The annual- no, perennial - battle against snails and slugs is under way. Sunset magazine recently did a survey that ranked snails and slugs as the worst, overall, garden pest in the Western states. Considering the competition with the likes of the field bindweed, strawberry root weevil, aphids and mildew, this honor is dubious. They may not be your worst pest but will still cause plenty of problems. Each spring numerous gardeners inquire as to why newly emerging seedlings and even transplants disappear overnight. The cause is usually these soft-bodied mollusks.
Slugs and snails are not insects but are more closely related to the shell fishes. They range in size from about 1/4 inch to several inches depending on the species. They are usually mottled, and color varies from whitish yellow to various shades of gray or black. Their rasping type mouth accounts for considerable damage done in a short time. They prefer seedling plants and maturing fruits and vegetables such as strawberries and tomatoes.Maturing fruits and vegetables are my favorite food, so I have no problem declaring war on these pests. Before you get started, realize your limitations. You will never get rid of the pests for good. You combat them and reduce their numbers for a season or two, but they will always come back - from your neighbor's lot, on new plants, from new soil, among other sources.
We have very few newly emerging seedlings at this time of year, and our harvest will slow down soon, so why worry about slugs and snails now? Unfortunately, they are prolific and are aided in reproductive endeavors by the fact they are not "hes" or "shes' but "its." Each slug or snail lays clusters of eggs right now and is capable of producing more than 300 offspring annually. Each one destroyed reduces the number feeding on the garden next year.
Slug and snail control is not a simple matter. The first plan of attack is altering the environment. Unfortunately most of the materials added to improve garden soil also improve the habitat for slugs and snails by creating moist soils with large amounts of organic matter. They generally breed in grass clumps, ground covers, lawns and other perennial plantings. They hide under rocks, boards and other dead plant materials. Reduce watering with cooler weather to reduce their hiding and egg laying habitat.
Slug and snail traps can be very effective. One excellent trap is a piece of lumber with some small strips nailed on one side. Place this in areas where plants are affected by the snails and slugs. Start the process by smashing one of the pests on the under side of the trap. Each morning go out and turn the trap over and dispose of the unwanted pests. They are easily dispatched by crushing. Look for and destroy the egg clusters that resemble clusters of small pearls. Salt will kill the pests quickly but is not recommended because it will damage plants.
If altering the environment and traps don't do the job, try burying some shallow pie pans in the garden so that the top lip of the pan is even with the soil line. Fill them with beer, yeast water or even plain water. The pests are attracted to the liquid and drown. Remove the carcasses frequently so new pests are attracted to the area.
In severe cases, bring out bigger ammunition. Many slug and snail baits are on the market, but they fall into two categories. The first are baits on almond, corn or other kinds of meal that are formed into pellets and scattered through the garden. Unfortunately, the exposed baits may attract pets, birds or other non-target animals. Avoid putting these non-target species at risk by using bait stations. The traps described earlier are effective, or use milk cartons with small doorways cut in the side. The bait is accessible but is protected from rain or irrigation and does not touch the soil. This helps limit the number of applications needed because the active ingredient is not washed away by frequent watering.
Make similar traps from small polyethylene containers such as cottage cheese cartons. Cut slots around the sides of the container. Bury the trap so the slots are level with the soil, and place the bait inside the containers. When pests are killed, remove, then renew the bait. Commercial baits are made even more attractive by moistening them slightly with apple or orange juice. Place baits in or around lawns, ground cover or other areas where slugs are known to hide.
Sevin as a spray is generally registered in non-crop areas and is effective against smaller slugs and snails. Since the pests are active at night, apply it in the evening. Another useful product containing concentrated metaldehyde attracts slugs and snails. It is sold as Deadline and is available at most nurseries. It has the consistency of gray toothpaste, and is effective when placed as a barrier between desirable plants and the hiding habitat.