Snails and slugs are not typically pests of the greenhouse or growroom, although their presence in either is not totally unheard of. More so, they are frequent pests in outdoor growing areas; they are generalists as feeders and will eat almost any tender growth on food crops, ornamentals, trees and shrubs. They are particularly fond of seedlings and young plants.
Snail and slug populations tend to increase, or at least they make their appearance more widely known, after periods of rain and in moist areas. They are a long-lived gastropod, living for more than two years, so just because you may not see them right away, doesn’t mean they are not around. Control of the adults is the most effective approach. It is difficult to find snail and slug eggs since they lay them in the soil or under rocks or other debris where it is cool, dark and moist.
Damage from snails and slugs is relatively easy to identify—both chew large holes in the leaves of plants. They can also be found feeding on stems, fruits and bulbs as well. They leave a slimy trail in their wake, which can be useful in trying to track them down. Fortunately, there are dozens of ways snails and slugs can be deterred, lured or otherwise killed, all by using natural, organic or chemical-free methods.
Deterring snails and slugs is likely the first line of defense if you have had problems with these pests before. Natural deterrents such as mint or sage can be planted around your garden. They are great at deterring many pests that don’t care for the scent and have the added benefit of being harvestable. If you do not wish to plant these herbs, their leaves can be scattered around your plants and incorporated into the mulch.
Physical barriers can also be placed around your plants to deter snails and slugs. Many folks don’t know that when snails and slugs encounter copper, they get a slight electrical shock that causes them to retreat. It can be an expensive deterrent, but copper is available as a mesh and a foil. A band of at least three inches should be placed anywhere slugs and snails may cause damage, including tree trunks and decorative pots.
To ensure the continued effectiveness of copper, it needs to be periodically cleaned. Tarnished copper will not create the electrical current that repels snails and slugs. A less costly deterrent is coarse sand paper. It too can be placed in strips to deter snails and slugs from traveling across it.
Other coarse materials that deter slugs and snails include ground eggshells and diatomaceous earth, which is composed of ground-up fossils. Many gardeners use coffee grounds to deter snails and slugs. This method may work anecdotally, but there is little evidence to suggest that it is a sure-fire snail and slug control.
Luring snails and slugs away from desirable plants is another approach that can be performed as a stand-alone control or in concert with the deterrents. Lures can be created from items already in your garage or kitchen. Snails and slugs do not like to be in the sun and seek shelter during the day. Any flat object such as a board laid down on the ground in your garden can attract snails and slugs. More effective lures also contain the added benefit of food for the pests.
A potato slice, apple piece or even a citrus rind placed in the garden will likely attract one or more snails and slugs away from your plants. Large, flat, edible leaves such as lettuce or cabbage work great, too. This method is cheap but needs to be done daily until the snail or slug population is under control.
Hand-picking snails and slugs is a never-fail method of control. They will be more active in the cool of the morning and evening than during the day. Plucked snails and slugs can be put into a bucket containing a solution of wither salt water or insecticidal soap. Because of the mucous coating of the snails and slugs, it may be advisable to wear gloves, or use utensils such as tweezers or pliers to grab the snails and slugs.
If you raise chickens or other fowl, you can put the snails and slugs into an empty bucket and treat your birds to a slimy snack—they will love it. You can also set your fowl loose in the garden to control snails and slugs as well as other insects. This method should not be used when the plants are young as the fowl may be just as tempted to eat the tender foliage as any insects that are roaming about.
A homemade remedy of one part household ammonia to four parts water can also be used as an effective spray to control slugs and snails. The nitrogen in the ammonia supplies fertilizers as well. Another dual-purpose application is any product containing iron phosphate, which can be sprayed or spread around the soil at the base of plants. When it is consumed by snails and slugs, it causes them to stop eating immediately and kills them in two to four days. Any unconsumed product also supplies a dose of fertilizer to nearby plants.
Natural Predators & Pollinators
Whether it’s snails, slugs, spider mites, aphids or whiteflies, the best way to ensure there is a steady and varied population of beneficial insects that will consume the pests in your outdoor growing area is to plant a wide variety of flowering plants that bloom at various times of the year. These plants will provide shelter and a source of food for the beneficial insects you are trying to welcome to your growing space.
The actual plants chosen will depend primarily on where you live and what insects you are attempting to attract. Prior to planting any of the following plants, consult a local nursery professional to make sure they are hardy for your area. While not an exhaustive list, some of the more common plants that can be easily found in most areas around North America are:
Herbs: Coriander (cilantro), Dill, Fennel, Lemon Balm, Mint, Parsley, Thyme
Perennials/Annuals: Alyssum, Asters, Cinquefoil, Cosmos, Lavender, Lobelia, Marigolds, Penstemen, Sedum, Sunflowers, Veronica, Yarrow, Zinnias
Wildflowers: Dandelions, Goldenrod, Queen Anne’s Lace
Many of the same plants that attract beneficial insects into your yard can also serve as food sources for pollinating insects that will help increase your crop yields. Here is a list of tried and true plants for attracting pollinators to your garden:
Herbs: Borage, Catmint, Fennel, Lavender, Oregano
Perennials/ Annuals: Alstromeria, Alyssum, Asters, Bee Balm, Black-eyed Susan, Blanket flower, Butterfly Weed, Coneflower, Cosmos, Lantana (a shrub in warm climates), Marigold, Penstemen, Pincushion Flower, Red-hot Poker, Salvia, Sunflowers, Yarrow, Zinnia
Shrubs/Trees: Butterfly Bush, Lantana (an annual in cooler climates), Crabapples, Lion’s tail, Linden (basswood), Maples, Ninebark, Pussy willow, Serviceberry (Juneberry), Sumac, Viburnum
Regardless of where you live, it is always better for pollinators and the ecosystem if you plant native plant species. Native plants provide the food and shelter for animals and insects that are native to your area, and they are better acclimated for your area to withstand weather extremes. Introduced and exotic species are not. Native plants are deeper-rooted and are therefore able to tolerate periods of drought better than non-native plants.
Armed with the above plant list, it should be relatively easy to go into your local garden center or home improvement store and come out with a slew of locally appropriate, beneficial, pollinator-attracting plants. Selecting the right plant in the right spot will save you maintenance and money in the long run, with reduced costs associated with insect and disease problems.
If there is any doubt as to whether or not a plant is appropriate for your area or if a pest control method is harmful to beneficial insects or pollinators, you can always check in with the professionals at your local or county extension service. Remember, your plant choice is more than just an aesthetic one. It can and will reverberate throughout the entire ecosystem. Make it a good one!