Q There are loads of bumpy orange spots on my tree branches – what are they and what should I do?

Jenny, Sussex

A That sounds like coral spot, a nasty fungal infection. It is like the plant version of gangrene, setting in during cold, damp weather. The spots should be pinhead-sized and raised, in a pinky-coral colour. I’m afraid there’s no treatment, so cut off the infected branches and burn them. Don’t put them in the compost, or you risk spreading the infection, and don’t leave them to fester in a pile.

Always prune in dry weather, and cut the branches off at the collar (the thick part at the base of the branch). This is better than leaving a snag (a stub or stump), as the collar heals faster and the snag could be infected without showing outward signs of it.

Also keep an eye on other wood in the garden for signs of dieback, which is an early sign of infection. Damp, dead wood is especially vulnerable – check things like old hazel peasticks.