What's the problem with this star ruby grapefruit?
I have this star ruby grapefruit in a pot.
I noticed this strange brown spots on the back of some younger leaves.
These young leaves where lightly affected by whiteflies with production of honeydews.
I sprayed some Bordeaux mixture.
I wonder if perhaps this brown marks are the plant's reaction to the penetration of the mouthparts of the whitefly (called a stylet). Grapefuit can have brown spots due to Alternaria fungal infection http://edis.ifas.ufl.edu/LyraEDISServ...
But I dont think this is that problem. The next step is to monitor some of the spots and see if they are spreading. If you not longer have whitefly and the spots are spreading then its suggests a microbe.
The Bordeaux Mix is of course to be used against fungi and watermolds. You may want to consider taking images and storing them in a Plant Journal here on PlantVillage