Mummy Berry 2020 - Post # 6

Monilinia blight (mummy berry) infection period Saturday May 16 for highbush blueberry.

Rain started overnight last night (16 May 2020), when temperatures were just above 10 degrees C.  The temperatures have since dropped (approx 6 degrees C at 1 pm) but with over 12 hours of rain (100% leaf wetness), we have likely experienced infection periods in most regions of the Annapolis Valley.  

Temperature and wetness conditions required for Mummy Berry infection.

On Friday May 15^th, Sajid confirmed that the early block of Duke he is monitoring now has 81-85% of floral buds at F2 (bud scales have separated in the flower buds), as shown in Figure 1.  The medium maturity variety has 40% of the floral buds at F2 stage (Figure 2) while the block of late variety, only 15% buds are susceptible to Monilinia blight infection (Figure 3).

Figure 1. Floral buds at F2 stage of development.

 Figure 2. Mid maturity variety, floral buds at F2 stage of development.

Figure 3. Late maturity variety, floral buds at F2 stage of development.

If your planting has not reached 40-50% F2 (bud scales have separated in the flower buds), infection risk is limited.  For those of you with later varieties/blocks, particularly to the North of the Valley, your plants may not have reached F2 given the late season.

To determine whether a planting has buds that have reached 40-50% F2, follow this protocol for floral bud evaluation in Blog Post #5.  

If you have not protected against monilinia blight within the last 7-10 days I would suggest that you do so at your next opportunity. Keep in mind that the propiconazoles (e.g. Pivot, Bumper, Tilt, Mission, Fitness, and Propi Super) with back action can only be sprayed a total of 2 times per season, so plan your sprays appropriately.

As a reminder, these recommendations are based on conditions observed in the Annapolis Valley, Nova Scotia and may not be applicable to your location. The decision to treat should be based on appropriate conditions observed on your farm and in particular fields/blocks. For detailed information please check out Perennia's Management of Mummy Berry Disease in Highbush Blueberry. 

A complete list of registered products can be found in Perennia's Highbush Blueberry Disease and Insect Management Guide.