Snails and Slugs
Slow as they may seem, a “cornucopia” of slugs or a “rout” of snails can quickly consume your garden. Especially in wet weather, these slimy visitors seem to appear out of nowhere, and they’re hungry.
But did you know that some snail species are beneficial? In Florida, only a few species of snails and slugs actually damage living plants. Others live on fungi or decaying plant material, or are predatory and feed on other snails. These predatory snails are beneficial, helping us keep the true pests in check.
Biology
If your garden is plagued by snails and slugs, you know that they behave differently than other garden pests. This is because snails and slugs are mollusks, not insects. They are relatives of conch, oysters, clams, and scallops.
Most slugs and snails are omnivores, feeding on fungi, decomposing plants, and soil. Some feed on healthy plants, however, and these are the species that make pests of themselves in your garden. It’s unusual to catch them eating though; snails and slugs feed primarily at night. Lacking waterproof skin, they dry out quickly and prefer humid, wet environments. Because they do not have shells, slugs in particular must conserve moisture at all costs.
Identification
Damage from snail and slug pests appears as oblong, irregular holes at both the margin and the center of leaves and flowers. Thicker leaves may have damage on only one side. Oftentimes you’ll see trails of mucous around these damaged sites.
Being nocturnal, these pests aren’t always feeding when you’re scouting. Slugs and snails don’t usually go far though — if they are indeed the culprits you’ll find them under pots, mulch, and leaf litter nearby.
For the most part, snails and slugs prefer natural, undisturbed areas. Only a few species are likely to be garden pests. And there are garden-friendly snails, too. Predatory snails, like the rosy wolf snail (Euglandina rosea), feed on other snails and slugs.
(synonym Achatina fulica). Credit: Lyle, J. Buss, UF/IFAS
To avoid killing the snails that help manage other garden pests, we encourage all gardeners to identify snails and slugs before attempting any control methods. Snap a picture and email it to your county Extension office. We’ll be happy to help you ID the mollusk in question.
Another reason to have your slugs and snails identified is to help scientists track and eliminate invasive species. Slugs and snails reproduce by laying eggs but most adults are hermaphroditic. This means they are both male and female, making invasive species more difficult to eradicate. Even if you take no other action, sending in a photo to be identified can be very helpful to the work of Florida’s scientists and Extension agents.
Pest Management
Integrated pest management, or IPM, is a comprehensive approach to managing plant pests. IPM uses many different methods to cause the least harm to people, property, and the environment. While there are chemicals available to manage snail and slug populations, we suggest beginning with cultural and mechanical management.
Cultural Practices — Snails and slugs require very moist environments. Reducing irrigation can make your garden less appealing. Removing excess leaf litter, mulch, wood, and stones from the base of your plants will also help. If these habitats can’t be removed, you can scout regularly and keep populations down mechanically. Encouraging biological control, by welcoming the predators that eat garden snails, is another cultural option. Identify your snails before you reach for a chemical control to avoid eliminating beneficial species like the rosy wolf snail.
Mechanical Practices — Slugs and snails can be trapped and removed easily. If you provide a shady, moist environment (like a piece of cardboard laid on the ground) they will hide underneath as the day warms up. Later in the day you can lift the cardboard and remove or kill them by hand. Another popular trap involves sinking a steep-sided vessel, like a cup, into the soil to about ground level. Fill the cup with beer or another bait. Slugs and snails will enter and remain trapped.
Diatomaceous earth and egg shells are reported to kill slugs and snails, too, but we have no research to support this claim. The logic is that these abrasive materials damage the pests’ soft undersides as they cross them. Another common barrier is copper, but in Florida it oxidizes quickly and becomes inactive.
Chemical Controls — Most people know salt is toxic to snails and slugs. Unfortunately, salting your garden will damage your plants. Apply enough salt and you can ruin your soil, too. Hydrated lime and sulfur dust can also deter slugs and snails but, again, they will also change the composition of your soil.
The pesticides that control snails and slugs are called “molluscicides.” These are commonly baits, which are a combination of a food to attract the snails and slugs that is mixed with a chemical substance that is lethal to them. Any molluscicide must be registered with the Environmental Protection Agency (EPA) and will contain a label with explicit instructions for use. Remember: the label is the law. To be used effectively and without unreasonable risk of harm to people or the environment these products must always be used according to the label.
For more information on snails, slugs, and pest management, contact your county Extension office.