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Cold wet weather favorable for cherry blossom blast

Written by Dr. Youfu “Frank” Zhao, Professor & Endowed Chair in Bacterial diseases, WSU-IAREC, May 3, 2022

Bacterial canker risks we experienced in April 2022 and what growers should be looking for to assess damage in the orchard.

The weather conditions that we experienced in Mid-April, especially later that week (April 15) was ideal for Pseudomonas to cause damage to sensitive tissues of cherries (blossom and young leaves), leading to frost injuries, which was partly due to that Pseudomonas promotes ice formation at temps of 26 to 32 °F. Blossom blast could be developed after a prolonged periods of cool, wet weather and low temperatures close to freezing (~31 °F), which could be further induced following a freeze, leading to severe blossom blast symptoms.

I visited a cherry orchard in Yakima area on April 13 (Wednesday) and the orchard had a history of bacterial canker disease (Figure 2).

Canker and Gummosis

Figure 2 Canker and gummosis

However, I observed two practices that could make bacterial canker worse. One observation was that they did pruning too late in the spring, and you can see a lot recently  cut young shoots on the ground (Figure 1).

Recently cut shoot with green bud

Figure 1 Recently cut shoot with green bud/flower

The second observation was that they planted a lot of young trees intermittent with old trees, which carry a lot of pathogens as shown in figure 2.

For more information about bacterial canker in Washington sweet cherries see here


Youfu “Frank” Zhao

Professor & Endowed Chair in Bacterial diseases, WSU-IAREC


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