I read this in New Scientist, I believe.

Take a battery that's apparently drained (doesn't work in your walkman
anymore, for instance). It will most likely have some sort of voltage
left in it, though.

Put the battery on the ground near your precious strawberries. Connect a
loop of un-insulated wire to one end, and another to the other end.
Place the loops so they are around the strawberries, one within the
other, so the wires are within a few millimetres of each other.

Now, whenever a slug smells your yummy strawberries, it will get an
electric shock if it tries to approach!

Haven't tried this, but I thought it was worth mentioning.

Kae