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 April 27th, 2011:
Early varieties are now at 25% F2 stage and apothecia cups are starting to sporulate. An extended wet period from 6:15 a.m. April 26th until 3:15 p.m. April 26st (9 hrs) with average temperature of 9.5 °C presented suitable conditions for infection. A second wet period from 3:30 a.m. until 2:00 p.m. today (April 27th) with an average temperature of 10.6 °C also presented suitable conditions for infection.
Recommendations:
Although bud development stage is still slightly earlier than the recommended 40-50% F2 stage, there is inoculum present and there have been two suitable wet periods for infection in the last 36 hrs. If a spray with Topas, Mission or Funginex was made prior to Tuesday’s (April 26th) wet period, up to 14 days protection can be expected. If not, growers have 72 hrs from the beginning of the wet period on Tuesday (6:15 a.m.) to apply one of these controls. Therefore, an application would need to be made prior to 6:15 a.m. on Friday, April 29th to provide back-action control. For intermittent wet periods such as we’ve had this week, Topas is a good fungicide choice as it requires only a 1 hr rain fast.
Keep in mind that this recommendation applies to Tim’s farm in King’s Co. only and it is a guide only for other farms. If you are west or south of Tim you may well be ahead of him in development, and if you are east of him you may well be behind him in development.
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.
