Toronto
Master Gardener Factsheet 
Toronto Master Gardeners are trained volunteers dedicated to providing horticultural information to the public.
For answers to horticultural questions contact the Toronto Master Gardeners' Info Line at the Toronto Botanical Garden (416) 397-1345 (Mon. to Fri. 10 a.m. to 1 p.m and Sat., Sun. and Holidays noon to 3 p.m.) or our web site.
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Toronto Botanical Garden is a volunteer-based, charitable organization whose purpose is to inspire passion, respect and understanding of gardening, horticulture, the natural landscape and a healthy environment.
777 Lawrence Avenue East
Toronto, ON M3C 1P2
Tel. 416-397-1340
Fax. 416-397-1354
www.torontobotanicalgarden.ca
Slugs and Snails
Slugs and snails are mollusks (Class Mollusca). Both have soft, slimy elongated bodies. Slugs are very similar in form to snails. The primary difference is that snails have a spiraled protective shell. Slugs vary in colour from yellow-brown to deep gray in colour and vary in size from less than half an inch to 4 inches in length. Both snails and slugs have two retractable antennae.
Their chewing leaves irregular holes and gnawed edges on foliage. Sometimes only the main veins remain.
Often one can observe a silvery, slimy, mucus trail or excrement that is left behind.
They can cause widespread injury and even the death of some plants by eating the leaves, flower parts, vegetables, fruit, or by tunneling into bulbs, tubers or roots. Take action as soon as you observe plant damage.
Many ornamentals such as daffodil, gladiola, hosta, iris, larkspur, strawberry, sweet pea and tulip are targeted as well as vegetables (lettuce, Chinese cabbage) and wild plants (dandelion).
Both slugs and snails overwinter (as eggs or adults) by burying themselves in soil and plant litter.
Snails can live for a several years, laying eggs each spring. The length of the live cycle is dependant on the species. Slugs, however, complete their life cycle in one season mating in late summer and laying eggs in fall that are left in decaying organic matter usually in damp, dark conditions.
Slugs and snails are mostly night feeders that can cause serious damage, especially in damp, shady areas and in wet weather.
In very hot, dry weather they cease feeding activity.
The City of Toronto adopted a new municipal by-law (spring 2004) that restricts the use of pesticides. For details about the by-law visit the Pesticide by-law page on Toronto Public Health's Web site at www.city.toronto.on.ca/pesticides or www.toronto.ca/health. Questions may be e-mailed to pesticide@toronto.ca.
A combination of methods may have to be used to control damage from slugs or snails.
Nematodes: One natural control is a nematode, delivered in vermiculite, that is used to control lawn pests (Steinernema feltiae). This cold tolerant product, or Hortscan, has to be spread for slugs and snails, rather than applied in a water-based spray.
Natural Predators: Natural predators should be encouraged into the garden by creating habitats for them. Birds, large beetles, frogs, toads and garter snakes all dine on slugs and snails. These predators all require water and shelter such as a small shallow pond, some rocks and or a dry stone wall. Turning over soil regularly, especially around pest infested areas helps to expose slugs and snails, and their eggs, to these predators.
| Barriers (2"-4" wide) sprinkled around plants: | Pea gravel, powdered ginger, horticultural sulphur, diatomaceous earth, crushed hot chili peppers, crushed limestone or eggshells, pine needles, lime, coarse sand, wood ashes, wood shavings, human or horse hair (chopped finely), oak leaves, bark or seaweed mulch (first rinsed with fresh water), or cocoa bean mulch. Don't spread material too thinly. Diatomadceous earth and cocoa bean mulch should be reapplied regularly as they soften and lose their effectiveness. Remember that some substances will change the pH level of the soil (e.g. do not apply lime near acid loving Rhododendron). Do not use straw or sawdust as mulch. Choose bitter-tasting plants such as oak leaves or artemisia to deter these pests. |
| Hand-picking: | Use gloves because the slime does not come
off easily. A pin or toothpick can also be used. Handpicking these pests
for five to ten minutes daily, in the early morning or evening, over a
two-week period, should decrease the breeding population. Slugs can be
disposed of in soapy water. The outer leaves of lettuce can be left around the garden to attract slugs and snails. They can be collected in the evening and disposed of. |
| Direct Application: | Apply the following directly to slugs and snails: Lime; a 50/50 solution of vinegar and water; fresh lime juice; table salt. |
| Liquid traps: | Bury a small, open container in the ground, with the top level with the ground. Possible containers are aluminum pie pans, pet food cans, or tuna cans. If you can find a way to cover the container without hampering entry for the slugs, that's even better. Possible liquid bait for the container includes beer (most effective in the first 24 hours), or the following home brew: mix 1 lb. of brown sugar with 1/2 package of dry yeast in a gallon jug; fill with warm water. Ferment for one or two days, uncovered. |
| Metal strips/mesh: | Copper strips are worthwhile barriers for
containers and should be applied around the rims. From a very thin sheet of copper, cut 2" strips and fasten them around the outside of raised beds, about 1" down from the top of the beds. Copper gives a mild shock to slugs. Aluminum screen mesh can be fashioned into a "fence" with garden stakes used to keep it in place. Take a 5"-wide strip of mesh and unweave the top two horizontal strands of wire form the top edge. Bend the exposed vertical strands to face away form the plants. Push the bottom edge of the strip and garden stakes about 1" into the soil around the plants. |
It is important to control all pests and diseases with good cultural practices such as improving soil fertility and aeration, keeping soil well mulched to enhance soil moisture levels, watering during periods of drought, feeding plants during periods of growth and by weed removal. These practices will ensure optimum plant health and growth.
Slugs seek out moist dark places during the day and are mostly active at night and at temperatures below 70-75°F. If you mulch, try to wait until the average temperature is above 70-75°F before applying.
Avoid overwatering the soil and foliage, especially in the evening. Promote good drainage by raising borders and amend heavy soil to lighten it.
Slugs and snails love rotting vegetation, so if you compost, use barriers to prevent them from getting into the bin. Remove general debris from your garden because debris can shelter slugs and snails.
Gardeners can choose plants that are slug and snail-resistant. These pests love plants that are soft and juicy but there are those with built-in defenses. Plants that are repellant to the pests include those with hairy surfaces such as Lambs' Ears (Stachys byzantina) or the Lungworts (Pulmonarias), silver plants which usually have a rough leaf and stem covering, plants with long tough fibres such as ornamental grasses and bamboos, plants that exude sap such as Euphorbias (Spurges) and Rue, strongly aromatic plants such as hardy geraniums, yarrows (Achillea), catmints (nepeta spp.)as well as Anthemis and pelargoniums, plants with spiky leaves such as ornamental thistles, and plants with tough, leathery surfaces that originate from arrid areas of the world such as Sedum spectabile, Lily of the Nile (Agapanthus), phlox, penstemons and Osteopermums. There are even many hostas that are not slug and snail friendly. These tend to be the larger, blue varieties with tough felted and puckered leaves such as Hosta sieboldiana 'Elegans'. A word of caution! These plants are resistant when mature but are still vulnerable when young.
Factsheets are produced by the Toronto Master Gardeners in association with the Toronto Botanical Garden. They provide introductory information about a broad range of horticultural topics and are intended for personal use and study purposes. Should your gardening group or organization wish to use multiple copies we ask that you inform the Toronto Botanical Garden at info@torontobotanicalgarden.ca.
Date revised: January 8, 2006
