A snail on hosta leaves which have been previously damaged by snail / slug attack.See also:
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How To Use WD-40 To Keep Slugs & Snails Out Of Your Plant Pots
Slugs and snails like to make irregular holes and chewed edges on the leaves of your plants, but WD-40 can help keep them away from
your potted plants.
Known for being most active during damp or humid conditions, slugs and snails typically try to find shelter after it rains.
Once it is drizzling or raining, go outside and spray your pots with WD-40 to make them too slick for the pests to climb.
The best place to spray is right in the middle of the pot. You want the barrier ring of WD-40 to be at least three to four inches wide so the slug can't cross.
Be sure not to spray the plant as it can burn the leaves, causing more damage than the slugs and snails would, or the soil, as you don't want the plant to digest the chemicals.