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Mummy Berry of Blueberry

by Michael A. Ellis    

Mummy berry is one of the most serious diseases of blueberry. Once the disease becomes established in a planting, it can destroy most of the crop. Losses result from:

1. rotted berries; and
2. killing or blighting of blossoms, blossom and leaf clusters and young shoots.

Symptoms

Blighting of new shoot tips and blossoms can be easily mistaken for frost damage. By blossom time, the infected young leaf and shoot growth will wilt, turn brown and die. About a week or so after infection of the early new growth occurs, dead areas develop on the petioles and along the midrib and veins of the leaves or at the base of flowers. Berries that develop from infected flowers may attain nearly full size before turning tan or gray and shriveling into hard mummies, which drop to the ground at or before harvest.

Causal Organism

Mummy berry is caused by the fungus, Monilinia vaccinii-corymbosi. The fungus overwinters in the shriveled mummies on the ground. In early spring, cup- or globe-shaped structures of the fungus called apothecia are produced on mummified berries during cool rainy periods. Spores produced inside apothecia are released into the air and carried by the wind to young developing leaf shoots and flowers where they cause primary infections. If moisture is not present, the fungus will not produce spores. However, the fungus may survive in mummies for one year or more. Another type of fungus spores (conidia) is produced on dead tissue that results from primary infections. These conidia are spread during bloom by wind and insects, and result in secondary infection of flowers. Fruit that develops from infected flowers turns into mummies and falls to the ground.

Control

Removing mummified berries from the planting will greatly aid in controlling the disease. Removing these berries is not practical on a commercial scale, but may be of value in backyard plantings where there are just a few plants. After removing mummies, burn or bury them.

Cultivation in early spring to disturb or cover the mummies has been reported to be effective. Mummies that are disturbed or covered with soil at this time remain dormant or do not produce spores. Cultivation between rows and raking under plants to disturb or cover mummies should be done as early as possible in the spring and repeated after each hard rain until after bloom. If just a few mummies are missed, they can produce enough spores to infect the planting.

Where mummy berry is a problem, a good fungicide spray program is essential.

For the most current spray recommendations, commercial growers are referred to Bulletin 506-B2 "Ohio Commercial Small Fruit Spray Guide," and backyard growers are referred to Bulletin 780 "Controlling Diseases and Insects in Home Fruit Plantings." These publications can be obtained from your county Extension agent or the Extension Publications Office, The Ohio State University, 385 Kottman Hall, 2021 Coffey Road, Columbus, OH 43210-1044.

Figure 2. Disease cycle of mummy berry. We wish to thank the New York State Agricultural Experiment Station for use of this figure. Taken from Small Fruit Crop IPM Disease Identification Sheet No. 3.