My grapefruit tree has yellow leaves with black spots?

Question

My grapefruit tree has yellow leaves with black spots?

Answer 1

fungicide

Answer 2

Yellow leaves are nutrient deficiency. You need to fertilize with a citrus fertilizer to provide acid and keep reasonably moist during this hot weather.

The black areas are probably sooty mold due to aphids. There are a number of effective sprays.

Answer 3

Back off on the water.  Keep weeds or other plants clear of the crown and make sure the crown is not too wet.  It is some kind of leaf spot and is caused by a fungus or bacteria, can't remember which.  Usually from too wet conditions.