Slugs thrive in a moist environment, which our climate provides for nine months of the year and our watering habits typically maintain for the remaining three. Western Oregon has about 10 species of slugs that are considered horticultural pests, only one of which is native (the banana slug). The tiger slug is one of the most common species seen in our Portland gardens.
Pros and Cons: From the gardener’s perspective, there isn’t much good to say about these voracious terrestrial mollusks except that they eat and recycle plant matter, and serve as a food source for some birds and beetles. The trouble is that pest slugs will devour just about anything in your garden. So if you want your veggies to make it to your plate, be proactive. The major exception to this rule is our homeboy, the banana slug, which lives in wooded areas and rarely bothers garden plants. When taking up arms, go easy on this unfortunate soul.
Battle Plan: Deter slugs with paths and mulches composed of rough gravel or hazelnut shells—slugs don’t like to cross sharp or hot surfaces. Wide copper strips surrounding planters or raised beds also create a mild electric shock when slugs touch them, but they must be kept untarnished. If deterrents don’t work, try search-and-destroy tactics: At night, when slugs are feeding, hunt them down and snip them with scissors or drop them into a bucket of soapy water. Or try a commercial iron phosphate product such as Sluggo to bait the slugs and cause them to stop feeding. It’s safe to use around animals and pets, and the material breaks down into a soil amendment that plants can use.
The best time to catch or bait slugs is in September or October, before they lay eggs, followed by March to June, when they are most active and plants are most tender.