Mummy Berry Post #3 2021: May 6, 2021

 

A quick update on Mummy Berry Development

 

Floral bud counts on May 05, 2021 from the Annapolis Valley Nova Scotia:

 

Early variety with 98% floral buds well advanced beyond the F2 stage (Figure 1).

Figure 1. Floral buds of an earlier variety well advance than F2 stage.

Significant floral bud development was observed for Duke (mid maturity variety) with 40% buds at F2 stage (Figure 2). 

Figure 2. Floral buds of Duke (mid maturity variety).

 Whereas for Burlington (late variety) 25% of floral buds were at F2 stage (Figure 3).  

Figure 3. Floral buds of Burlington (late maturity variety).

Many mature apothecial cups of Mummy berry were observed which are releasing ascospores (Figures 4 and 5).

 

Figure 4 and 5. Mature apothecial cups.

Given the rain last night predicted rain through the week-end, along with warmer weather, the conditions will be conducive to disease establishment with high risk of infection for early to mid maturity varieties.  

Staging Your Blueberries:

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 2 above). 

Based on the wetness period and different air temperatures, Paul Hildebrand and Rick Delbridge developed the Mummy Berry Forecast System in Nova Scotia (Table 1). By visually assessing when the floral bud scales have separated and leaf buds are more than 0.6 cm green, growers can determine when 40-50% bud break has occurred. If temperature and leaf wetness fall within the moderate to high infection range on the table, it is recommended that the grower apply a fungicide within 72 h from the start of the wet period.

Table 1. Temperature and wetness conditions required for Mummy Berry infection. 

 Correct timing of the first spray is critically important for good control. Treatments should not be considered until greater than 40% of the buds are past the F2/V2 stage.  There is no need to spray if you have no history of mummy berry disease on your farm.

 In preparation for an infection period, make sure you have product on-hand.

Products with the active ingredient propiconozole (Pivot, Bumper, Tilt, Mission, Fitness, and Propi Super) can be applied after an infection event, providing up to 72 hour ‘back action’, in addition to being excellent protectants against future infections for 7-10 days after application. Quilt is listed as a preventative fungicide, but also displays systemic and curative properties.

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

As a reminder, these recommendations are based on conditions observed in the Annapolis Valley, Nova Scotia and may not be applicable to your location. Infection periods only occur when bud development has reached the F2 stage, monilinia apothecial cups are present, and temperature and moisture levels are ideal.