Garden Tips: How to combat those slimy garden invaders

What is the difference between slugs and snails?

The obvious difference is that snails have an external spiral-shaped shell and slugs do not. Both are mollusks and belong to the class of animals called gastropods. Both have soft bodies and move along using a large muscle called a “foot.” To aid in locomotion, these muscles secrete slimy, slippery mucous, leaving a silvery trail behind. Slugs and snails also use their mucous to maintain body moisture, defend themselves, and aid in reproduction.

While it is very easy to identify slugs and snails, it is not always easy to detect their presence in the garden or landscape. If you miss their slime trail or pretzel-shaped fecal pellets, the first clue to their presence is the appearance of irregular holes of various sizes in plant leaves. Slugs and snails eat plant tissues by using their rasp-like tongues to scrape off plant tissues, leaving behind holes with smooth edges. Slugs and snails feed on a wide variety of green plants, as well as on fungi and decomposing plant material.

Much to the dismay of gardeners, slugs and snails are indiscriminate eaters when it comes to green plants. However, they do seem to favor certain plants, especially those with very soft plant tissues that are close to the ground. They are notorious for devouring young new seedling plants and feeding on mature strawberries and tomatoes that touch the soil. Some of their other favorites include hosta, daylilies, dahlias, marigolds, basil, lettuce, cabbage, peas, beans, potatoes and squash.

Because slugs and snails feed primarily after dark when it is cooler, you are unlikely to find them noshing on your plants during the day. Instead, they will be hiding under rocks, leaves and plant litter waiting for darkness. If you suspect that these critters are causing damage to your plants, look for them after the sun goes down.

First, water your garden late in the day to encourage their activity. Then go out after dark with a flashlight to look for them on the damaged plants. If you find any, use gloved hands to place them in a bucket of soapy water or a sealable plastic bag. If they are simply crushed and left in the garden, the eggs in their bodies may still hatch. Doing this nightly hand-picking (and then weekly after their numbers drop) can significantly reduce your mollusk population.

Not excited about hand-picking? Try trapping. There are all sorts of ways to trap slugs, such as sinking plastic cups or other straight-sided containers into the ground so that their top edge is at soil level. The trap is then filled part way with beer or a mixture of water, sugar and yeast. The slugs are attracted to the yeasty liquid, crawl in, and drown when they can not crawl out. Traps should be cleaned out and renewed every couple of days. To be effective, you will need numerous traps because only slugs and snails within a few feet of the trap will be attracted to it.

There are also a number of commercial slug baits on the market that can be used to attract and poison slugs. However, some are very toxic and need to be applied strictly according to label directions to keep children and pets safe. Newer baits, such as Sluggo and Escar-Go, that contain iron phosphate are much safer. When slugs and snails eat even small amounts of iron phosphate bait, they stop eating and die within several days. In addition to being safer, some research indicates that iron phosphate baits are more effective than other types, especially after rain or irrigation in the garden. In using any bait, it is important to read the label and follow the directions.

So if you see holes in plant leaves or fruit close to ground, do not assume it is an insect doing the damage. It may be slugs or snails. Go out after dark and look for these slimy midnight garden marauders. Yuk!

This story was originally published June 2, 2018 at 5:45 AM with the headline "Garden Tips: How to combat those slimy garden invaders."