Cooperative Extension: Maine Wild Blueberries

6.02.15 Botrytis Risk of Infection, May 29 to June 2

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With the wet weather over the weekend, we have had moderate to high risk of Botrytis infection in fields which already had Botrytis present.   If there was no Botrytis seen before this weekend in your field, it is unlikely there will be more disease now.

Botrytis infection levels are affected by both temperature and length of leaf wetness during infection. The cool weather from Sunday through Tuesday has kept the Botrytis risk low when you consider how long a wet period most fields experienced.   The severity of the disease is affected by the temperatures after infection.  Botrytis will cause increased disease severity (larger lesions with faster spread in tissues) with warmer temperatures.  The cool temperatures from Sunday through Tuesday, which also are forecast to continue through to Wednesday, are not as favorable for the fungus and so the severity of any disease that does occur is likely to be lower (smaller lesions, less spread in the diseased tissues).

The heavy cloud cover affected the cellular coverage for some of our weather stations, so there were gaps in the data we received.  I have noted that in the chart below.

Please let me know how your bloom is coming along, so I know when the risk of Botrytis infection is over in your area.

Thank you,
Seanna Annis