Plum leaf showing brown discolouration
A number of leaves on my young plum tree are beginning to change colour at the tip. They turn pale green and then brown and eventually start to shrivel, although the main part of the leaf remains dark green. (See above).
I first noticed this last week and am not sure whether it is a sign of disease or deficiency. The tree was planted in a sheltered spot in clay soil, with a straw mulch, last autumn. I have two other plum trees, both approx 15 ft away, and neither one is showing these symptoms, nor are the damsons nearby.
The tree also has a number of leaves with round holes (as do the other plums) which I assume have been caused by caterpillars, although I have turned over all the leaves and have found none. There were a (very) few aphids on some young shoots; these were promptly squished.
Can anyone advise me on what I should do?