Mummy Berry Post #2 2021: April 29, 2021

A quick update on Mummy Berry Development: 

Floral bud counts on April 28, 2021 from the Annapolis Valley Nova Scotia.

Early variety with 45% buds at F2 stage (Figure 1). 

Figure 1: Buds of early varieties at top of branches are open at the F2 stage

Whereas, buds of Burlington and Duke still largely have not advanced to the F2 stage of maturity.  These varieties are only showing 5% or less of the buds at the F2 stage (Figure 2). 

 

Figure 2: Buds of mid to late maturing varieties are still tight and have not advance to the F2 stage

Some of the apothecia are mature and can release ascospores (Figures 3 and 4).

 

Figures 3,4: Development of the Apothecia: some apothecia in Figure 4 are flat and capable of ascospore release

Given the anticipated rain and warmer weather expected this weekend, there is a risk of an infection for earlier fields and varieties.

Based on the wetness period and different air temperatures, Paul Hildebrand and Rick Delbridge developed the Mummy Berry Forecast System in Nova Scotia (Figure 5). 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.

Figure 5: Mummy Berry Forecast System in Nova Scotia

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 and there is no need to spray if you have no history of mummy berry disease on your farm.

If you are below 40% at the F2 stage, it is too early to spray!

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.