Garden Edition: a real slug fest: July
by Linda Coyner
This year's wet, cool spring followed by a damp start to summer has set the stage for a real slug fest, something you usually have to travel to the US Northwest to fully experience. Outwitting this gastropod in the garden is no easy matter if the multitude of old and new strategies that exist is witness.
The telltale sign of slugs and snails is ragged holes in foliage and stems stripped of leaves. (If the holes are neatly cut out, it's probably a caterpillar.) Fruit and vegetables -- especially tomatoes and strawberries -- are left with small, shallow holes in the surface that allow fungi and bacteria to enter and spoil the crop. If you have any doubts about the presence of a gastropod, just look for the trail of slime left on leaves, the soil, or paved areas of your garden. The trail might also appear on screen doors, garage doors and the side of the house, as happened to me in rural New York state.
Slugs and snails move about slowly on a single foot. The foot propels the slug through a river of secreted mucus. The trail serves another important purpose -- it leads fellow slugs to the host plant. The slime itself is a very sticky goo, that allows them to slither vertically or even on overhead surfaces. In fact, it takes vinegar to wash the goo off your hands. Slug slime also makes great glue, as some enterprising Canadian students recently discovered and won an award for their discovery.
The slime superhighway moves a slug about 2 1/3 feet a night, something I was particularly interested in since I'm prone to fling slugs into the grass and wonder how long it'll take for the slug to return. The answer: a couple nights. Mollusks work the night shift. While you sleep, they forage. It's possible to catch a glimpse of them at dusk or slithering back home before the dew dries in the morning. They also appear in the open on rainy, overcast days.
The slugs in your garden may be one of 40 or so species. Size varies from tiny (1/4 inch) to big enough to trip over (10 inches long), depending on the species. Most are less than one inch long and vary in color from cream to yellow to black; some species are covered with dark spots. By day the drying rays of the sun drive the creatures into hiding. They seek out cool, moist surroundings, and are adept at finding hiding places, even in sunny gardens.
Slug tactics take advantage of their habits, anatomy and preferences. Here's an overview:
Watering in the evening is akin to putting out a welcome mat, albeit a moist one. Adjust your watering schedule to avoid the evening. Water in the morning -- the surface soil will be dry by evening.
Snakes, toads, frogs, lizards, birds, geese, chickens, turtles, hens, moles, toads, hedgehogs, racoons, skunks, opossums are all on the gardeners' side in the battle against slugs. Tread lightly.
Create repulsive barriers
Rough surfaces tickle their bellies and the more irritating the substance, the better. Consider diatomaceous earth (see below), wood ash, crushed egg shells or sea shells, thorny twigs, pine needles, oak leaves, sandpaper, roofing shingles and hardware cloth. Changing the pH also tends to repel them but be careful not to sacrifice your plants in the process.
Try lime, watering with seaweed or using calcified seaweed meal, uncomposted manure (very acidic) or coffee grounds.
Diatomaceous earth (horticultural grade, not the type used in swimming-pool filters which has smoother edges and is far less effective) is the sharp, jagged skeletal remains of microscopic creatures. It lacerates soft-bodied pests like slugs, causing them to dehydrate. A powdery granular material reminiscent of powdered sugar, it can be sprinkled around garden beds or individual plants. It must be reapplied after a rain. Wear protective gear when applying, as it can irritate eyes and lungs.
Some gardeners take the herbal route, encircling their plants with pungent barriers. That might include aromatic plant material like mints, tansy, beebalm, ginger, garlic, mint, chives, basil, sage, rosemary and artemisia. Several web sites cited quack grass roots (we call it torpedo grass in Florida) and horsetail are additional effective barriers.