Prerequisites for Spray Decision:
1. Past history of Monilinia Blight on the farm.
2. Flower buds become susceptible to infection at the F2 stage (bud scales separating).
3. Once fields reach 40-50% F2 and beyond, a fungicide is required within 72 hrs of the start of an infection period. This application will provide 7-10 days protection.
Observations at Tim Strong’s farm as of May 11th, 2011:
All blueberry varieties (including late varieties) are at or beyond the 40-50% F2 stage and mature apothecia cups are present and actively sporulating. There have been four wet periods over the last week with conditions suitable for infection.
Recommendations:
We are at the peak of the primary mummy berry infection period and this is turning out to be a high risk season for mummy berry infection. There have been 8 wet periods suitable for infection at Tim’s farm since apothecia were first observed on April 20th. Of these, four have been over the last week when all varieties have been at the susceptible development stage for infection.
If growers have a history of mummy berry disease they should be utilizing a fungicide program to protect buds from infection. The registered fungicides provide 7-10 days protection and three of them, Topas, Mission, and Funginex, provide 72 hrs back-action control to the beginning of a wet period. The latest prolonged wet period began at 1:00 a.m. Monday morning and if one of the controls was applied within a week prior to this they should have protection. If they did not, they have until 1:00 a.m. Thursday (tomorrow) morning to apply Topas, Mission, or Funginex for back-action control. A 1 hr rain fast is required for an effective application of Topas.
Keep in mind that these recommendations apply to Tim’s farm in King’s Co. only and it is a guide only for other farms.
Refer to “Management of Mummy Berry in Highbush Blueberry” factsheet for pictures of F2 stage and temperature and wetness requirements for an infection period.
Refer to AgraPoint’s “Hishbush Blueberry Insect and Disease Management Schedule” for a list of registered products for mummy berry (Monilinia) control in highbush blueberry.
