Answer: It does sound like your trees are getting too much nitrogen, since plums do best in a moderately fertile soil rather than an overly rich soil. It's not fire blight, which attacks pears and apples, but not plums, but it may be the work of the Oriental fruit moth. The caterpillars (pinky-gray, up to 1/2" long) burrow into the stems just below the wilted area. The adults are dark gray moths with mottled wings. If these are the culprits, prune off and destroy the affected twigs. There are several generations per year, so prevent them from attacking fruit later in the season by spraying summer oil after the second generation eggs have been laid. Your agricultural extension office (ph# 402/729-3487) can tell you when the moths are actively laying in your region, so you'll know when to apply the summer oil. To foil the emergence of the first generation next spring, cultivate soil around the trees to a depth of about four inches before bloom, being careful to not damage tree roots. I hope this does the trick!
Q&A Library Searching Tips