snail pests. Caffeine is a natural product which is approved as a food additive. Therefore, caffeine may prove useful for protecting food crops from slugs and snails."  This is from an abstract written by R.G. Hollingsworth, J.W. Armstrong, and E. Campbell and published in The Annals of Applied Biology, Volume 142, Number 1, 1 February 2003 , pp. 91-97(7).

Of course, you'd have to reapply it every time it rained, but I make coffee every day, and I can see myself sacrificing a cup to the sprayer and getting out there with it.  It would sure beat picking them off by hand.

This will give new meaning to the term 'slugging back a cup of coffee'.  I almost can't wait to try it.


Marianne said...

I put coffee grounds in the compost every day. Nice to know I'm detering slugs at the same time as feeding the soil.

Tamar@StarvingofftheLand said...

That is sheer genius. Here's my question, though -- if this was published in 2003, why haven't all the gardeners we know switched over? Surely, in all that time, somebody tried spraying coffee on their crops. If it had worked, wouldn't they have shouted it from the rooftops?

Since your growing season is ahead of mine, I trust you'll give this method a thorough test and, by the time I have slugs, I'll know just what to do. If this works, I'll buy YOU a beer!

Paula said...

Well, I think that a couple of things are at work here. Most folks who recommend coffee as a deterrent recommend coffee grounds sprinkled around the plants, which is a more hands off approach; you apply the grounds and you step back. The abstract recommends a 'drench treatment of 1-2% caffeine', which is definitely a more hands on approach. Aside from that, there's huge difference in how and where they're applied; one is grounds, on the grounds, the other is liquid, on the plants. So my thinking is that using coffee as a slug killer is kind of like Christianity: it's not that it doesn't work; it just hasn't been tried yet.

To really test this method, I need to find out what the percentage of caffeine there is in a given amount of coffee, say four or eight ounces (eight seems like such a huge sacrifice to me, but then, I'm writing this before seven o'clock in the morning). I will definitely do the research, and definitely try the method, because the slug population in these parts is really incredible, and supporting such a population takes a lot of food. My food.

Rae said...

Oooh! New remedy to try! Sweet!

I tried the beer thing after a friend gave us a case of skunky blue boar (skunky because he'd left the case in the back of his car all summer). It seemed to make the problem worse... Like advertising free booze to a bunch of college kids. Baaaaaad juju. Messy too.