Our sidewalks and patios sparkle with the shiny, silvery mucous trails of snails and slugs in the early autumn mornings. Snails and slugs hibernate during hot and dry summer weather (as well as in winter), but reappear in fall when humidity is higher and temperatures are moderate. The fall batch of snails and slugs is feasting on the tender new growth of fall seedlings and transplants, loading up on calories before they lay their eggs which will mature in spring.
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It’s impossible to kill all the snails and slugs in your garden, since a single baiting kills only about 60 percent of the population, but using a combination of eradication methods on a very consistent schedule can greatly reduce their populations and damage.
Handpicking snails (even the toughest gardeners get squeamish about handpicking slugs) takes a lot of effort at first, but within two to three weeks the snail damage will be greatly diminished.
Irrigate your garden in late afternoon to wet the soil, then go out at dusk with a flashlight to follow the snail trails back to their hiding places or their favorite feeding areas. Snails and slugs are creatures of habit and can usually be found at the same spots. Check under old boards, along fence rails and the sides of the house, under low-hanging branches and in dense foliage (guara, agapanthus) or ground covers such as ivy for their hiding spots. Clean out weed patches and remove hiding places when possible.
You can use the “big foot” method to crush them or drop them into a bucket of soapy water. You can also place them in a plastic bag in the trash, but they often escape the bag. Do this every night for a week, then two or three times the next couple of weeks, then once a week until cold weather arrives.
Copper barriers work by creating a sort of shock when the snail and slug mucous touches the copper. Barriers made of copper foil can be attached to the edges of raised beds or wrapped around tree trunks (especially young citrus trees) with good repellent effect.
Snail baits are the most convenient method of knocking down snail and slug populations. Two types are available; those formulated with metaldehyde (some Corry’s products including Deadline) and those formulated with iron phosphate as the active ingredients (Escar-go, Sluggo).
Metaldehyde baits are toxic to dogs and cats and can make children sick; the pellet baits made with cereals or with apple pectin are especially attractive to dogs. Corry’s Deadline bait also contains carbaryl which is toxic to earthworms as well as beneficial insects. If applying metaldehyde baits, use one with 4 percent metaldehyde rather than 2 percent; the 4 percent formulation is more effective. Don’t apply metaldehyde baits to edible plants.
Iron phosphate baits are considered relatively non-toxic and safer to use around pets and children.
When applying baits, spread them around your vulnerable plants and near their hiding places. Don’t make piles. Reapply bait after irrigating or rainfall; the baits lose effectiveness when damp.
Send Elinor Teague plant questions at firstname.lastname@example.org.