Mummy berry is not a seasonal breakfast cereal. Instead, it is a fungal disease of blueberries.
The Monilinia vaccinii-corymbosi fungus is nearly always present in the soil. And a cool, wet spring can set the stage for crop losses.
Symptoms of mummy berry
A healthy summer blueberry bush is thick with leaves, twigs, blossoms, and fruit. After a cool, wet spring, you may notice that some of the blueberries shrivel up, turning hard and gray. Before the fruit even appears, you may see a coating of brown or blue spores on the veins of infected leaves. You may also see drooping, wilting, brownish flower clusters that are turned in on themselves before they turn brown and die. Immature fruit falls to the ground, and twig tips become blighted in a condition called shoot strikes and die. These are all symptoms of mummy berry.
Mummy berry life cycle
Tiny cup-like mushrooms (apothecia), also known as trumpets, growing around the base of your blueberry bushes at budbreak often indicate mummy berry. These mushrooms emerge when temperatures range from 50 to 57°F, so check your thermometer regularly in spring. As the cup openings of these fungi reach a diameter of 2mm, they can start infecting your plants.
A week or so after budbreak, new vegetative shoots emerge. In both cases, this tender new tissue is vulnerable to infection. The mummy berry mushroom spews fungal spores into the air. Spores land on all this new plant tissue. Pollinators, wind, and water may also carry spores to your blueberry bushes. Once the fungi reach your blueberries, they need adequate moisture to grow. The longer they stay wet, the faster they grow.
Cut open an infected green berry to see white fungal tissue. Afterward, sanitize your cutting tools with a household cleaner to prevent spreading the infection further.
Controlling mummy berry
Once infection occurs, remove any diseased tissue and throw it in the trash. You can reduce the chance of mummy berry causing too much damage in your garden with these tips:
Resistant blueberry varieties
Some blueberry varieties are more resistant to mummy berry than others. According to the USDA Agricultural Research Service, low bush varieties with less than 3% mummified berries include:
A mummy berry-resistant group of varietals called half-highs are crosses between low and high bush varieties. These include Chippewa, North Country, Northsky, and St. Cloud.
Resistant highbush cultivars that rated the best with 10.3% or less mummified berries include the following:
However, high bush varietals are generally not recommended for warmer regions. They need more chill hours than those areas get. A cross between a southern highbush and rabbiteye blueberry, called Pearl River, is resistant to mummy berry. Berkeley variety seems to be the most vulnerable to mummy berry infection.
To enjoy the lush, sweet flavor of blueberries in summer, install the most resistant variety suitable to your microclimate.
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