Cooperative Extension: Maine Wild Blueberries

5.29.15 Botrytis Infection Risk, May 28 to May 29

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There were weather conditions that provided for some risk of Botrytis infection from the rain storms that came through from Thursday, May 28 to Friday, May 29. Please see the chart below for the risk in your area.

IF you have already seen Botrytis in your field, then you may have more if you were in an area with moderate to high risk of infection.  If you do NOT have Botrytis already in your field, then the weather will have had no effect since you do NOT have any Botrytis spores to be spread and infect the plants.   You should check your clones in full bloom for Botrytis infections in the next few days to double check.  With Botrytis infection, the blossoms will be dead AND have black hairs sticking out of them (use a hand lens to look for them and see pictures below).  If you have dead blossoms and they do NOT have hairs, they were probably killed by Monilinia, mummy berry blight, and there is nothing you can do at this point since Monilinia fungus at this stage will not spread and kill more flowers.

I do NOT recommend any applications of fungicide unless you are sure you have identified Botrytis on your blueberries and there is going to be enough wet weather that if it spreads you are at risk of losing a lot of your bloom.  If you do not have Botrytis already in your field,  there is no point on spending time and money on fungicide applications for problems that do not exist.   Any fungicide application during bloom risks disturbing the pollinators in your field and fungicide residues may discourage pollinators from visiting your plants for a while or cause other effects on them.