Results:

As long as the fence electronic fence is clean it works very well. One can observe snails approaching the electric band and turning back. Unfortunately with a few rains the fence get dirty (the rain drops  fall on the soil and splash the wet soil on the fence make the soil covers the fence) and looses the efficiency. One could clean it regularly but it is cumbersome. We may try to fix the band on some kind of plastic fence high enough, probably 20 cm so the the band with the electric line will not get dirty.