An infestation of slugs and snails can decimate a vegetable garden when humid and damp weather rolls in. To thwart these pests it takes a variety of techniques. Barriers and deterrents are your first line of defense.
Hard-leafed plants with strong scents such as rosemary, lavender and basil can be used as an aromatic wall that discourages slugs and snails from exploring further into your garden. Many varieties of flowers also deter slugs and snails, including geraniums, poppies, nasturtiums and fuchsia.
During the day slugs and snails will hide in cracks and under stones, boards, or anywhere that is dark, moist and humid. Remove such hiding places from your garden when possible. Wet boards can also be used as traps. In the morning, collect the slugs that are hiding beneath and drown them in a container of soapy water and toss them into the compost heap. Do not use salt on slugs and snails as it damages soil by increasing salinization.
Copper barriers around sensitive crops is effective, but can be expensive. Copper causes a small electric shock that deters slugs and snails. Copper tape 2-3 inches wide can be attached to the outside of the bed.
Sprinklers increase humidity across your garden and tend to help slug and snail populations blossom. Using drip irrigation or more targeted watering methods is advised, and will save water too.
In extreme cases, going into your garden at night with a flashlight and a pair of gloves to remove the pests by hand can be the best method, if done regularly until populations are under control.