MUMMY BERRY DISEASE OF BLUEBERRY

 

Mummy berry caused by Monilinia vaccinii-corymbosi is a fungal disease of major importance in the northern and southern highbush blueberry regions, where it causes considerable damage to the fruit. In addition, severe blighting of the leaves, shoots, and flower buds of rabbiteye cultivars Delite, Southland, Premier and Tifblue has occurred in North Carolina plantings.

Illustrations:

  • Blueberry fruit infected with the mummy berry fungus.
  • Cup-shaped apothecia are fruiting bodies of the fungus.
  • Close-up of primary infection stage.
  • Blueberry stem with severe damage from primary infection stage.

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    Symptoms and Disease Development


    In early spring, small cup-shaped spore-bearing structures called apothecia are produced from sclerotia. In southeastern North Carolina, overwintered sclerotia break dormancy around the first week in February and develop mature apothecia about one month later. Spores (ascospores) produced by the apothecia are liberated during cool, wet weather and are carried by air currents to the young emerging leaf and flower shoots. These spores infect and blight the young shoots, and secondary spores (conidia) are produced in great abundance on the blighted leaves. These conidia are carried by wind or insects to open flowers where the ovaries become infected. Prior to harvest, infected berries become light cream-color rather than normal blue and drop to the ground. These infected fruit, if left on the ground, form overwintering sclerotia and provide a source of disease the following year.

     

    CONTROL


    Avoidance can be used by anyone who is producing blueberries in an isolated location. Unless the disease is present in wild or cultivated bushes nearby, growers and homeowners can successfully avoid mummy berry by planting only dormant (leafless) bare-rooted plants. This avoids introducing sclerotia or infected leaf shoots into the new planting. If a new planting is established with potted plants, rake off and destroy any plant debris on the surface of the soil in the pot to prevent planting of sclerotia along with the new bush. This is especially important with plants purchased from other states, since new species or races of mummy berry might be introduced into NC as sclerotia in pots.

    Fungicidal control, especially the use of triforine (Funginex) has proven very successful. Benomyl (Benlate) is also used in bloom to prevent secondary infection. Consult product labels or the blueberry spray schedule in the NC Ag Chem Manual for specifics.

    Sanitation was the traditional means of controlling this disease for many years. Growers hand-raked fields to remove overwintering sclerotia (mummies). While raking is no longer practical on a large commercial scale, growers can still reduce disease by disking to bury sclerotia and by clean cultivation. Burying mummies at depths of one inch or more will help to prevent germination.

    Resistance All highbush cultivars appear to be susceptible to the mummy berry phase to some degree. Some of the most resistant cultivars are among the newly released southern highbush types (Bladen, Reveille). Note that the fruit infection stage of mummy berry has not been observed to occur on rabbiteye blueberry (Vaccinium ashei) in NC. This means that growers in the piedmont of NC may be able to avoid mummy berry by planting only this species, as they typically do. Rabbiteye blueberries DO get fruit infections in Georgia and Mississippi, perhaps indicating the existence of another species or race of the mummy berry fungus in those areas.

    Last updated: 27 May 1997
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