Mummies are not just for Halloween. Well actually Mummy Berries aren’t! Mummy berry disease is pretty scary. In 2022 the production value of blueberries in our state was approximately $69.7 million. Mummy berry disease, caused by the fungal pathogen Monilinia vaccinii-corymbosi, is one of the most economically important diseases of blueberries. If left untreated, crop damage as high as 50 percent can occur during normal growing seasons. That’s a significant financial blow to this popular crop. Our home gardens are not immune to it either.

While blueberries are one of the most popular backyard fruits because they require relatively low maintenance compared to other fruit species, mummy berry disease is likely the most common disease of blueberries in North America. Its severity varies greatly from year to year depending on weather conditions.

As the name implies, the ripening berry develops a dry, shriveled appearance, then drops from the bush as a result of this disease infection. The berries have a pinkish rather than blue color as the clusters ripen. This fungus can overwinter inside the fallen infected berry, remaining viable for several years. Some blueberry varieties are more susceptible than others.

A cool, wet spring combined with late freezes sets the stage for this fungus to get established, and it is a vicious cycle.

Apothecia (mushrooms!) grow in the spring that look like little cups, but can hide in debris around the plants. When the spores are released from the infected berries on the ground the wind spreads them to nearby plants where they will infect beginning shoots and leaves. This causes sudden wilting to the plant – from the leaves and buds to the stem tips and flower clusters. As the infection gains momentum brown necrosis sets in followed by powdery masses of sporulation from the infected parts. From there the secondary spore growth is carried to open flowers along with pollen, often spread by pollinators visiting from one bloom to the next so that the infection makes it into the developing berry through the fruit ovaries.

Most of the time we don’t notice the problem until it’s time to harvest that season’s berry crop but by then it’s too late. If the infection has hit the berry plantings, expect it to erupt again the following year unless action is taken.

A few well-timed applications of the appropriate fungicide early in the growing season soon after bud break can make a real difference if it’s combined with diligent sanitation practices in the fall. Burying mummies helps to prevent primary infections. Rake mummies into the row centers between the plants and bury them at least 1” deep. Use caution: excessive amounts of dirt mounded on top of blueberry roots and stems can result in injury or plant death. This material can also be raked up and hauled away from the fields.

Scout your plants this time of year diligently so you can make sure to break the cycle of disease. If mummy berry disease is present, appropriate fungicides are very important in pre-bloom sprays (for cultivars or seasons in which leaf bud break occurs before flower bud break). Start spraying when green tip occurs on the leaf buds or 1-5% open bloom occurs on the flower buds, whichever comes first. Continue sprays until all blooms have fallen.

Article updated from 2011 Article by Minda Daughtry, Horticulture Agent in Lee County at the time.

Amanda Wilkins Bratcher is the Horticulture Agent for North Carolina Cooperative Extension in Lee County.