Slugs and members of the class Gastropoda propel themselves over most surfaces by contracting a foot muscle to move over a mucus/slime trail. They use teeth made of chitin to either eat their prey or to rasp holes in it. As they carry no shell, slugs can crawl through very narrow openings and will burrow into the ground to avoid cold weather and dessication. As they spend much time beneath the soil, slugs will sometimes feast on plant roots or tubers, causing an otherwise unexplained wilting of the plant leaves.
Most often though, slugs are noted above ground, snacking on leaves, stems, buds and fruit of brussels sprouts, artichokes, beans, peas, tomatoes, cereal crops, cabbage and citrus. Young seedlings are most at risk for slug damage and field trials have shown that the first 14 days post-emergence are the most critical.
Controlling Garden Slugs
Control methods for eliminiating slugs should vary with the crop, the physical site, the weather and soil type. However a combination of physical and biological controls coupled with slug-resistant plants should form the basis of an Integrated Pest Management approach to slug control.
Physical methods include using traps and various baits, erecting barriers of copper and scattering diatomaceous earth, lime or sand in slug-prone areas, to handpicking at night or in the early morning.
Biological controls range from predatory Decollate snails and Phasmarhabditis nematodes to predatory Staphylinid and Carabid beetles and Sciomyzid flies.
Also, certain horticultural practices such as planting trap crops of slug favorites like mustard and horseradish are helpful in reducing slug damages, in addition to avoiding the cultivation of a monoculture of prime slug food such as potatoes or cabbages.
Sanitation in the garden must be paramount to reduce slug infestations. Compost piles must be located far away from the garden and mulch, leaf debris, weeds and plant containers should be limited in slug-prone areas.