Tooele Transcript Bulletin – News in Tooele, Utah
image Garden slugs, along with snails, are among the most notorious garden villains, according to gardeners.

August 1, 2013
Award for worst garden pests goes to slugs and snails

We live in a world of contests. The top ten people in the class. The richest people in the world. The blue ribbon prize winner at the fair. The straight A student.

There is another kind of contest for things that are the best at being the worst. The most notorious criminals. The worst bullies. The dirtiest jobs.

Slugs and snails are rated by many gardeners as the worst garden pests. To be named the worst is a dubious honor considering the competition of other devastating pests like Mormon Crickets, grasshoppers, army worms and more.

But the designation of the worst probably should go to slugs and snails. The others mentioned are cyclical so although they can wreck havoc with crops, but they don’t do it every year. But slugs and snails are ever with us.

These pests are not insects but are mollusks that are closely related to shellfish, such as mussels and clams. While snails are not literally slugs with shells, they are very much alike biologically.

Both glide with a long, flat, muscular organ called a foot. Mucus, or slime secreted by the foot aids in locomotion and dries to form a shiny white silvery trail. You may find these serpentine trails on sidewalks after rain or on soil surfaces.

They owe their continuing presence in part to the wide variety of their diets. They feed on living plants, fungi and decaying plant materials. They are particularly damaging to seedlings and maturing vegetables or fruits that touch the soil. It is annoying to pick a juicy-looking ripe tomato only to find a large hole eaten into one side by slugs or snails!

You don’t see these pests too much on sunshiny days. They are active at night or on dark, cloudy days. If you search during the day, you will find them hiding from the sun under plants, rocks, wood, or compost piles. They need moisture to thrive, but they will survive even in our hundred-degree days by hiding out in protected areas.

Another aspect of their ongoing presence is that they are hermaphroditic — there are no males or females. All are capable of reproducing.

They lay several clusters of eggs — primarily in the fall. The clusters look like a mass of moist, white pearls about 1/8 inch in diameter. Depending on the species, there are 20 to 80 eggs in each cluster.

Controlling them is always wise, but fall pest control is most important because they lay most of the eggs then. Although the pests cause less damage to plants in the fall aggressive control measures prevent large numbers the following spring. Each pest could lay up to 300 eggs so each pest eliminated could reduce the possible offspring for next year by 300.

Control Measures

These pests are difficult to control, so focus on reducing their numbers and their damage to valuable plants. The difficulty is that cultural practices that promote good plant growth and help maintain soil moisture create the perfect habitat for slugs and snails.

Organic matter retains soil moisture and keeps the pests protected. It may also provide food for them. Water management is critical to control these pests. The problem is always more serious when moisture conditions are high.

Stretch irrigation intervals as far apart as possible. Besides saving water, this is another reason to water deeply and infrequently. Avoid watering in protected hiding areas if there are no plants there. Do not over-water when using chemical baits. The water dilutes the bait and makes it ineffective.

Sanitation

Clean up potential hiding places in the garden. Remove boards, stones, and any debris that shelters the pests. Remove weeds or unnecessary foliage so the soil surface dries out rapidly. Dense groundcovers and turf are ideal hiding places. Choose areas away from these protective hiding places for vegetable, and flower gardens.

Search and destroy is a time consuming but effective method of controlling slugs and snails if it is done regularly. Daily removal is recommended. In early morning or late evening, search through hiding places and look for these pests. Put them into a container of salt water or a plastic bag that you can tie off and destroy.  Do not rely on mashing them in the garden because the eggs remain in the carcass. They then hatch even though the parent is dead.

After initially reducing the population, handpicking can be cut to once a week.

Barriers

Although there is a common believe that slugs and snails avoid rough, irritating barriers, experiments show that is not particularly effective. Mesh copper screens eight inches wide are an effective barrier. They do not like to climb over the copper, so it keeps them out of small, selected areas and prevents damage to valuable plants. Barriers are non lethal and divert the pests to other nearby vegetation.

