Slugs.

There are several species of slugs, which are mollusks, in Pennsylvania.

Some are small. Others can reach up to eight-inches-long.

Slugs overwinter as eggs, immature or mature slugs in protected areas in fields, vegetable gardens and flower gardens. They also can be found under boards, plastic or decaying vegetation.

Slugs are especially troublesome in gardens with lots of crop residue. Slugs become active in spring and continue their life cycle. A mature slug can lay up to 80 spherical, pearly-white eggs at a time, up to six times in one year.

Slugs damage plants by chewing holes in leaves and fruit. They leave silvery mucous trails where they travel, which is certainly unappetizing on herbs and lettuce.

Once slugs have moved into a crop it is just about impossible to wash them all off, which can significantly decrease your yield.

It is best to try to prevent the slug population from moving into your vegetable garden or flower beds than try to get rid of them once they are established.

It is critical to start early because after the populations builds it is really difficult to stop them.

Slugs do provide some ecological benefits. They are a food source for many animals and they break down organic matter, which is important for recycling nutrients, such as nitrogen, through the food chain. And they eat dead organic matter.

Here are tips for controlling slugs.

Sanitation:

Remove overwintering sites and resting areas prior to planting. This includes loose boards, plant residue and stones.

Traps:

Set out boards or damp burlap bags in the evening. Slugs are mostly nocturnal and they will hide under the traps. In the morning, you can destroy them.

Natural enemies:

Encourage toads, garter snakes and ground beetles. They can be helpful but are not reliable to completely control slugs.

Hand-picking:

If you go outside in the evening you will probably see slugs emerging from their daytime hiding place to feast on your plants. You can then pick them up with a gloved hand or tool and put them in soapy water to kill them.

Diatomaceous earth:

This comes from fossilized mineral deposits of the silica-containing cell walls or “shells” of once living aquatic algae called diatoms. The mineral, diatomite, is mined in open pits. Chunks of the mineral are pulverized into a flour-like powder. The diatom fragments have sharp microscopic glass-like edges that abrade the outer water-protecting cuticle of the slug, causing it to lose water and further dries out pests by absorbing protective fats and oils. It can discourage slug populations under dry conditions but must be reapplied if it gets moist.

Iron phosphate:

This is sold as a granular product. It acts as a stomach poison in slugs and snails by damaging their digestive tissue. Several formulations are allowed by the Organics Materials Review Institute.

Pesticides:

Pesticides to kill slugs should only be used as a last resort. If you do choose to use pesticides, follow the directions on the label.

Spotted Lanternfly Update: The Circle Trap is a new trap for homeowners that is a nonchemical alternative to sticky tape. For information on the spotted lanternfly and directions on how to make your own circle trap or where to buy one, go to: https://extension.psu.edu/spotted-lanternfly.

“Growing Green” is contributed by Lehigh County Extension Office Staff and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613.