Thursday, April 7, 2016

Damage to blackberry flowers at 27°F

There are reports coming of damage to blackberry flower bud from the freeze on Feb 5/6.
Make sure you check your fields to assess damage.  Left  image above shows shoot damage, leaves and buds were killed. Right image above shows flower bud damage. The center part also called the receptacle is the part of the flower that eventually develops into the fruit.

What to look for:

  • The buds will look green but if you cut them open, the center will be brown/black.
  •  The leaves may look fine or if it was really cold the leaves will also show damage as in the figure above. 

Fumi Takeda, USDA-ARS in West Virginia gradually exposed blackberry buds to cold temperatures, and unlike other berry crops, found that the killing temperature was 27.5 °F for all stages of flowers. Here his data:

What he found:

  • Critical temperature is between 27-28° F.
  • Within a flower, organs that will comprise the fruit were more susceptible to freezing temperatures.
  • Within an inflorescence, all open and unopen flower buds produced exotherm (were damaged) at the same time.  
  • In spring, blackberry (flower) has little or no freeze tolerance.

What can be done for the upcoming weekend freeze to minimize more damage:
  • Make sure any cover crop is mowed as close to the ground as possible to move the cold layer closer to ground
More information will be posted as we assess the situation.

For more information see links from previous years:

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