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Slimy Slugs

University of Minnesota Extension, Stearns County News
June 17, 2015

Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns, Benton & Morrison Counties


Slimy Slugs
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (06/17/15) —Have you ever discovered that something in the night had eaten holes through your hosta leaves or even in your vegetable or strawberry garden?  One probable source of this damage is slugs. Hungry slugs can be quite destructive in our gardens, therefore being both proactive and reactive is important in controlling the slugs and the damage they cause.

Slugs are slimy, soft-bodied animals, often described as shell-less snails.  Slugs prefer cool, moist areas, and often feed at night and hide during the heat of the day.  Slugs feed on both live and decaying plant matter. 

Slug damage consists of large, ragged holes in the leaves to near complete defoliation of young plants. Slugs are present from spring to fall, and activity only decreases naturally during drought conditions.

Managing slugs can be a challenge.  The first step is to remove mulch and leaf litter near plants. It is important to do this in early spring to remove any slug eggs that may be present.  If you maintain wood mulch for weed prevention, keep only three inches near the plants themselves.  The second tip is to water your gardens in the morning so the plants and the area around them has a chance to dry out during the day before the slugs come out to feed at night since slugs prefer a moist environment.  In addition, thin, stake, or prune lower leaves to encourage better air circulation to help keep soil surfaces more dry.

Trapping is also an option; there are several methods of trapping. One trapping method is to put down a board, shingle, or damp newspaper in the garden where the damage is occurring.  The following morning, lift up the trap and physically squish all slugs that are present.  This can be repeated night after night until the slug damage is no longer present. 

Another trap attempted over the years is using a container of beer; set the container into the ground so the top is even with the soil level, fill to one inch below the top of the container with beer or a water-yeast mixture of one teaspoon yeast to three ounces of water. The slugs are attracted to the smell and fall into the liquid and drown.  Filling the container to one inch below the top forces the slug to reach for the liquid, ultimately losing traction and falling in.  However, effectiveness is really related to the design.  In some studies it appears poorly designed or executed traps resulted in very little mortality to slugs.

Planting an alternative to hostas might also be a viable option.  Plants that perform well in shade but appear to be less desired by slugs are: astilbe, dicentra, lobelia, and vinca. Plants for areas with partial shade are phlox, campunula, and hemerocallis.

If other efforts do not seem to be effective, there are products on the market as well. Products containing iron phosphate such as Sluggo, or Escar-Go, or product with metaldehyde such as Deadline or Defender, or a product with copper compounds.  Products vary from granules applied to the surrounding soil to a liquid which is sprayed on the plants. Always read and follow the insecticide’s label.

Before slugs make our plants look ragged, or eat our beautiful red strawberries before we have a chance to pick them, make efforts to control these slimy little critters.  For more information on slugs visit http://www.extension.umn.edu/garden/insects/find/slugs/
 

Contacts

Beth Berlin
Extension Educator, Horticulture
(320) 255-6169
adam0062@umn.edu
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