Flour and Yeast Slug Traps: Start Next Year's Pest Control Now!

The leaves are changing colours and the vegetable garden is powering down, but for garden slugs, life is starting to get exciting. After hiding out through summer’s hot, dry weather, slugs emerge in autumn to feed, mate and lay eggs for a month or more.

Trapping slugs in the autumn reduces the number of eggs deposited near crevices of your raised beds, as well as the number of adults that overwinter in garden debris or among your hostas. There is a short-term benefit as well, because trapping will reduce the number of slugs chewing holes in your last crops of leafy greens.

Not that you want to rid your yard of every slug or snail. These and other little molluscs help break down organic matter, and they are a are a major food source for birds, frogs, and other wildlife. Some slug species cause little damage to plants, but the grey garden slug or milky slug (Deroceras reticulatum) is a persistent pest in most gardens. Garden slugs chew holes in spinach and strawberries, mow down tender seedlings, and end up as unwanted bits of protein in heads of broccoli.

Slugs have few fans among gardeners, though we do create lovely habitats for them, and then get mad because they show up. An organic garden decked out with beds, benches, containers and compost is a slug paradise. Framed beds and raised planters are especially hospitable to overwintering slugs because they provide shelter and a few degrees of warmth on cold days. They are prime sites for trapping slugs in autumn.

Trapping Slugs with Beer

For many years, gardeners have used shallow containers baited with beer as slug traps. They do work, though some slugs figure out how to survive brief swims in beer and return to the garden, refreshed and renewed. The type of beer is unimportant, though yeasty lagers may have a slight edge. For maximum effectiveness, beer traps must be emptied and replaced every couple of days, depending on the weather. Slugs feed and court mostly at night and on mild, rainy days.

Flour and Yeast Slug Traps

Not everyone keeps beer around the house, but most of us have a bit of flour. In search of cheap, easily made slug attractants, Rory McDonnell and other researchers in Oregon compared beer, strawberries, cucumbers, and other natural baits, and the clear winner was a slurry made from flour, water and yeast. In other words, bread dough slug traps. As the yeast chows down on the flour, gases are released that slugs find irresistible.

The recipe for the bread dough lure is a simple mix of two cups (470ml) water, one cup (235ml) flour, and one packet yeast. This mixture is heavy on yeast and water compared to real bread dough, because it is designed to slowly ferment. The mixture should be thinner than pancake batter, so the slugs will fall in.

You can use any container that is deep enough to hold the foamy mixture and can be outfitted with entry holes for slugs and buried halfway in the garden. It should also have a lid to keep out rain. I like to use plastic food tubs with little doors cut in the sides to make bread dough slug traps. Once a week, I dump the contents in the compost and start over.

Bread dough slug traps can be left in the garden longer than beer traps, and they work best when situated where they can stay put for at least four days. In field experiments in Oregon, Montana and Hawaii, the highest number of slugs were captured three days after the bread dough traps were set out, when the bait had started to go sour.

Get Ahead With Flour and Yeast Slug Traps

In my garden, the autumn slug trapping season lasts about a month. Trapping slugs in autumn during the last weeks before the weather turns cold reduces the breeding population, which means fewer eggs will hatch in spring and fewer adults will survive winter. One advantage to slug traps is that you can target areas of your garden where you had slug problems this year, or where you plan to grow slug-prone lettuce, cabbage or beans next spring. Don’t miss this seasonal opportunity to thin the ranks of your garden slugs!

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