Fruit
IPM Fact Sheet Fruit
IPM Fact Sheet
Mummyberry:
Mummyberry is probably the most commonly known disease of blueberry. It
is caused by the fungus Monilinia vacinii-corymbosi. This disease infects both
young growing shoots and the fruit. The death of new shoots reduces the yield potential
for many years to come. But most growers in Michigan are more concerned about the loss of
fruit from fruit infections.
Symptoms
Shoot blight is the first symptom seen after dormancy has broken Blighted shoots
are the result of ascospore infection of emerging leaf buds. A blighted vegetative shoot
is visible to the right. A Christmas tree pattern of dead tissue forms from the base of
the leave following the leaf veins. Eventually the whole growing point and current
season's growth will die. Death of the growing points and loss to the fruit that might
have formed on the shoot is a major concern but most growers do not factor this loss in
unless there is a lot of shoot strikes in a field. Conidiospores form on the blighted
shoots. These conidiospores infect the blossoms as they open. The spores are carried by
pollentaing insects or by the wind to the open flowers.
Evidence of blossom infection does not appear until the fruit begins to ripen.
The infection lays dormant until the berry begins to ripen. As normal berries ripen, the
infected berries begin to shrivel and turn a pinkish color These
"mummyberries," are filled with pathogenic fungus. They fall to the ground,
shrivel, turn dark brown or black becoming pumpkin-shaped. They serve as an inoculum
source the following spring when apothecia form and disease cycle begins again. Crop
losses of 30 to 40% are experienced where no fungicidal control is practiced. This loss of
the current seasons crop in the main loss suffered by Michigan Blueberry Growers. There is
some varietal resistance, but it is not an effective disease control strategy.
Disease Cycle: The fungus has a complex life cycle. The
disease infects blueberries twice. It infects the new shoots with ascospores from the
overwintering apothecium. The infected shoots then infect the flowers. The disease
overwinter in a psuedoscloratia called mummies, formed from the infected fruit. Ascospores
of the fungus are dispersed from mushroom-like apothecia that form on last year's
mummyberries which overwinter on and in the soil under the bushes. The mushrooms emerge at
the same time as the buds of the blueberry bush begin to open. Spores are dispersed from
the mushroom as it matures. There is some argument over whether or not a hard killing
freeze will kill the mushrooms and the spores. There is little doubt that freeze damaged
tissues are more susceptible to infection.
The blighted shoots are attractive to bees and the conidiospores are in a sweet matrix so bees and other insects will visit the flower and carry the mummy berry spores to open flowers.
Begin appling fungicides when green tissue is exposed
Control: Chemicals applied to the soil do not effectively destroy apothecia. Applying fungicides to the bushes prebloom and during bloom can give excellent control. Refer to the MSU Michigan Fruit Management Handbook, (Extension Bulletin E-154) for fungicides, rates and timing.
There is an good article on Mummy berry in the April
15, 2003 Fruit CAT Alert.
Another article on Monitoring for Mummy berry in
blueberries appeared in April of 2004
In 2005, MSU created a Michigan Blueberry Facts website.
Check the Blueberry Page at this site and the Michigan Fruit Team Blueberry page for other postings
