Just when you thought that it was safe to go into the garden again or at least let your plants fend for themselves, you find it isn't true.
I mentioned these plant destroyers in a column a month ago, but judging from the number of questions I have received, they seem to still be wreaking havoc. Read on to find out why you need to continue your battle right now.
The European brown snail was introduced to California in the 1850s as gourmet food. Someone forgot to eat enough of them, and they made their way to Utah via imported nursery stock or food. Their cousins, the slugs, are basically the same creature without the spiral shells. They are so slow their name is part of the description of a "snail's pace" ... That describes their speed of movement not their voracious appetites and they damage more plants than most other garden pests.
These pests are often lumped with insects, but they are mollusks and are closely related to mussels and clams. They move by gliding along on a long, flat, muscular organ called a foot. To make their travel easier they secrete mucus or slime which dries to form a silvery slime trail.
During our wet, cold, spring, these pests proliferated beyond belief. Every pot I turned over had them stuck to the underside and they would chew off small seedlings as fast as they poked out of the soil.
The heat and the dry weather always slow them down, so why write about them now? The answer is, they are reproduction machines run amok. The adult brown snails lay about 80 spherical, pearly white eggs at a time into holes in the soil. Unlike many other garden pests that die over the winter, these come back next year with even bigger appetites.
Slugs mature in three to six months, depending on the species, and lay groups of three to 40 clear, round eggs under leaves, moist soil and other protected areas. Both snails and slugs are hermaphroditic, so there are no males or females all of them lay eggs. To make more of these nefarious scoundrels, they lay groups of eggs up to six times a year.
Defeating them takes a multipronged strategy. Unfortunately, ground beetles, snakes, toads, turtles, birds and other natural enemies don't fully control them. Domesticated ducks, geese or chickens control them, but they often eat young plants and also leave behind droppings.
Slugs and snails need moisture to thrive but survive dry conditions by hiding in protected areas. Your first battle is to get rid of their hiding places. They love dense groundcovers including ivy and vinca, dense shrubbery, mulch, rocks, boards or anywhere else they can be out of the sun and stay moist. Plant your vegetables and favorite flowers away from where the pests congregate.
Focus on plant selection. The pests love cabbage, beans, lettuce and most vegetable seedlings. Strawberries, melons, dahlias, delphiniums, marigolds and hostas are also on their gourmet menu. Resistant plants include California poppy, pelargoniums (geraniums), impatiens, lantana, nasturtiums and scented foliage plants including lavender, rosemary and sage.
While it is never a favorite task, hunting the pests is highly effective. After you water, go out with a flashlight and collect them. Drop them in a plastic bag or a bucket containing soapy or ammonia water. Don't use salt as it is harmful to your soil. Never crush and leave them because eggs in their bodies continue to develop and hatch into more pests.
Trapping is another way to collect the pests. Set out boards in moist areas to collect them. Put old melon rinds upside down to attract them. Beer traps are overrated as they have to be changed out frequently and also must have deep, vertical sides to keep the creatures from crawling out again. It is the fermented material that attracts them, so yeast in a little sugar water is equally effective.
Copper barriers are effective, but the price of copper might be prohibitive. The copper is thought to react with the slimy secretion made by the pest and causes an electrical current to deter them. The copper sheeting must be at least 2 inches wide to be effective.
Snail and slug baits are often the first choice of many gardeners but must be combined with other cultural controls to be effective. Most bait contains metaldehyde, an irritant that causes the pests to lose moisture. It is not a direct poison, but it stimulates mucous production to detoxify the bait.
This overstimulation of the mucous production can kill the pests, or if they are caught outside if it is hot or dry, they die from desiccation. If they can get to moisture, they usually recover. Avoid watering for several days after baiting to increase the effectiveness of the bait.
Use all baits as directed on the label. If you do not follow the directions, you increase the hazards and reduce the control. Pellets or other rain-safe formulations last longer and are not as attractive to nontarget creatures. Deadline is highly effective if used correctly. Iron phosphate baits including Sluggo and Escar-Go are safer products to use around pets and wildlife.Your declaration of war does not include cease-fires, truces and, of course, no surrenders. Get your neighbors to also declare war or you may not win because of the never-ending supply from their property. While they are not clever adversaries, they are extremely persistent. Never give up because each creature left alive now is capable of producing more than 300 offspring by next spring. That alone is reason enough to renew your efforts against these garden destroyers.
Larry A. Sagers is a horticulture specialist at the Utah State University Extension at Thanksgiving Point.