Natural Enemies

Natural enemies, including chickens, geese, ducks, and other birds, seek out and destroy slugs and snails. The birds may also damage young seedlings and they leave droppings that may not be appealing. Some ground beetles, rove beetles, and certain flies are natural enemies of snails, as are toads and snakes.

The predacious decollate snail is often promoted as an effective biological control. It is not recommended for garden situations, since decollate snails may feed on seedlings, small plants, and flowers once other snails are controlled.

Traps

Traps work well to control the pests. One inch strips of lumber nailed on two sides of a 12”x12” board make an excellent trap. The pests crawl underneath it each day. Start by crushing one of the pests on the bottom of the board as bait to lure others. Go out each day, turn the trap over, and destroy the pests.

Bait traps using beer, yeast water, or even plain water also attract slugs. Use a cottage cheese carton or similar container with the edges buried at ground level so the pests crawl in and drown or cut holes in the sides near the top and bury it to the level of the holes. Put a lid on top to keep rain water or sprinklers from diluting the contents.

Fill reservoir with beer or yeast water. The slugs and snails are attracted to this, enter the liquid and drown. Remove the carcasses to maintain the appeal of the trap.

Covered, deeper containers are more effective than shallow pans of liquid. The greater depth prevents pests from escaping. Remove and dispose of the pests each morning.

Chemical Bait

If natural controls are not effective, consider using, chemical baits to increase the effectiveness of control programs. Baits are only effective until they become wet. For best results use baits in small shelters or traps. Before using any bait, always read and follow all label directions and keep away from pets and children.

Metaldehyde has been the standard bait used for many years and is most effective in dry, warm weather. It doesn’t kill the pest directly but it paralyzes them and causes them to froth and lose large amounts of water. During warm weather or on dry days, the pests die of desiccation. It is less effective in rainy weather or in cool areas because the pests recover a few days after eating the bait. Avoid scattering baits under dense plants where there is no sunlight as this diminishes control.

Metaldehyde baits can be used around food plants as long as the edible parts of the plant do not contact the bait.

Metaldehyde and Sevin or (carabyl) are sometimes combined as baits. Sevin increases the effectiveness against cutworms, sowbugs, earwigs and other insect pests. Use baits in groundcovers, hedge rows, and other shady, moist areas where slugs and snails hide.

Metaldehyde is the active ingredient in all slug and snail baits. Because there are no other chemical controls, continuous use of this product results in resistant populations. For this reason, use baits only when necessary and as part of an integrated pest management program that emphasizes other control measures.

Exposed baits may be attractive to pets, birds or other non-target animals. Slugs and snails are attracted to baits from several feet away. Bait stations in strategic spots are efficient and effective. This limits their availability and they last longer than those exposed to rain or sun.

The simplest bait station is a board trap covering small piles of bait. . The area remains somewhat moist so slugs and snails tend to congregate under these. Milk cartons with “doorways” may be placed on their sides. Placing baits in the traps keeps the baits accessible but protected from rain or irrigation and from touching the soil. Convert cans or plastic food containers with tight, fitting lids to more elaborate bait stations. They make it more difficult for non-target species to access the bait.

These are two ideas for making traps or stations. Cut a 1/2-1 inch slot on two sides of a carton. The cartons may be painted to blend in with the garden surroundings. Bury the trap so the slots are level with the soil.

Make a 1/2 inch to 3/4 inch hole near the center of the lid. Bury the container so the soil is at the lid level. Combine these containers with baits to lure the slugs and snails to their final meal.

Commercial baits are even more attractive when moistened slightly with apple or orange juice. Check the traps frequently and remove dead pests and replenish the bait as needed.

Use bait stations anywhere pests are active. The can or carton keeps the baits from contacting the soil or plants. Choose locations around the garden perimeter to intercept pests migrating from lawns, groundcover or other favorable habitats. When they establish a foothold in the garden, place the stations where they are active.

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