Roses have lost lots of leaves

What is happening to my roses? I’ve been treating them with Roseclear3 at fortnightly intervals, but some of the branches are becoming completely defoliated. They seem to be worse after spraying and all varieties are affected.

Rose fungicides available to private gardeners give protection up to a point. But where lots of roses are grown together and when conditions for disease are favourable, even regular spraying can sometimes break down.
This year is turning out to be bad for black spot and I’ve also seen a lot of rust.
You are unlikely to clean up your plants completely this late in the season. The most susceptible varieties will probably defoliate by mid-August and flowering will therefore reduce. However, it is worth taking action now to minimise the disease problems.
Step up your spraying programme to a weekly treatment and ring the changes with your fungicides. As well as Roseclear3, try Systhane Fungus Fighter, and sulphur-based, organic fungal treatments.
Make sure your sprayer is scrupulously clean, particularly if it is ever used for weedkillers, and that the fungicide manufacturers’ instructions are followed.