Holly bushes have developed small brown spots and could die in time. I should spray them but with what?
You can't know if they're going to die in time until you find out what they have. You also need to do that (find out what they have) to find out what to do about it. Try taking samples to nearest Extension office.
Where are these brown spots? On the stems and branches? Leaves? Are they moving? ...it could be scale...or a fungus. Yes, you need to find out what it is and most likely it can be treated.
Thanking you again for your reply. Do you know what would be the appropriate spray against this insect? Gratefully, Simba