Latest Mummy Berry Forecast

Friday, April 22, 2016

A quick reminder that primary infection of mummy berry disease in highbush blueberry requires three conditions to be met:
  1. Inoculum presence – mature sporulating apothecia cups,
  2. Susceptible bud development stage – bud scales separating in flower buds (F2 stage), and
  3. Suitable weather conditions – long wet periods at relatively warm temperatures.
Also, it is not recommended to spray until 40-50% of buds of a given variety are at F2 stage and there is no need to spray if you have no history of mummy berry disease on your farm. For more information and pictures refer to “Management of Mummy Berry in Highbush Blueberry”.
                                                 Flower buds at F2 (bud scales separating)


Observations on Thursday April 21st:
  • Apothecia cups at the “pinhead” stage of development were found but were not actively sporulating and as such there is no inoculum at this time.
  • Flower buds are not yet at the 40-50% F2 development stage recommended for spray application.The early variety ‘Bluetta’ had 15% of flower buds at the F2 development stage while Duke, Bluecrop, Nelson, Jersey, and Burlington had 0-4% flower buds at the F2 development stage.
  • Showers and light rain is forecast for Saturday April 23rd and Tuesday April 26th.

Recommendations:

It is still too early to spray as of April 22nd (at Tim’s farm), but we are getting close! There are immature apothecia cups present and buds of some early varieties are approaching the 40-50% F2 stage recommended for first spray. Suitable weather conditions for infection (long wet periods and mild temperatures) are possible within the coming week but most varieties will not be advanced enough to warrant protection. 

Note that several fungicides registered for mummy berry disease (eg. Topas) have what is referred to as “back-action” activity and can effectively control an infection if applied within 72 hours of the beginning of the infection period. For a complete list of registered products please refer to “Highbush Blueberry Insect and DiseaseManagement Schedule”.

Finally, please remember that the observations and recommendations above are derived from data collected in Kings County, Nova Scotia and may not be applicable to your location. Once again, if you are to the south and/or west of Tim’s location in Kings County you may well be ahead in development and if you are located to the east of the Valley you will generally be later. This forecast is to be used a guide only for mummy berry disease management in Nova Scotia. 

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