I saw an earthworm the other day, so it’s a fair bet that slugs can’t be far behind. This damp weather is perfect for them, so if you see plant leaves full of irregular holes and looking as if they’d been shot with birdshot, the chances are good that you have slugs.
The best way to prevent slugs is to keep the garden clean and free of leaves, logs, stones and other debris that slugs use for cover. Keep mulch pulled back away from the base of plants, keep shrub branches up off the soil surface and keep grass and weeds at the edge of gardens mowed. Slugs lay their eggs in the soil and regular cultivation exposes them. The eggs look like masses of small, clear, jelly like pearls and once exposed can be squashed with the back of a hoe or your foot. Slugs like damp places, so don’t water in the evening. A fine, smooth, dry soil surface free of hiding crevices will discourage them.
If you’ve done all of this and still have slugs, try putting down pieces of board, shingle, damp carpeting, wet newspaper, or any other material that will lie flat on the soil surface and not blow away. Slugs feed at night and like moist, dark places to hide during the day. If you check the underside of which ever material you choose each morning by flipping it over, you should see slugs clinging to it. They can then be scraped off the surface into a container and discarded, or squashed. This should be done each morning for about a week, with boards or other materials spaced every few feet throughout garden beds. If yours is a vegetable garden, just run boards down the rows. One of the most effective ways to kill slugs and their eggs is to freeze them.
There are many other methods of slug control, but I think the above method is the easiest. I’ve used rings of wood ashes around plants and they work well, but the ashes have to be replaced every time it rains. I’ve also used many saucers of beer and have never caught a single slug. For those of you who want saucers of beer in your garden; in 1987, Colorado State University Entomology Professor Whitney Cranshaw had his students conduct a test for the beverage most favored by local slugs. Kingsbury Malt Beverage was determined the slug favorite, with Michelob and Budweiser coming in second and third. Slugs really love the yeast and barley in beer and will travel great distances to get it, so if too much is used in the garden, you may actually be attracting them.