Ugh Slugs!!
They're everywhere! Slugs are a problem in gardens almost everywhere that there is shade, moisture and plants. If you are not familiar with these creatures, you can think of them as snails without shells. Slugs are actually mollusks and are not even related to insects. While there are many types of slugs around our area, we are lucky to only host some of the smaller varieties. We could be as unfortunate as those folks out in Eugene, Oregon, known as the Slug Capital of the World, where it isn't uncommon to come across slugs that are 6 inches long and bright yellow.
Slug Biology 101
Understanding a little about slugs and how they live can help you deal with them in the garden. Slugs have very soft, exposed bodies, and exude a slime that they then slide across. Slugs will bother a wide range of plants, but they have their favorites. Unfortunately for those of us in Minnesota who love hosta, slugs do too. They go after them like they're slug candy. Since slugs have soft, exposed bodies, they prefer cool, moist areas. They avoid sun because they may dry out, so they feed largely at night when it is cooler and more moist. To understand how slugs multiply so quickly, it helps to know that they are hermaphrodites, creatures that have both male and female body parts. That means that even when there aren't enough slugs around for much dating and mating, they can manage it all by themselves. Slugs lay eggs that look like clumps of tiny gelatinous pearls, each about the size of a pin head. The eggs are deposited in the soil where they may hatch in a few weeks or lay dormant for months until there is enough moisture. Slugs take about a year to mature and overwinter in the soil. Their natural predators are toads, snakes, birds, turtles, ducks and even chickens!
Identifying Slug Damage in Gardens
The most obvious sign, of course, would be to find the creatures. Unfortunately, that's not as easy as it sounds. Because of their soft bodies, slugs tend to hide during the day when you might be out in the garden. Slugs do their work at night. Taking a flashlight out at night to look for slugs is one way to check for them. An easier way to find slugs is to look for their damage or trap them. There are several ways to identify slugs so you can see how much of a problem you have.
Most gardeners don't know they have slugs until they see the damage. Slugs are rasping creatures and damage plants by scraping layers off leaves, flowers or any other soft tissue. Their presence is usually easy to confirm because they leave a shiny trail wherever they have traveled. On many plants, especially those with larger thick leaves, slug damage is distinctive because they make irregular holes with smooth edges. The holes are usually larger than a pencil eraser and smaller than a quarter. The damage also tends to be within the leaf blade instead of along the edges. Most other chewing insects will eat from an edge and take much larger areas. Severe damage on a hosta will leave the leaves looking like swiss cheese. On some plants, they seem to go for the nice, tender new growth. That is common on impatiens and marigolds. Another slug favorite is ripening fruit–especially soft fruits that are close to the ground, like strawberries and tomatoes.
Options for Dealing With Slugs
There are several ways to deal with slugs in the garden. These include a variety of ways to create inhospitable environments, such as trapping or poisoning the slugs and creating barriers. Sometimes it will take a combination of methods to establish control. Research is currently being done to test a type of nematode that seems promising against slugs. There are actually lots of folk remedies floating around in gardening books and magazines that may work, too. Always use caution. Some recommendations (such as tilling the soil several times) will actually do more harm than good. If you have a strong stomach you can always pick off the slugs and dispose of them. Early morning is best.
Here are some details on the most effective and popular methods of controlling slugs:
Creating an Inhospitable Environment
• Think sun. Slugs avoid any place sunny.
• Encourage toads and snakes to visit your garden.
• Keep the surfaces surrounding your plants rough and dry.
• Clean up any plant residue and other places slugs may hide during the day.
• Grow varieties of hosta that are more "slug resistant," like those with puckered or thick blue leaves.
• Avoid composting slug infested plant material.
Trapping
• Create a slug pit by inserting a tuna can into the ground where you suspect a slug problem. Make sure the edge of the can is level with the ground, and fill it with about an inch of non-poisonous liquid bait. Slugs are drawn to yeasty smelling liquids, such as beer. An inexpensive alternative to beer is to make combine a quart of warm water, a packet of dry yeast and a little sugar, molasses, or honey. Give the mixture 15 minutes at room temperature to activate the yeast. Keep it in the refrigerator, and use it later to rebait the traps. Once attracted to the traps, the slugs fall in and drown. Traps should be checked every day or two, emptied and the bait refreshed.
• Slugs are hide during the day in the nearest cool, dark place. Lay down a shingle, smoother side down, where you suspect slugs. Pick it up the next day and scrape them off the bottom of the shingle. Another option is a section of wet newspaper, still folded. When you pick it up the next day, you can simply throw it away, slugs and all, and put down a new section the next night. Overturned flowerpots or saucers work as well.
Barriers
• Diatomaceous earth (DE) can be spread around an area or a plant to deter slugs from reaching it. DE works because it is actually flat, sharp edged crystals that shred the slugs' soft undersides, causing them to dry out. DE does have to be renewed after a rain.
• Put down a layer of sharp sand. It stays in place and stays effective. Unfortunately, this option isn't very attractive.
• Copper strips are available in some garden centers and by mail order. Slugs will not cross copper. This is one method that works even after it has rained.
Baits/Poisons
• There are two basic types of bait: One type is made with iron phosphate (Slugoä), and is safe and effective when used as directed. Although it may seem more expensive, you use a lot less of it in the long run, making it an affordable alternative. Another form of slug bait has been around for years and contains the chemical metaldehyde. This bait comes in pellets, powders and a gel. Metaldehyde-based baits have several serious drawbacks. They need to be reapplied frequently and may also poison some of the natural predators of slugs, such as toads, snakes and birds. Pets and small children may be attracted to the poison pellets, too, Use them carefully as a last resort. Follow all directions and cautions.
©Bachman's 2007
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