April is the cruelest month, if only because that’s when slugs and snails start to proliferate. Usually, in this column I seek out an expert to follow, but as far as these slimy underleaf denizens are concerned, I am an expert. After all, I live in Eugene, Oregon, where every year we crown our own SLUG Queen. True story. This year’s reigning queen is Jerril Nilson, aka Queen Slugasana. Over many Northwest seasons, I have tried all slug/snail strategies. We’ll start with eradication and then move to deterrents.
Killing Them Softly
I control adult populations with bait. However, I peruse the labels and don’t use metaldehyde, with or without carbaryle. The unintended consequences are too dire. Aside from killing earthworms and the birds who eat them, and who knows what else I almost lost my dog from a poison encounter. (She lived to a ripe old age, but was never again quite right in the head.) Consider only if you can completely control the environment, such as inside a greenhouse.
Iron phosphate (with cute names like Sluggo and Escar-Go) sprinkled around on a regular schedule won’t harm anything else. A less effective method is drowning slugs/snails in containers of beer or a sugar/yeast/water solution.
For direct encounters, try an ammonia spray. (One part ammonia to five parts water won’t hurt most plants, says Fred Davis, Hill Gardens of Maine.) I don’t go out on nightly flashlight forays to hand pick or cut the critters in half with scissors, but that might appeal to you.
Kill eggs in veggie beds by solarizing. Pin down plastic sheeting to raise the soil temperature several weeks before you put in your tasty (vulnerable) seedlings.
Make areas around plants unattractive to voracious mollusks. A thick sprinkling of wood ashes presents a pH the slimers dislike. To keep hostas in containers hole free, I twist dryer lint into fat ropes there’s always a new loop around the base of the plants.
For raised vegetable beds, I like a copper band of roof flashing nailed to the top board. Copper gives off a mild shock to slimy bodies. Copper bands are not as protective encircling individual plants because they get knocked about.
Look for plants unpalatable to mollusks. For instance, replace slug-shredded hostas with those that sport bigger beefier leaves, like Hosta ‘Sum and Substance’ or H. ‘Hadspen Blue’. Better yet, substitute the tougher foliage of lungwort, Pulmonaria ‘Raspberry Splash’ or P. ‘White Wings, Same hosta shape no slug/snail damage.