A few of the fruits on my young peach tree have developed a blue-coloured mould on them shortly after picking, what is this and is there a cure?
This is blue mould, and is a species of Penicillium, a parasite that infects injured / damaged tissue.
This damage could have done by wasps, birds or bruising when picking them.
When storing the fruit, select only the ones that are completely free from skin damage, and keep them slightly apart.
There is no practical way to prevent this occurring.
Is there any summer control for peach leaf curl?
The best action in summer is just to remove the infected leaves, ideally before they develop any sign of the white, powdery coating which indicates spore production.
Next spring, spray with a copper based fungicide, and keep the plant protected from rain and this should greatly reduce any spread of infection.
Some of my peaches are rotting and have developed buff coloured rings on them, what caused this and how can I prevent it happening again?
The rotting is due to the brown rot fungus.
This results from damaged tissue, possibly caused by wasps or birds.
Prevention is rather difficult, but catching wasps in a trap and using netting to deter the birds may help.
My dwarf peach tree's leaves have turned pale and there is fine speckling on them, can you help please?
Your plant is being attacked by red spider mites.
Plants that are subjected to a shortage of water, or are growing in a very dry spot, are more prone to attack.
Try moving the pot to a more sheltered spot, keep it well watered, and spray the leaves daily with tepid water.
To control the existing attack, spray with an insecticide based on fatty acids.