We planted a new garden last year and have included several fruit trees. This year our victoria plum is covered in some kind of bug infestation causing leaves to have a silverly appearance. Nearby apple trees seem to be unaffected. At first I thought it was the dreaded 'silver leaf' fungus but since I can definitely see little bugs moving about I hope I can rule that out.

Can anyone suggest what infestations plums are prone to and what's the best remedy?