The Q&A Archives: New Leaves of Plum Turn Brown and Fall

Question: I have a number of american plum trees (about 4 years old), this year they are having a leaf problem. The new growth is turning black/brown, shriveling up and falling off. The trees are planted up by the chicken coop, they get a lots of water, and lots of chicken manure. Can plums get fire blite? Or is this due to an overabundance of nitrogen in the area? The second year growth does not appear to be effected. But I have lost nearly all of this years new growth. Also there are also a number of small wasps only about 1/2 inch long that crawl around only on the affected leaves. They are brown/black in color. Should I spray for these or let them be?

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!

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