Blueberry Mummy Berry is caused by the fungus Monilinia vaccinii-corymbosi, and is a major disease of blueberries in various producing regions. The fungus overwinters on mummified fruit on the ground. Fungal fruiting cups called apothecia produce sexual spores ( called ascospores), which are discharged and moved by the wind to infect young developing foliage and fruit. To help control this disease, researchers have developed the Mummy Berry Infection Season Growing Degree Day Model to track ascopore maturation and dispersion, based on local weather factors.

Calculating Growing Degree Days

The Mummy Berry growing degree model uses a lower threshold of 32F and an upper threshold of 80F. It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field. The “biofix” date, or date from which to start accumulating growing degree days, should be set at January 1st, for the Northern Hemisphere After this, average first ascopore release will occur at 1020 GDD (F) and the average last ascopore release at 1498 GDD (F). This window is the optimum time for fungicide treatment.

Source:

Hildebrand, P.D. and P.G. Braun. 1991. Factors affecting infection of lowbush blueberry by ascospores of Monilinia vaccinii-corymbosi. Can. J. Plant Pathol. 13:232-240., Ramsdell, D.C., J.W. Nelson and R. Myers. 1974. Phytopathology 64:222-228 An Epidemiological Study of Mummy Berry Disease of Highbush Blueberry,