You can't, I'm afraid. The toadstools are just the fruiting bodies of underground mycelium - if you don't like the look of them, just twist them off, preferably into a plastic bag in case they're the type that spread from spores in the gills beneath. Usually a temporary problem at certain times of year, althouigh with all the wet weather this year, there are many more of them about.

Thankyou Bamboo we will try this out and see what happens.