Mummy Berry Blight forecast Thursday April 26, 2012

Knox, Lincoln and Waldo Counties
Numerous pinheads and mature cups are still present at Appleton, Liberty and Belfast.  Mature cups producing spores are probably present throughout this area.  As mentioned before, the plants are susceptible as long as cups are present in your field. 

Hancock and Washington counties
Numerous pinhead and mature cups are still present through out fields in these counties.
The fog the last 2 nights in many fields was NOT long enough to produce infection periods.  Temperatures on Thursday night did dip to 25 F for 2 to 3 hours in some fields, but this is not likely to cause cold damage to most plants.  Some clones may be very sensitive to cold but most should have not have damage.

All areas
The rain forecast for Thursday night through to Friday will likely produce another infection period for the fungus to get into the plants.
If you applied fungicide to your plants on or after Thursday April 19th, your plants will be protected during this coming infection period. 

I will update the forecast on Friday afternoon as to whether infection periods occurred or not.

Factsheet on Cold tolerance effects on flower buds and irrigation 
This study by  Dr. Paul Cappiello did not hold plants at different temperatures for long periods of time and did not examine the extensive diversity possible in clones.  It does provide a rough estimate of when flower buds are most susceptible to frost.
 
http://umaine.edu/blueberries/factsheets/irrigation/flower-primordia-development-stage/