WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Mummyberry

(Monilinia vaccinii-corymbosi)

Diseases

 

Mummyberry

 

Symptoms

Mummyberry can cause yield losses of up to 50% in the Pacific Northwest when conditions are correct; it infects shoots, flowers, and fruit. Mummyberry affects growing tips, foliage and fruit. Fruit infection results in unmarketable fruit. In early spring, a mushroom-like spore cup is seen on the ground, emerging from fallen infected berries. Infected flower buds and stems turn brown and black. Infected foliage wilts and turns brown. Infected fruit shrivels and appears mummified as it develops; these fruit appear to ‘ripen’ earlier than uninfected fruit. Mummyberries drop to the soil.

 

Mummyberry

 

Life History

Mummyberry is a fungus that overwinters in the previous year’s berries that have fallen to the mulch and soil. In early March or late February, a very small mushroom-like spore cup emerges from the infected berry. Spores are released from the fruiting body usually when bud swell begins and green tissue is present. Spores are spread via wind currents.

Early season infection of flower buds and stems is promoted by wet conditions, with leaf wetness lasting six to twelve hours. After the initial infection, the mummyberry fungus produces a second type of dispersal (conidia) in the form of grey-green tufts. Conidia are dispersed through wind, water splashes and insect pollinators.

Conidia dispersed to flowers cause fruit to shrivel and mummify as the fruit develops. As the fruit mummifies, the berry drops to the soil to overwinter.

 

Mummyberry

 

Monitoring

In areas with a history of mummyberry, increase scouting locations throughout the field.  Begin monitoring for mummyberry in February and March. Scrutinize the soil at the base of 20 blueberry bushes per site. Rake the soil and look for fallen berries. Open berries and look for the developing spore cup. The developing spore cup will appear much like a germinating seed with the terminal end orienting towards the soil line. In March, begin monitoring for the mushroom-like spore cups using the same scouting method. Peak spore production from the spore cups will usually occur a couple of weeks after bud break.

Once green foliage develops, scout for conidial masses produced from the primary infection. On the plant the first symptom is shoot blight, browning along the major veins. Leaves wilt quickly and twig tips will bend resembling shepherd’s crook. Look for grayish green tufts of fungus associated with wilted foliage and blackened stems. Secondary infection from conidia can occur throughout bloom.

Upon fruit set, regularly inspect fruit clusters for discolored fruit. Record the percent of mummyberry infect in order to assess effectiveness of management practices.


Mummyberry

 

Thresholds and Management

Detection of mummyberry in a field is the threshold for treatment.

Prevention of mummyberry establishment is key for managing the disease. After harvest, and if possible, clean up dropped fruit. Prior to bud break, shallow cultivation, no deeper than one inch, underneath bushes will prevent spore cup development. Mummies can be covered with soil or mulch at least two inches (5 cm) thick. Avoid wet sites and overhead irrigation at least until petal fall and try to improve drainage. Choose late-blooming and resistant cultivars if possible. Consider beginning fungicide applications at bud break to protect green tissue from primary infection. Number of fungicide applications will be determined by the degree of risk. Consider strict fungicide regimes if disease pressure is high or spore cups are found at 10-20% of the bushes and weather conditions are wet and above 50°F.

Prevention of primary infection by mummyberry is paramount for managing the disease. Many environmental factors can contribute to the degree of infection, such as weather, prevailing winds and neighboring fields. These factors along with cultural management and monitoring information should be considered in implementing a fungicide program.

 

Mummyberry

 

Resources

Michigan State University, Michigan Blueberry Facts, Mummyberry
http://www.blueberries.msu.edu/mummyberryguide.html

Michigan State University Extension, Mummyberry Factsheet
http://web1.msue.msu.edu/vanburen/fmummy.htm

Michigan State University Extension, Blueberry Fruit Rot Identification Guide
http://web2.msue.msu.edu/bulletins/Bulletin/PDF/E2847.pdf

Oregon State University Extension, An Online Guide to Plant Disease Control, Blueberry-Mummyberry
http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=182

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu