Today I want to cover a current disease in blueberries. It is called Mummyberry. Mummyberry is probably the most commonly known disease of blueberry. It is caused by a fungus that infects both young growing shoots and the fruit. The death of new shoots really 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.

Shoot blight is the first symptom seen after dormancy has broken. Blighted shoots are the result of infection of emerging leaf buds. A Christmas tree pattern of dead tissue begins forming at the base of the leaf. 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. Spores that form on the blighted shoots infect the blossoms as they open. The spores are carried by pollinating insects or by the wind to the open flowers. The blighted shoots are attractive to bees and the spores are in a sweet matrix so bees and other insects will visit the shoot strike and carry the spores to open flowers.

Evidence of blossom infection does not appear until the fruit begins to ripen. As normal berries ripen, the infected berries begin to shrivel and turn a pinkish color. These "mummy-berries," are filled with the fungus. They fall to the ground, shrivel, and turn dark brown or black becoming pumpkin-shaped. They serve as an inoculum source the following spring. Crop losses of 30 to 40% are experienced where no fungicide control is practiced.

That is all for today, this has been Al Gaus for Michigan State University Extension in Berrien County.