SNAILS of COLORADO
Snails as Pests
The battle between gardener and snails is an ancient one tracing back to even medevial times and the bible. Ancient French marginalia, art done in the margins of hand copied manuscripts, frequently depict knights fighting snails. Why is this battle so heated and intense?
Similar to Humans
Knight v Snail II: Battle in the Margins (from the Gorleston Psalter, England (Suffolk), 1310-1324, Add MS 49622, f. 193v
One of the most interesting things people don't know about snails is that they have all the same organs and organ systems a human does. This means if you want to poison a snail it will probably kill/harm a human as well. In fact the FDA has not approved the common molluscicides bait traps for use on plants intended for human consumption. Even with ornamentals you run into the problem of other organisms or even pets getting into the traps and becoming ill (M. Flint, 2009). Hollingsworth et. al. (2009) tested the effectiveness of household chemicals in preventing snail damage to plants. Caffeine was found to be very lethal in even small amounts. Since a recent study of snails in Colorado has not been done, using lethal methods could literally be killing the last snail of its species, and hence leading to extiction.
Humane and Effective
Fortunately there are many other methods to try before resorting to lethal measures in your garden or potted plants. Like the saying goes "the best offense is a good defense" this holds true for the Super Bowl Champions Denver Broncos and snails in your garden. Tilling and preparing soil so as to prevent egg laying is the best way to clear your garden and pots of snails and slugs. In the spring before the rains start aerate and till soil and leave it loose and exposed to the elements. Snails need shallow, warm, and moist soil to lay eggs in. If you till, this will disrupt the microenvironment and lead to less slugs and snails come spring (M. Douglas, 2012).
Another form of defense is to build a snail proof barrier. This is most easily done on potted plants and planters. A strip of metal curved down will prevent snails from climbing into your pots. However, do not use copper as it can produce a lethal shock to the snail. Another way is to use a decorative medium that isn't pleasant to crawl on but not damaging, such as lava rock, other pourous rocks, or even fennel seeds. Diatamaceous earth is sold as a snail preventive but is not humane in that it cuts the snails soft body, it would be equivalent to us walking barefoot on razor blades.
There are common household products that can be used to prevent snail damage without harming the snail. Rosemary plants have long been used by gardeners to limit pests. Rosemary oil mixed with water and sprayed on plants prevents snails from chowing down by making the plant less palatable, meaning it tastes bad to them. The downside is that the solution would need applied every evening just as the snails are becoming active to be effective.
If all else fails there is the good old brute force method. Set up ideal spots for snails to hang low during the day, like a damp carboard box, leave the box over night and then in the morning you should have accumilated some snails that can then be relocated. This will require either walking or driving a bit to a suitable release site. If you throw them in your neighbors back yard they will just come crawling back, it may not be quicky but it will be inevitable. If a trap doesn't work then you can go out in the early moning or evening and hand pick the snails off your plants. Place them in a container and transport elsewhere. This same process can be accomplished using ducks. Ducks love to eat snails. In fact one vineyard in South Africa has exploited this characteristic to make entirely green, pestiside free wine. Avondale Vineyards takes a natural approach to wine making (http://www.avondalewine.co.za/naturesvineyard/predators/).