Don't know what it is about this year, but I've never seen so much Thrush mid summer. Maybe it got really deep into the nooks and crannies of hooves in the long wet winter and has been lurking unseen. I think so far I've probably found it in 9/10 of the hooves I pick up.
Certainly I am finding it in otherwise well kept hooves, deep in the bottom of collateral grooves, tucked under the 'nose' of the apex of the frog, nicely covered by odd flaps of loose frog or perfectly protected under shoes. Owners are usually horrified because by and large they are pretty good at the routine foot picking etc.
I am also seeing Thrush a lot in horses kept on rubber mats and/or straw. Anything which is allowing the hooves to get damp with urine. Pee as we all know degrades keratin, leading to a softening of hoof walls and soles and leaving the white line and frog vulnerable to secondary infection.
So please for the sake of your horse do not treat Thrush as the trivial condition that the old texts (and old wives and some YM) would have you believe. It causes pain in the back of the foot. This pain can be minor and relatively unnoticed, or more extreme where the poor sore horse that has to land very toe first to avoid loading the back of the foot. (The horse may also stand with their front legs jacked back under the belly somewhat to avoid loading the heel. When they do this they can't use their stay apparatus properly.)
If you have a horse with heel pain you risk receiving a diagnosis of navicular, with all the associated anxiety and expense and possible fatal consequences.
This is so common it's gone beyond tragedy. However the discussion regarding navicular, it's existance, treatments and prognosis deserves a separate post (coming soon).
So, if you suspect Thrush, treat it (and it doesn't have to be black and smelly). So long as you use a suitable preparation you won't do any harm and you may well save yourself and your horse a lot of heartache and pain. Oh and keep the beds pee free and make sure your turnout is not a urine bath. If you can smell pee, then Houston we have a problem.