Mummy Berry 2020 - Post # 7

Wednesday, May 20, 2020

Over the past weekend we expected major progress in floral bud development. As you can see in Figure 1, temperatures from March 01 to May 19, 2020 are still tracking significantly behind the 5- and 10-year averages.

Figure 1. Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to May 19th for the past 17 seasons. Provided by Jeff Franklin (AAFC).

On Tuesday May 19th, Sajid confirmed that the early block of Duke he is monitoring now has 85-95% of floral buds are at F2 (bud scales have separated in the flower buds), as shown in Figure 2. Furthermore, the medium maturity variety has 60-70% of the floral buds at F2 stage (Figure 3). However, in the block of late variety, 35-50% buds are susceptible to Monilinia blight infection (Figure 4). 

Almost all apothecial cups have been matured (Figure 5) and they are drying up. If you already had sprayed once with the propiconazole, there is no need of additional spray at this point as the weather will be dry with no rain forecast for the next one week. If you have not sprayed in the last 7-10 days, it would be a good idea to apply a protectant spay to get you through. Please 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.
Figure 2. Early maturity variety, floral buds at F2 stage of development.

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

 Figure 4. Late maturity variety, floral buds at F2 stage of development.

Figure 5. Mature apothecial cups. 
To determine whether a planting has buds that have reached 40-50% F2, follow this protocol for floral bud evaluation:

In a field, block or variety (whatever area you would spray at one time) walk a zig zag (not only the edge) stopping a total of 5-10 times to count floral buds.  With each stop, count 10-15 floral buds on a stem and use that to guesstimate the floral bud stage on that plant.  Use your 5-10 plant guesstimates to determine the average floral bud stage of the field, block or variety.  Remember, you want to protect any planting that has 40% or higher of floral buds at F2 (Figure 1 above).

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.