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Slugging It Out in Your Garden

Four battle plans for saving your plants

By Nancy Cain
Published: June 1, 2006
WELLESLEY ISLAND, N.Y. – Eighteen garden slugs were killed in the early hours of Saturday morning in the most devastating attack on gastropod forces in almost nine months. It was the second assault this week in the cottage front yard. On Monday the gardener had stormed the 55-foot flower bed, abducting six slugs, after a messy battle with slime that left many daisies fighting for life and one dead young plant.
– Gastropod Network News

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Photo by Tony Colter
And so went the Slug War in the early days of summer 2003. It was the last time I had the upper hand.
   
Today the daisies are all gone, the flowerbed is lined with thick ribbon grass (who needs color, anyway?), and a few hardy hostas serve as both sentinels beside the front steps and all-night slug diners. When it comes to the dark, soggy flower bed under my cottage roof’s drip line, the slugs, just like us, have a great view of the water.
   
It all began when I planted 10 daisy plants chock full of buds. All went well until the buds began opening. Within a day, I didn’t have daisies – I had the ugliest stalks of yellow flower middles you could imagine.
   
Alarmed, I asked my neighbor, Virge (whose vibrant gardens had guilted me into tackling this flower bed in the first place), to take a look. In a nanosecond, she noted my daisies were shrink-wrapped with slime and diagnosed my problem: slugs. Over the summer, I educated myself, fought a war of attrition, yet lost every single daisy.
   
Here is my debriefing in the hopes it will help you in your battle:

Enemy reconnaissance.  The most important thing I learned is that slugs need dark, damp conditions to survive. The best long-term control involves creating drier conditions. But short of creating a cactus garden, knowing how slugs eat, move and prosper is what you need to confront the enemy.
   
Slugs feed mainly at night, grabbing tender leaves with their guillotine-like jaws. After rasping away the surface of a leaf, slugs chew the material underneath, creating the characteristic Swiss cheese effect.
   
Slugs particularly like daisies, delphinium, hosta, lettuce, strawberries and most young vegetables. In general, slugs avoid plants with stiff leaves and highly scented foliage like lavender, rosemary and sage.
   
Another telltale sign of slugs is a slime trail, a secretion of hydrophilic or water-attracting mucus. Mucus is the lifeblood of the slug. It is an aid for locomotion, a trail for navigation, a barrier to water loss and a unique form of self defense. When attacked, a slug releases a thick, self-defense slime that can seal the mouths of predators such as snakes and shrews and can make some animals, such as ducks and dogs, gag.
   
If there is soil, there are probably slug eggs in it. They can remain dormant for years, hatching when the conditions are right. In colder parts of the country, slugs mate during the warm months and overwinter in egg form. Depending upon the species, slugs may produce as many as 500 jelly-like eggs in a lifetime. For every one slug you slay in the fall, you knock off potentially hundreds of new sluglets in the spring.
   
Slugs have natural enemies, including ground beetles, snakes, toads, frogs, lizards, salamanders, lightning bug larvae and turtles, but slugs always seem to prosper. The only truly effective predators are domestic fowl: ducks, geese and chickens. If only I could get those pesky Canada geese and slugs together!

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Photo by Tomasz Resiak, istockphoto.com
Battle plans. Basically, there are four ways to manage the enemy:  Search-and-Destroy, Trench War, Fence Building and Nuking them.
   
The Search-and-Destroy method involves providing a dark, damp cover for slugs: over-turned flower pots, damp boards, inverted melon or grapefruit rinds, wet carpet squares or rolled up, wet newspaper. Early in the morning, the cover is flipped over and the enemy is picked off one-by-one using either rubber gloves or chop sticks. One poor woman using this method reported collecting as many as 700 slugs in a single day. Yuck!
   
With the Trench War method, your mission is to capitalize on your enemy’s weakness for fermenting materials in order to trap and drown them. Dig a trench and in it place margarine tubs full of any noxious, fermenting material you can think of: beer, yeast and water, sugar water, grape juice, etc. Yep, the beer drowns them in platoons.
   
Some gardeners have successfully built tiny Barrier Fences around each plant, made of everything from dryer lint to egg shells, baking soda, salt, lime, sand paper, copper flashing, diatomaceous earth – anything to irritate the enemy.
   
Nuking pests with commercially available baits should be the last resort. Metaldehyde (e.g., Deadline or Slug-It) is the most commonly used chemical, which irritates the slug, causing it to die of dehydration. However, it has to be used with utmost caution since it is also toxic to other animals, including earthworms, your dog and even your child. A less toxic alternative is iron phosphate (e.g., Sluggo or Escar-Go!), which is a naturally occurring fertilizer found in soil.
   
Whatever offensive you choose, you have to know one thing: Slugs are couch potatoes. Not only are they sluggish, but they barely move one foot an evening. It’s best to lay your bait and traps where slugs hide during the day – in dark ground covers and under rocks. No point attracting the enemy to the plants you’re trying to defend!

   
Final report. Like many other gardeners, I fought a war of attrition. I must admit I had more enjoyable things to do on my summer mornings than manage beer traps and pick slugs out of my flowerbeds with chopsticks. Unless I intend to invest in serious landscaping to remove the conditions that led to the slug insurgency, I’d better get used to that ribbon grass.

Frequent contributor Nancy Cain has a doctorate in animal behavior. She never dreamed she’d use her degree to devise battle plans for slug wars.

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