Slug it Out with Slugs
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Slug it Out with Slugs
Allison Kosto
MSU Broadwater County Extension Agent
Recently, I headed to the garden to harvest potatoes for dinner. I peeled back the black fabric mulch and was greeted by a magnitude of slimy little creatures… Ugh. Slugs. While they didn’t appear to be causing any damage to my potatoes, I’ve spotted them throughout the garden and their presence is alarming. What can be done about these pesky creatures?
Slugs are land-dwelling mollusks. They are more similar to snails, clams and mussels than other garden pests like insects. They are soft-bodied and slimy without any legs. They have two pairs of feelers on their head. They can be difficult to spot in the garden because they primarily feed during the night. However, you may be able to see their signature slimy trail. During the day, they seek shelter in soil cracks and underneath plants and debris. In my case, they were enjoying the shade and extra moisture provided by the mulch.
Slugs overwinter in the soil, burrowing up to six feet deep. They lay their eggs in soil cracks or under debris. Eggs hatch in the spring or early summer. They feed on both living plants and decomposing plant material. They have rasping file-like mouth parts that leave irregular holes in plants. They can also feed directly on fruits and vegetables. In addition to feeding damage, the wounds create the opportunity for fungi and bacteria to enter.
One of the best ways to deter slugs is to create an environment that doesn’t appeal to them. They need moisture to survive, so practices that decrease moisture will reduce slug problems. The use of drip irrigation and soaker hoses helps reduce moisture. If you water overhead, do it earlier in the morning to allow time for the garden to dry. Remove any potential shelter for slugs such as surface debris and mulch. Increasing air movement around plants is also helpful. Methods to do this include the use of trellises and increased spacing between plants and rows. You can also select plants that are resistant to slugs.
Baits have been shown to be an effective means to destroy slugs. Slugs are attracted to fermenting materials. Traps can be created using beer, yeast water or sugar-water to trap and drown slugs. Traps should be at or below the soil surface to be most effective. Traps only have a range of a few feet and should be replaced frequently. Traps can also be created from boards or moistened newspapers. Check daily and kill any slugs.
The use of repellents and barriers is another common method. Because of their soft bodies, slugs avoid traveling over acid, alkali or abrasive materials. Diatomaceous earth can be an effective deterrent. Certain metals including copper are toxic to slugs, so using copper foil can deter slugs around raised beds or greenhouses. Copper products such as copper sulfate can also be used as a pesticide.
For chemical control, slugs are not susceptible to insecticides so molluscicides should be used. The most common product is metaldehyde. It is sold as a granular bait (i.e. Bug-Geta) or a paste or gel (i.e. Deadline). Metaldehyde works by dehydrating slugs. However, slugs can recover if moisture levels are high. It is safe to use around flowers and ornamental plants but is not labeled to use near fruits and vegetables. Additionally, dogs are attracted to metaldehyde which can be toxic to them.
Another chemical option is iron phosphate. Trade names include Sluggo and Slug Magic. Research has shown it has similar effectiveness to metaldehyde and is not toxic to dogs. They can also be used around edible crops. Ammonia sprays can also be used but must be applied directly to slugs. While salt is toxic to slugs, it should not be used around plants as a method of control. Excess salt can be damaging to plants.
For assistance identifying garden pests or control recommendations, contact MSU Extension in Broadwater County at 406-266-9242 or allison.kosto@montana.edu. As for the slugs in my garden, I haven’t started slugging yet. My use of mulch for weed control will make this difficult and, for now, their damage is minimal. I may just cringe when I see them and attempt to live in harmony.
