Create a pine-needle mulch Dried out pine needles are like sharp little slug daggers, and will stab the slugs who try to pass over them. Collect the pine needles from the trees in your yard after they fall, or visit a local gardening center to pick some up. Spread these in a thick blanket around your plants to keep out the slugs. Keep in mind that pine needles are highly acidic, so you may have to mix some lime into the soil to balance it out. How to Get Rid of Garden Slugs