I bought three bare root fruit trees recently: a braeburn apple, conference pear and a victoria plum. All on dwarft rootstock for patio planting. All three started to produce leaves within a week and seemed healthy. The apple still is, but the pear and plum developed black/brown edging on the leaves and have not grown since (for approx 3 weeks).
No sign of any bugs on the trees. Any suggestions what it could be?
I have attached a couple of pictures of the pear tree leaves. The blue residue on the leaves is Bordeaux mixture - in case of a fungal infection.