Hello!
I have 3 3 years old pistachio's plants!
Two of them have brown stains on leaves.
The other has no stains and is growing up, but one of the plant with stains doesn't seem to grow more.
What could it be?
What can I do?
I made a research on internet and I found that it could be "Alternaria Alternata", a fungus, so I gave some copper.
ps: i live in Italy and these plants have passed their life in a big greenhouse where my father cultivates vegetables.