GardenLine | Common Saskatchewan Pests | Slugs

Description:

Slugs are slimy, rather disgusting creatures that eat plants. Adults vary in colour from almost white to brown, grey and black. They are legless, elongate, mollusks (snails, shellfish, etc.) and prefer to feed at night. They will however feed during the day in moist shady locations. Their movement is highly dependant upon moisture availability. They move by sliding forward on a trail of secreted slime. The slime has a silvery appearance and is often used to detect an infestation.

The most common type of outdoor slug in our region is the grey garden slug, Deroceras reticulatus. All slugs are similar in general appearance but vary in colour and length. Slugs will feed on a variety of animal, green plant and fungal materials. Succulent fruit and tender leaves are their preferred hosts but slugs will also feed on root crops such as carrots and potatoes.

Slug eggs are very small (less than 3 mm or 1/8 inch in diameter). Eggs are colourless and deposited beneath the soil surface, making them very difficult to detect. Newly hatched slugs are also small and transparent making their presence easily overlooked. Because of this, slug eggs or young slugs can enter the garden on new plants or in soil materials. Transplants, perennial divisions, strawberry plants...etc, whether they are given to you by your neighbour or purchased at a retail outlet, can be responsible for infesting your garden. Even borrowed garden equipment can introduce slug eggs. Slugs, even though considered to be a slow mover, can move unaided from one garden to the next in an urban situation. Eggs, because of their size, can even be transferred on the bottom of footwear when crossing an infested area.

Slugs prefer warm, moist conditions. With the onset of cooler weather, slugs will become less active or even dormant, but with the return of moist warm weather, slugs soon assume their active state.

Control:

Control should begin as soon as slugs are detected. Slugs lay eggs in clusters of 200-300 eggs. Because of their capacity to reproduce in high numbers and the egg's ability to overwinter and withstand very harsh conditions even a small population can soon multiply.

There are many cultural or environmentally friendly means of slug control. Here are a few you may wish to try:

1. Inspect all incoming plants for eggs or adults and remove by hand.

2. Ensure adequate spacing between plants in the garden, stake tomatoes and use materials like chicken wire for peas to climb up to reduce the amount of foliage inclose proximity to ground level.

3. In the fall remove all leaf debris and clean up the garden area as best as possible.

4. Since slugs prefer moist, shady locations, laying out pieces of old lumber between the rows of your garden can help. Just go out in the morning, lift the boards and gather orsquish the slugs.

5. Beer placed in shallow containers was recommended in the past, but feeding beer toslugs can become quite expensive. It's the smell of yeast the slugs are attracted to,so we recommend a mixture of yeast, sugar and water, which should work just as well.

Dissolve 1 Tablespoon sugar in 2 litres of lukewarm water. Then add 1 teaspoon of yeast. Prepare this an hour or two before nightfall. Pour into containers and placethem out in the garden. Disposable plastic cups placed into holes and dug betweenthe garden rows work well when filled with this mixture. To enable the slug to crawlinto the container, the lip of the container should be flush with the soil surface. This way the slugs have easy access into the container but will find it hard to get out. Check the containers each morning to see if slugs have to be dumped out and thenplace out a fresh mixture in the evening.

6. Frequent tillage can physically destroy adult slugs and slug eggs. Rototilling in both the spring and fall can help reduce their population. In addition rototilling in betweenrows throughout the growing season will assist in control.

7. Abrasive materials like ground egg shells, oyster shells or diatomaceous earth can beplaced at the base of plants. As the slug ripples over the abrasive material theirbodies become lacerated causing the slugs to die from dehydration.

8. Wrapping cotton balls around the base of plants will prevent the slugs from climbing upthe stems as the cotton absorbs the slimy mucous on which slugs travel. Fibreglassinsulation may also be used in this manner.

9. If chemical controls are favoured. Visit your local supplier of gardening goods for various slug baits or slug tapes. The chemical in both baits and tape is Metaldehyde,which can be used close to plants, but not applied on plants.

REFERENCES:

Controlling slugs, by Grant Wood.

Slug Control in Gardens; Manitoba Agriculture; Pest Facts Agdex No. 625; May 1985.

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.