Introduction: Electric Garden Slug Fence

Picture of Electric Garden Slug Fence

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

But occasionally an innocent worm will get zapped while trying to cross the fence... 

Step 2: Prepare the Raised Bed Soil and Frame for Planting and Wiring

Picture of Prepare the Raised Bed Soil and Frame for Planting and Wiring
Tips to help you have a successful growing season:
  • 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

Picture of 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

Picture of 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)
                                                           That's it - simple, inexpensive and effective!

Comments

seleniebeanie67 (author)2015-03-08

I have a community garden with 50 beds and slugs are a huge problem. I was considering trying this method on a few beds...but there are children always running about and I'm concerned about them touching it and getting a zap - any ideas folks?

rustille (author)seleniebeanie672015-03-15

Hi, this is safe for children, it would be the same as if they touched the top of a 9v battery, i.e. you wouldn't feel anything. The 12v option should also be safe, however at this voltage you would get a small jolt (most farmers' electric fences are 12v).

gustavio101 (author)rustille2015-04-12

My father and my grandfather are farmers and the fences are actually putting out 4-12 KV! No you didn't read wrong. Still it won't kill you unless you have a weak heart.

rustille (author)gustavio1012015-04-13

Are they keeping velociraptors? ;-)

gustavio101 (author)rustille2015-04-13

I dunno what you mean with velociraptors, I'm not from England neither can google translate define it ;)

kanemaui (author)gustavio1012017-05-24

OMG!!! Bout fell outta' my chair!! A 'Velociraptor' was a type of dinosaur similar to a T-Rex but much smaller and faster and deadlier, as in ability to rip you apart ~ ~ ~

Insomnus (author)rustille2015-12-06

Farmers fences are powered by 12v car batteries - but they are boosted to several thousand volts. They have very low current, but still enough to fry a slug.

nlinventor (author)rustille2015-04-13

A couple of notes on using 12-volts. First: I tried 12 volts (a series of AA cells) and found that the slugs were more often killed rather than just turned away. Second: NEVER use a high current 12-volt battery for this application (such as a car battery). The current supply capability is way too high and a short circuit between the wires would cause them to get very hot. However the 9-volt battery works just great as the internal resistance of the battery limits the current so there should not be a problem even with a short.

wolfkeeper (author)2016-06-16

I tried this with copper wire and a 9v battery, but it doesn't seem to be working for some reason; the snails just go straight past it. Does it have to be galvanised?

gustavio101 (author)wolfkeeper2016-12-03

Did you check if the copper wire was isolated? Most copper wires have a thin coating of isolation. You can either try to remove that or just get another wire.

wolfkeeper (author)gustavio1012016-12-04

I stripped off the insulation, it was mains electrical wire. Didn't notice any slugs but there were snails that had got past.

gustavio101 (author)wolfkeeper2016-12-04

Hmm, what voltage did you use? 9 Volts is a minium I would say. If that doesn't work connect a big capacitor containing 400 V, that should make them fly off the fence.

wolfkeeper (author)gustavio1012016-12-04

I used a rechargeable NiMh battery. I measured it at 8.4v.

Maybe snails are less sensitive.

nlinventor (author)2016-06-16

Seems as though once they have been tingled by contacting both wires simultaneously they then associate just contacting a one wire as a bad thing. I refer to this in terms of "Pavlov's Slug" in the video :)

scott.cairo (author)2016-06-06

I wonder if for a smaller area one could use those £1 solar garden lights.maybe not enough voltage. (about 1.5. i think) ?

nlinventor (author)2016-05-31

That looks good!

nlinventor (author)2016-05-19

For simplicity and safety I recommend a 9-volt battery for this application. The battery typically lasts for a full growing season (assuming the wires are mounted as shown in the instructable). In one experiment a number of years ago I found that 12-volts tends to "fry" the slugs rather than turn them away. Good luck with whatever method you might try.

nlinventor (author)2016-05-19

Look forward to your observations. Even though you have a reduced voltage (12 volts) and the mains connection is indoors it still might be a good idea to have the system connection through a ground fault interrupt type of circuit. There is always a chance of some kind of short between the primary and secondary of the transformer (if used).

