Per request, I am writing about ways to remove slugs. In another blog I will discuss insect problems, also by request.
Spring time in the maritime Northwest is also slug time. Newly hatched slugs, tiny but ready to eat and adults that winter over under cover, perhaps underground if the winter is cold enough, feast on the new shoots of tender greens. Naturally, ideal garden conditions for spring bulbs and vegetables are the same as ideal conditions for slugs. How to minimize the impact of these slimy pests?
1) Remove places for them to hide; distance those places from tender plants that fall prey to the voracious appetite of the slugs. If you can not move planters or borders, copper strips, preferably about 3″ wide surrounding the planting area will deter the slugs. Staple this to vertical sides of planters, being sure there is no overhanging vegetation to provide an alternative route into the planter. Slugs will enter from the bottom of the tub as much as the top, so ensure there is a barrier to this as well. These destructive critters also lay eggs, small, pearly white balls, on the underside of available hiding places. Reduce tall grass and weedy patches as they also provide cover.
2) Physical removal is the surest way and least toxic method. You can bait them with citrus rinds and shortly after dark collect the gathered slugs into a screw top jar or seal-able plastic bag. By removing the population you reduce the number of adult slugs available to repopulate your garden.
3) Once you have removed the slugs in the evening, you can entice them with beer, the cheap stuff as they are not particular, placed at strategic intervals near plants they would usually consume. Using shallow, preferably covered, dishes 3/4″ above the soil surface to deter good-bugs like beetles from falling in, cut an entry hole, fill the shallow dish part way with beer. In the morning you can remove the slugs that drowned during the night.
4) Should you live in a rural area where slugs will migrate to your garden, or have neighbors less diligent than you, and the number of slugs doesn’t diminish with time, you might have to resort to more drastic measures. This decision should be seriously considered as the poisons available to kill slugs is also very harmful to pets, wandering animals, and small children. Read and follow all label directions to minimize negative results and actively reduce the number of slugs in your garden. Utilize covered containers with an entry hole cut in the side with bait inside. Place the containers lid-down on the soil surface in the evening. If the evening is dry you may want to dampen the soil where you are placing the poison to ensure the slugs will get to it; they tend to avoid dry soil.
There are some indigenous slugs (i.e. banana slugs) that are less destructive than their introduced cousins. Gray slugs, which are gray, brown, or tan-colored, originated in Europe. They are the primary culprits to focus on. Garter snakes and frogs as well as some birds, prey on slugs; if you have them, encourage them to aid you in your quest.
Good luck, I do not miss slugs. Here in the Columbia Basin we have smaller and fewer slugs as they prefer wet climates to our dry, high desert conditions.