Posted: 07/11/2017 at 09:27
Please can you clarify something?
To my knowledge the only Griselinia which grows in UK is Griselinia littoralis...
"The leaves are alternate, leathery, glossy yellow-green above, paler and matte below, 6–14 cm (2–6 in) long, oval with a smooth margin"
This doesn't seem to compare with what I can see in your pic.
If this a different sp in a different country that will affect answers you may be given.
Diseases will be very different from here in UK.