Controlling slugs and snails (part 5)

May 27, 8:52 PMDetroit Organic Gardening ExaminerBill Canaday

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And THIS is what the enemy looks like

Natural Enemies

Snails and slugs have many natural enemies, including ground beetles, pathogens, snakes, toads, turtles, nematodes, and birds, but most are rarely effective enough to provide satisfactory control in the garden. An exception is the use of domesticated fowl—ducks, geese, or chickens—kept penned in infested areas. (Be careful, though, as these birds may also eat seedlings.) The predaceous decollate snail (Rumina decollata) has been released in southern California citrus orchards for control of the brown garden snail and is providing very effective biological control there. However, in light of the grief being given us by the ash borer and zebra mussels, why introduce another non-native species to Michigan?

Baits & Poisons

I only have personal experience with two sorts of snail poisons and, based on my research, I'm quite leery of all the others. The two I find acceptable are ferrous phosphate (Sluggo & Escar-go), which adds fertilizer in the form of iron and phosphorous to the garden and thus is a good choice early in the spring. Ferrous phosphate has the advantage of being safe for use around domestic animals, children, birds, fish, and other wildlife and is thus a good choice for a garden Integrated Pest Management (IPM) program. Ingestion of the iron phosphate bait, even in small amounts, will cause snails and slugs to cease feeding, although it may take several days for the snails to die. However, continued use would add too much phosphorous to the soil and change its pH, both to the detriment of the plants.

The other poison that I am comfortable with relies on timing to be effective and affordable but, done properly, the results are impressive to the gardener and devastating to the slugs. I wait for signs of slug activity such as slime trails and, that evening, I apply FRESH coffee grounds in a nearly solid layer over the soil surface. Slugs can't handle caffeine. Just sprinkle it over the ground densely enough that they cannot get to a plant without having to deal with the caffeine. It would appear that I get nearly 100% mortality because I rarely ever see another trail in the same growing season. Don't use this if you have toads in your garden … it's tough on their nervous systems too, and can prove fatal.

Here's what the University of California has to say about the others (you thought I was making this stuff up, didn't you :-)

“Baits containing the active ingredient metaldehyde are most common. Metaldehyde baits are particularly poisonous to dogs and cats, and the pelleted form is especially attractive to dogs. Metaldehyde snail baits should not be used where children and pets cannot be kept away from them. Some metaldehyde products are formulated with carbaryl, partly to increase the spectrum of pests controlled to include soil and debris-dwelling insects, spiders, and sowbugs. However, carbaryl is toxic to soil-inhabiting beneficials like ground beetles and earthworms and should be avoided if snail and slug management is all that is required.”

Take the hint … skip this stuff.

Water the garden in the afternoon before applying a bait to promote snail activity and apply the bait in the late afternoon or evening. Application on a warm, humid evening is ideal. Apply bait in a narrow strip around sprinklers, close to walls and fences or in other moist and protected locations, or scatter it along areas that snails and slugs cross to get from sheltered areas to the garden.

WARNING ON THE USE OF CHEMICALS