Bacterial Canker Control for Sweet Cherries

By Gary Thornton and Jim Nugent
District Fruit IPM Agent and District Horticultural Agent
Michigan State University

The use of copper on sweet cherries to aid in the control of Bacterial Canker is a controversial subject. Some growers swear that it helps and other growers don't bother applying it, as they see little value in it. My advice would be that if you're happy with the results so far, then continue the practice. Keep in mind though, that the severity of this disease is greatly influenced by the weather in any given year and wide swings in the severity of this disease should be expected.

When using copper to help control Bacterial Canker, full rate applications of copper should be applied during the dormant to early bud swell period. If applications are made during mid to late bud swell, experience has indicated the need to reduce copper rates by 50%. Once buds begin opening to expose the tender, green tissue inside, then copper may cause serious phytotoxicity. We suggest avoiding application of copper after bud burst to sweets due to possible phytotoxicity. However, if copper is applied between bud burst and bloom, follow labeled rates for blossom blight (generally 25-35% of the dormant rate). Again, we need to indicate that significant phytotoxicity may occur when copper is applied to green tissue on sweet cherries.

The Spray Calendar indicates a multiple application program using Tri-Basic Copper Sulfate for Bacterial Canker control on tart cherries. This is not registered in the same way on sweets due to increased phytotoxicity problems on sweets. Note also that the program indicated will cause leaf defoliation even on tart cherries if applied during warm conditions.

Some additional information on Bacterial Canker that you may find useful can be found in the April 10, 2002 FruitNet or more recently at the April 15, 2003 FruitNet.

Originally published on 4/29/97

Please send any comments or suggestions regarding this site to:
Bill Klein, kleinw@msu.edu

Last Revised: 4-17-03