Snails and slugs can be very damaging
Snails and slugs can be very damaging to small transplants and their populations should be managed.
Although there’s no organic miracle cure for slug and snail problems, persistent efforts can limit their populations and reduce damage to a reasonable level. Below are a few methods we use! Combining several of these approaches may help you and your garden stay one step ahead of the molluscan menace.
REDUCE HIDING PLACES
Snails and slugs rest during the day in shady, damp places, then emerge at night to feed. A thorough garden clean-up to minimize potential habitat is a first step in cutting down their populations. Debris in contact with the ground, such as boards, bricks, unused flower pots, weeds, and other daytime hiding places should be removed from the garden.
Consider thinning ivy, irises, agapanthus, lilies, ice plant and other succulents and ground covers to increase sunlight and airflow, making the habitat warmer, drier, and less attractive as shelter. Weed the area around tree trunks and keep grass near the garden area trimmed.
Not all hiding places can be eliminated. Low ledges on fences, areas around water meters, the space between the boards and the soil in raised beds, and other likely habitats should all be checked for snails and slugs. When hunting in stands of iris and other plants, be aware that snails react to vibration and will drop into the base of the foliage. Slug are more difficult to find in the daytime since they often worm their way into the soil via crevices left by plant roots or earthworms and stay hidden until after dark.
Any snails and slugs you collect should be crushed and buried or composted, or thrown in the trash. If you’re squeamish about squashing them, drop your prey into a bucket of soapy water. Do not use salt to kill your catch, since it is toxic to plants and very hard to get out of the soil once it is in there.
Be on the lookout for snail and slug during your hunts or while gardening. According to UC Berkley plant pathologist Robert Raabe, “snails dig holes about an inch deep and deposit their opaque white eggs in them. Check any individual snail on the ground during the daytime.
It… probably is laying eggs. Dig out the eggs and allow them to dry out.”
Pest control experts William and Helga Olkowski note, “young snails remain in the nest for several days, then stay close to the area in which they hatched for a number of months. This is important in management since a large number of young snails in one area is a clue to where the snails are laying eggs. “Slugs lay clear eggs about the size of bb’s – look for them attached to boards and other smooth surfaces.
Once you’ve identified potential hiding places, be consistent about cleaning them out. “Continue to search snail hiding places, daily if possible, until your catch becomes noticeably smaller, “writes Pam Peirce in Golden Gate Gardening. “Then continue hunts of their favorite hiding places once a week. Don’t stop handpicking; keep it as part of your ongoing control program even if you use other methods as well. It’s your most effective weapon. “Combine daytime hunts with night-time searches, when slugs and snails come out to feed – but be aware that for every slug you catch, there are likely 20 more still hiding.
CREATE TRAPS AND BARRIERS
After the garden is cleaned up, traps can be used to concentrate slugs and snails in a few spots so that they’ll be easy to find and remove. Traps should duplicate desirable habitat, i.e, they should create dark, moist conditions for daytime hiding places. Plastic or unglazed clay flowerpots placed upside down on uneven ground in shady spots, or boards raised slightly off the ground with runners can be used to trap snails. Inverted grapefruit rinds, boards or black plastic laid directly on the ground will lure slugs. Moistening the ground underneath will help draw your prey. Check and empty the traps every day or two; crushed or drowned prey left at the trap will attract more victims.
Gardeners report mixed success with beer-baited traps, which are more effective for slugs than snails. Apparently, it’s the smell of yeast that attracts the mollusks, so if you don’t want to share your six-pack, try making your own bait: mix 2 tablespoons of flour, 1 teaspoon of sugar and ½ teaspoon of baker’s yeast in 2 cups of warm water. Set your homemade brew or storebought beer (go for the yeastier brands) in a shallow saucer or lid, with the rim of the container at ground level. Traps can also be made from plastic containers. It may take quite a few traps to make a dent in a large population of slugs.
Barriers of wood ash, diatomaceous earth, or cinder placed around garden beds can all inhibit slug and snail travel. The band of materials should be at least 1 inch high and 3 inches wide. Be aware that ashes and diatomaceous earth don’t work once they get wet.
Copper flashing and screen provide a more permanent barrier. A rim of copper to form a flange can be nailed to the edge of a wooden raised bed. Apparently, the slime that snails and slugs excrete produces a shock when it contacts the copper, prompting the pests to make a u-turn.
Copper screening can also be used to fence off an area. It should be buried in the ground at least four inches deep with two inches protruding above the soil. Note that these barriers will also trap snails and slugs inside the area you want to be protected, so keep up the handpicking efforts in the beds. If you use copper barriers, make sure to clear away any overhanging plants or other materials that could provide a bridge into the garden.
On-farm, we make fun of controlling the slug and snail populations by going out after a rain and seeing how many we can find. Be sure not to dispose of the San Diego native snails which are beneficial to the garden. They are easy to distinguish from the European snail.