not that i know of . we have a lot of willows in sunny thetford and they all look lovley . just as a experiment it mite be worth wating till your willow is dorement and cut a piece of this summers growth of of it and plant it in a pot . keep watering it and it should become a healthy young tree next summer and it will give you an idea if your tree is ok . it mite be worth digging in a tube down to the roots and watering the tree directly as its been quit a dry spring realy . ps if you do the experiment you can donate the sapling to someone or plant it somewear wild near a river . just a thaught . i did it with about a 3 foot branch about 3 winters ago . its now about 12 feet long and hanging in the river looking lovley .

You don't say where you are in the UK, but its possible there was some damage to the bark of the tree during the harsh winter, and that's why its struggling. Alternatively, drought - in the south, we had serious drought this year, so a spell of rain might encourage leaves, and then they just die because the water supply dries up again, and willows are thirsty plants.
Those are the simple things - there are many other things which affect willows - Willow black canker, Willow Scab etc. Willow Leaf Beetles graze the leaves and they all die - the pest leaves, but returns when new growth appears, so could be that.

Thanks - here in 'sunny Cumbria' we've not had any drought at all, been great (not)! It's just the contorted willow that's suffering, all the others are fine, in fact we seem to have an invasion of pussy willow seedlings popping up just about everywhere!
The bark looks ok, a bit of damage in one place by the 'blasted woodpecker' but not enough to do any real damage - he has a go at everything!
I've not noticed any beetle nibbling in/on the leaves.
The poor tree is trying really hard to rejuvenate, popping out new growth along its branches, but it just dies away after a bit and the branches are dying back alarmingly

if it still lives till winter i think its worth doing the experiment i said above . sounds like your willow has something more drastic wrong with it . its well worth asking a tree surgeon what the problem is . i will ask my friend who specialises in bonzie trees and is very knowladgable excuse my spelling with plants in general but especialy trees . he has over 50 of them .

Yes, I've potted a few cuttings so we'll just have to see. It's such a lovely big tree it's going to leave a big hole if it has to come down :o(

well the up side is willow grows realy quickly so it wouldnt take long to replace if you do lose it .