Thanks for doing the blog, really helpful. My Euphorbia Ammak Variegata has recently gotten some brown discoloration in certain patches (images attached). I’m in San Diego and the plant stays indoors. It’s just been repotted (1 month) into a new terracotta pot and is about 4 feet tall. I just noticed the discolouration and it seems to be in fairly discrete vertical patches. What have noticed is that the “damage” seems to be on the front and sides that don’t face the wall.
The plant still feels quite firm at the discolored regions (I first panicked that it was rot!). I have had the gas heater on lately due to the weather but I dont have the room too hot, could that be something?
The discoloration in the photo is worrisome… if it was outside i would say it is sunburn with a possible secondary infection… inside, unless it right near a window it is more likely to be just an infection (virus or fungus). I would say you should stop watering (Until March) and treat with a fungicide like Neem Oil ( a natural, effective product that is not chemical warfare in your home…). Use a 1 or 2% solution in water with a splash of liquid soap as an emulsifier (about 1tsp. to a quart of water) or buy ready to use. You should be able to find it locally at a garden center. Spray liberally and reapply once a week at three times. Hopefully that will take care of it. If it continues to spread or starts turning black you may have to do an amputation above the infection and re-root the unaffected top, but hopefully you can stop it before it gets that far.
Good luck and take care,