Bryonycraze (author)2016-05-11

I've made this and it's fantastically effective, thank you. However I live in a wet area so my wire has rusted in places and the snails just crawl over the rust. What wire do you use? I considered using stainless steel but is this a good enough conductor?

nlinventor (author)Bryonycraze2016-05-11

Yes I now use small diameter stainless steel welding wire. I forget the diameter but the small the better as it will be easier to form around the raised bed. In terms of electrical conduction it is just fine and it should last a good number of years. I have tried aluminum welding wire and galvanized wire but both have a limited life in this application.

Bryonycraze (author)nlinventor2016-05-11

Great thank you, I shall look for some. My friends and family have been most impressed with your idea and think you could make a fortune if you sold this as a kit ?

nlinventor (author)Bryonycraze2016-05-11

Thanks! Will pass on the kit idea but I would not have any objection at all to someone else giving it a try.

rustille made it! (author)2015-06-01

Hi, thanks for the Instructable, I made it and it's working perfectly. I'm not much of a guru with electricity, but is there a way to set this up like one of those piezo-electric tennis racquet style fly swats? I imagine the battery would last much longer this way. If you know how to do this please let me know.

electric guy (author)rustille2016-03-31

ur right

nlinventor (author)rustille2015-06-01

Thanks for the pictures. Many thousands have viewed my slug control videos over the years but this is the first pictures I've seen of some one actually having the slug control system in place and working. Not sure about the electric tennis racquet operation so won't attempt to make a suggestion on it... but the 9-volt battery typically lasts for the whole growing season so no big deal re life span. I noticed that you have your wires running on the top edge of the raised bed border wood. Might have a chance of the battery draining faster due to standing water but I don't think it will be a problem.

rustille (author)nlinventor2015-06-01

I'm glad to have brightened your day! I'm sure the battery will last long enough, it was just the engineer in me thinking of ways to improve the system. I placed the wires on top due to one edge of the bed being fixed to the privacy fence, I tested my circuit in heavy rain with a voltmeter and it doesn't appear to be shorting out. I will keep an eye on things and report back later in the year.

holymoses (author)2015-08-10

Isn´t a simple combination of copper and zinc without any active electrical power working well enough?

...and how to parry this little one:

http://www.sapnet.co.za/bookcovers/2/7/3/978273383...

:-P

nlinventor (author)holymoses2015-08-10

Catching the flying snails a bit tricky :) I did a fairly reasonable comparison of several slug control methods but none compare with the method described. Here the other instructable https://www.instructables.com/id/Comparing-slug-control-methods/

electric guy (author)nlinventor2016-03-31

what the heck is a flying snail?
wierd little project but I luv it!!!

holymoses (author)nlinventor2015-08-10

"The video also shows that my "brilliant" idea of having the slugs slime
create a voltage when it connects between a copper and aluminum
conductor didn't work either."

Exactly what I meant. But this now is astonishing me, I think I also have to do some research and review about this. Probably aluminium is not the perfect material of choice. I am still thinking of zinc!

But for your better idea here the next step could be solar powered!

