Elisabeth C. Miller Library

Gardening Answers Knowledgebase


Knowledgebase record #554


PAL Question

We have a mature ornamental cherry or plum tree that suffered from brown rot last year. We removed all affected branches and leaves. We were told that we might need to do something else this winter or spring--spray the tree with something, possibly. Can you advise us on how to keep our tree healthy?

Answer

I consulted The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale Press, 1996), and this resource recommends doing what you already did, by removing and destroying affected parts of the tree. At the beginning of the growing season (early spring) you can spray sulfur to control this fungal disease on blossoms. If you were growing fruit, you would spray again later in the season to protect the fruit, but since this is an ornamental tree, it isn't necessary. Copper sprays are also used to control the disease. Washington State University Extension recommends preventive measures, such as avoiding wounding trees (damaging bark with string trimmers/weed-whackers/lawnmowers, or making bad pruning cuts). Avoid wetting the blossoms and leaves, and keep the tree pruned for good air circulation in the canopy. Avoid excessive nitrogen fertilizer. While the tree is in bloom, check it frequently for symptoms, and destroy any diseased parts as soon as you notice them.

I found sources for less toxic (but still not hazard-free) versions of these fungicides from Peaceful Valley Farm & Garden Supply, but they may be available at your local garden center as well. Some of these require a pesticide handler's license.

Lime Sulfur Fungicide

Copper Sulfate

Keywords: Flowering cherries, Trees--Diseases and pests, Prunus
Date: 2007-10-11

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