Cooperative Extension: Maine Wild Blueberries

Monilinia infections: May 2 to May 4th and upcoming May 5th to May 7th

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I suspect there are mummy berry cups across all blueberry areas, unless it is a very late field. The flower buds also seem to be at least 40% F2 or past that in development. The rain during the last two days produced conditions to cause Monilinia infections from Friday May 2nd evening to May 4th morning. Please see table below for possible infection periods in your area. Some of our weather stations were not put out yet due to repairs and some are not sending signal well, but I think the range of where working stations are located suggest this was a long enough rain event to cause Monilinia infection in all Midcoast and Downeast areas if the plants were susceptible.

If you applied fungicide to your plants after April 22 to 25 (10 to 7 days before) your plants were probably protected during the infection periods this weekend. Most protectant fungicides are effective for 7 to 10 days after application depending upon the weather. The best way to protect your plants is to apply fungicide before an infection period occurs.  If you were not able to do that, you may get some decrease in disease if you apply a propiconazole based fungicide by May 5rd evening.  These fungicides penetrate into the first layer of the leaf, so there is a chance these fungicides will kill off some Monilinia infections that have only penetrated to that level in the leaf.  This is not a cure for all infections, which is why applying fungicide before infection periods will be the most effective method of control. Please check with your processor on which fungicides they will accept.

The rain forecast for Monday May 5th evening through Tuesday night and possibly into Wednesday is likely to create conditions for Monilinia infections. If you have applied fungicides after April 27th, your plants will probably be protected for these upcoming conditions.

Please check your mummy berry plots and let me know how they are doing.  Seanna Annis