Diseased Lemon Tree

Can anyone tell me what this is on my lemon tree (see pic). How do I get rid of it?

Don´t know what it´s called but get a spray bottle with water and a drop of Fairy liquid, spray the whole tree a couple of times and it´ll be gone.

Looks like sooty mold fungus . . . . apart from being unsightly its not very damaging in itself.
Its caused by aphids feeding on the leaves and excreting honeydew which then grows the mold. The treatment is to kill off the aphids with an appropriate spray (Ferretera or Garden Centre) and then wash tree down with a horticultural wash to eradicate the mold. Best to remove heavily contaminated leaves and bin them (don't drop on ground) and clean hands/tools before treating.

Thank you for your help and suggestions. Can you tell me what you mean please by a “horticultural wash”. Thanks

Its a non toxic disinfectant/fungicidal wash specifically for removing fungus and or bugs . . . as said above, if its only a small amount spray with bug spray 1st, wait a day or two and then wash down with slightly soapy water . . . it should be sufficient, if it comes back then go the horticultural wash route . . .

If its mould resulting from aphides, it is possible that the aphides are being farmed by ants, who milk them for the nector. Have a look to see if you can see ants running up the trunk to the aphides. If so try puttingant killer around the base, or if you can get gell, then as a band on the trunk. But also remove the diseased leaves as recommended before.

If you take one of the affected leaves into a garden centre and show them, they’ll sell you the correct product to get rid of it.

Washing up bowl with warm water and washing up liquid. Throw over the tree every now and again, should keep tree disease free.

Our tree has multitudes of Lemons and I never use pesticides and rarely water it. In the Winter and rainy times the tree stores water and then can survive the Summer with hardly any watering.

My mantra is a Lemon tree thrives on neglect. Just needs pruning to keep in shape as they do grow very quickly.

The timber from dead fruit trees , espcially apple and cherry, is very valuable, because its beloved by wood turners, but need sto be at least 4-6 inches diameter, and knots are good.. Saw it into say 12 inch lengths and sell it on ebay