Slugs will ruin a vegetable garden pretty fast unless some serious means of taking care of them is implemented. The electric fence has proven to be pretty well 100% effective in my experiments to date. The fence consists of two runs of wires spaced about 3/4 inch apart running around the perimeter of the raised bed - one wire is connected to the +ve terminal and the other to the -ve terminal of a battery. An electric current will flow through the slug if it makes contact with both wires at the same time. The resulting "shock" with usually cause the slug to turn back.
I've been using a 9-volt battery as the power source, the battery lasts the whole growing season but the voltage drops to 5 volts or so by the end of the season (my measurements). It's a good idea to check the volage once in a while to make sure the battery is still providing enough voltage (corrosion can be a problem at the battery connectors). A few years ago when setting up a new fence I didn't have a 9-volt battery connector so I used a multi-battery AA holder that I had on hand. The combined series connection of batteries gave 12 volts. This turned out to be a bad idea as the 12 volts would more often than not kill the slugs rather than just turn them away.
The nice thing about the slug fence is that it is on duty 24-7, many other slug control methods require some kind of regular checking or resupplying. Also, no dangerous chemicals to worry about with this setup.
My first electric fence was mounted on a low "raised" bed garden. It was effective until the vegetation in the garden grew high enough to bend over and touch the ground - this gave the slugs the bridge they needed to reach the main feast.
The video below demonstrates how a slug typically reacts when attempting to cross the fence. It is interesting to notice from the video that once the slug was "shocked" a number of times (by making contact with both wires) it was then conditioned to react the same way when touching just one wire (no current flow possible through the slug).
Step 1: The Video Demonstrates the Effectiveness of the Fence
Step 2: Prepare the Raised Bed Soil and Frame for Planting and Wiring
- remove old growth and weeds from the raised bed
- amend the soil as required by adding compost, ph adjustments, and so on
- DO NOT add homemade compost unless you are absolutely sure it is slug free
- check around the perimeter of the wooden raised bed for any openings in the structure that a slug could use to gain access to the bed by bypassing the fence - plug any openings with wooden shims or twigs
- remove old wires and staples if you have an old electric fence that is no longer operational. One picture above shows last years wires (aluminum) and staples that I had to remove this year before installing the new galvanized wires.
Up to this year I have been using aluminum welding wire for my electric fence (MIG Electrode Wire). This wire is great for bending around bumps or indentations on the raised bed but it is not very durable in the long run. The wire corrodes easily especially where a slug or other unknowns have crossed or attempted to cross the fence. A viewer of my other slug control video (http://youtu.be/EQ8RFlR0mD4 ) suggested that I try galvanized steel wire and that's what I went with this year. I am writing this instructable well past the growing season, the galvanized wire has stood up quite well over the months since it was installed except for some small rust sections.
This spring I planted the garden and installed the new fence on the same day. Obviously if you can't do it all in one day the fence must be installed and powered up first.
Step 3: Tools and Materials Needed to Make the Electric Fence
Tools and materials required
- a staple gun
- pliers to cut and crimp the wire (when connecting to the battery connector wires)
- a blade screwdriver to remove old staples if present and also to screw the battery box to the raised bed
- galvanized steel wire - any size from about 18 gage to 22 gage will do
- 3/8 inch stainless steel staples
- a box with a removable cover to hold the battery and keep the weather out
- a 9-volt battery connector
- a 9-volt battery
- a multimeter would be handy to test the voltage but is not absolutely necessary (see slug testing in the video)
Step 4: Staple Wires to Raised Bed, Connect Battery, and Test With Meter or Slug
- if desired you can use a pencil or pen to mark a line to guide you when stapling the wires in place
- start stapling the galvanized wire to the raised bed near the location planned for the battery
- staple every 8 inches or so along the wire
- when the circuit around the bed is complete cut the wire allowing enough length to reach and connect to the battery
- you can twist the ends of the wire together and direct them near the battery box location
- start the second run at the same location but spaced about 3/4 inch form the first wire
- twist and direct to the battery box as the first wire
- create two holes in the battery box, ideally on the bottom, for the wires to enter and connect to the battery connector
- double check the wires around the raised bed and bend and staple any wires that are not flat against the wood
- feed the fence wires into the battery box holes and twist them and then crimp them to the battery connector wires
- install the battery and put the box cover on
- use the multimeter to check the voltage between the two wires somewhere outside of the battery box (or use the slug test method - see video)