Posted: 17/02/2014 at 22:42
Oh bad luck, Ruth. Honey fungus is a baddie. BUT - don't despair. We moved to our house 13 years ago, and soon found that our (big) garden is riddled with honey fungus. i panicked! My first reaction was to do everything I could. There was a product on the market then called Armillatox which is partially effective as a protection for trees - they are not allowed to market it for that use now, but the product still exists as a surface cleaner. I think it had some limited effect.
But after a year or two I realised that the fungus was only killing old and weak plants (and very slowly). And Armillatox stinks. So now I'm more laid back about it. i know that three more trees are infected and will, therefore, die....but probably not for two or three years. So I'm spending that time planning what I'll put in their places. I've learned that some plants are really susceptible - for example viburnum - so have adapted my planting plans. The RHS website gives a list of plants that are more resistant than others.
So, strictly if you want to try to halt the spread of the disease you show remove any infected plants, dig out all of their stumps and root systems. You could even line any new planting holes with butyl rubber to combat infection, and fill with clean compost. But that seems like quite a lot of work to me (I'm a lazy gardener I guess!). So personally I'd be inclined to continue to enjoy your much-loved willow tree while it finishes its life, and remove it only when it gets ugly. In the meantime you could take some cuttings from it to keep it's history alive.
I'm sure others would give different (and probably better!) advice, but I'm just sharing my own experience....
Let us know how you get on.