Yes, I have lots of people complain about puckered leaves on plums. It sounds like aphid and these little buggers really explode with the hot weather when the plum tree gets stressed. Try spraying the foliage with insecticidal soap two to three times in one week - but not when the sun is shining or you will burn the leaves. Follow the instructions for aphid control on the label. A strong jet of water on the leaves two or three times a day can also help in the spring when the aphid colonies are starting to form. Plum trees need one inch of water a week at least, and the water needs to be consistent. Set a soaker hose around the trunk and cover with a mulch to hold in moisture. This will help the plum send out new leaves if the insecticide spray causes leaf drop. Keep growing, Marianne Binetti