Beech hedge infested with white fly
Beech hedge is 18' long & 6' high, our front boundry. Each year it has white fly, but this year it is absolutely covered. To extent that if people brush past on the pavement they are covered in them. We've blasted with hose, blasted with soapy water, no improvement. Does anyone know of a systemic treatment that I can water in? Don't fancy trying to spray that lot.
The hedge was pruned well back last Autumn and won't take another haircut as of now.