As discussed in the previous blog post, the season continues to chug along at a slow pace with buds slowly progressing. On Friday May 8th, Sajid confirmed that the early block of Duke he is monitoring now has 65-72% of floral buds are at F2 (bud scales have separated in the flower buds), as shown in Figure 1. However, in the block of later varieties buds are swollen but not yet susceptible to monilinia blight infection.
Figure 1. Floral buds at F2 stage of development.
That said, mature apothecia cups (Figure 2) have been confirmed, meaning that if we do experience appropriate conditions (see previous blog post) an infection period is possible. Given the cool temperatures we have been experiencing, we are projecting that the season will be prolonged. I would encourage you to stretch out your sprays to 7-10 days and maintain a spray schedule that protects susceptible buds. 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. Mature apothecia 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.
