W.O. Cline, Extension Plant Pathology
Mummy berry, a disease caused by the fungus Monilinia vaccinii-corymbosi, is an important pathogen in many blueberry-growing regions of the US. Infected berries are unsightly and unmarketable, and severely infested fields can suffer heavy yield losses. In addition to fruit infection, severe blighting of emerging leaf shoots and flower clusters can occur on susceptible cultivars. The name of the disease comes from the shriveled, pale appearance of infected fruit.
Symptoms and Disease Development
The disease overwinters via hard, berry-shaped fungal structures that formed inside infected berries the previous year. Surviving on the ground underneath the bushes, these remants (mummies) are the initial source of re-infection. In early spring, small cup-shaped "mushrooms", spore-bearing structures called apothecia (figure 1) are produced from overwintering mummies. In southeastern North Carolina, mummies break dormancy in February and develop mature apothecia about one month later, when blueberry leaf shoots are emerging. 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 (figure 2), 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 they infect developing fruit while it is still in the flower stage. Prior to harvest, infected berries (figure 3) become light cream-color rather than normal blue and drop to the ground. These infected fruit, if left on the ground, overwinter and provide a source of disease for the following year.
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 disease-free plants to avoid introducing mummies or infected leaf shoots into the new planting.Fungicidal control has proven very successful. Fungicides are used at leaf emergence to prevent primary (leaf shoot) infection, and again during bloom to prevent secondary (flower) infection. Since fungicide labels and recommendations may change, consult your local cooperative extension office, product labels or the blueberry spray schedule in the NC Ag Chem Manual for current recommendations. Sanitation can be used to reduce the incidence and severity of disease, by removing or burying the overwintering mummies. Hand raking or the use of a leaf blower around bushes can be used to move mummies to the row middles where they can be disked under or destroyed. Mummies buried at depths of an inch or more are not able to grow to the surface and are thus prevented from producing spores. Resistance is the ability of the plant to withstand, or resist, infection by a pathogen. All blueberry cultivars appear to be susceptible to mummy berry to some degree. Highly susceptible cultivars include Tifblue, Blueridge, Croatan, Jubilee, and Jersey.
South Region Small Fruit ConsortiumNC Ag Chemicals Manual Horticulture Information Leaflets (HIL) Home PageSmall Fruit Information for North CarolinaNorth Carolina Insect NotesNCCES Educational Resources
For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.**October 2010