:-)

ladyelsinore (author)2015-03-07

Hi, I was wondering if it is possible to do this setup on the bottom of a chicken coop to deter rats? :)

nlinventor (author)ladyelsinore2015-04-12

Check out my other instructable re Electric Fence for Mice. That might be worth looking into for rats. But you can get a nasty little shock using this method but I think it will keep the rats out. Here's the link https://www.instructables.com/id/Homemade-electric-fence-for-mice/

gustavio101 (author)ladyelsinore2015-04-12

sure, but rather use a capacitor, but not over 100v that may be dangerous even for people.

dondichandler (author)2015-02-04

A great idea which I plan to try this sping. A question. Does rain have any effect on the effectiveness of this (short circuit)?

nlinventor (author)dondichandler2015-02-04

Nothing noticeable or easily measurable. The relatively low voltage combined with the wide separation of the wires and the insulating characteristics of the wood all work together to make current drain, even when wet, minimal.

jon.blymiller (author)2014-10-14

I watched the video. I have a bean garden and the slugs are terrible when it rains... i applaud you!. (also the sound effects made me laugh )

nlinventor (author)jon.blymiller2014-10-15

Thanks jon... yeah around here they do a lot of damage throughout the growing season.

heartwork (author)2014-06-03

This is one of the articles which motivated me to do my own electric slug fence project. Although I do not have raised beds, I made my fence on the ground, using some old planks - and it works. Number of slugs on my salad after installing it = 0. I made a blog entry about it (hope it is not intrusive): http://spacepetuniareview.blogspot.com/2014/05/slug-wars-chapter-1-making-diy-electric.html

Cheers!

gabigirlhs (author)2014-05-06

Just made two....let the growing season begin!!

One question to you all..... how do YOU test your snail fence? ???

nlinventor (author)gabigirlhs2014-05-06

Other than what I did for the video (placing slugs near the fence) you could use a simple multi-meter (VOM) set to voltage. Measure the voltage between the two wires anywhere along the run (not at the battery terminals only). I'm thinking that anything above 4 volts should work.

gabigirlhs (author)nlinventor2014-05-06

I tried that with a battery tester. Do I have some wrong thinking going on there? I thought that would work. It didn't show anything. I ended up doing the tongue test. That did work. ;-) I was hoping to find another way though.

nlinventor (author)gabigirlhs2014-05-06

Wonder if you tried the tester at the battery terminals? If it showed voltage there then there's a good chance that you need to make better contact between your tester and the wires by just pushing hard against the wires with the test pins/clips (I'm basing this on the positive results of your tongue test).

maximzodal (author)2014-04-27

I like it. Simple, and effective. Very good information.

maximzodal (author)2014-04-27

This guy got tired of deer eating his garden every night and hooked a live 110v wire about three feet high around the perimeter. Yeah, I know, dangerous as hell. I'm not advocating this. Early every evening he would plug it in at the house and it worked, no deer. So, one night he forgot to plug it in until right before going to bed. Next morning he found three deer inside the garden.

confu (author)2012-11-04

A few days ago I thought about a modified version of this, for teaching a cat that enjoys pissing at our terrace door a lesson.
There are some metal stairs outside the door on which the cat must be standing while "marking" the door.
I will try to connect one pole of the 9V battery to the metal grid and make kinda spiral of wire that sticks to the door and connect it to the other pole.
I´m curious ;) Evil cat!

pcooper2 (author)confu2012-11-28

Your idea has a very low probability of working. There was an episode of the "Mythbusters" television show wherein they tested the story of a railway worker being electrocuted while urinating on the third rail. They used a dummy rigged to emit a stream of salt water to simulate a urine stream. High-speed photography revealed that the "urine" stream was breaking into droplets as it fell, and thus the electric circuit was not being completed.

maximzodal (author)pcooper22014-04-27

I agree with finton, I've seen the effects of peeing on an electric fence and it was 'jolting'. Also on a small gas engine spark plug.

finton (author)pcooper22014-01-01

And yet the idea worked fine when I peed, in the dark, on a farm's electric fence many years ago...

darkisland51 (author)2014-04-10

A question: Where do get the battery connectors? I can imagine pirating an old flashlight or some other dollar store-type item. If you update this instructable, could you add some pictures along this line, and additional instructions?

nlinventor (author)darkisland512014-04-12

darkisland51 - 9-volt battery connectors are available from electronics supply stores such as Radio Shack and The Source.

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