Mummy berry disease

Monilia vaccinii-corymbosi is a fungal pathogen belonging to the genus Monilinia, which is primarily responsible for the disease known as "mummy berry" in highbush blueberries (Vaccinium corymbosum). It is a highly specialized fungus that poses a significant threat to commercial blueberry production worldwide.

The disease cycle is characterized by two distinct phases of infection. In early spring, ascospores released from overwintering structures infect young shoots, leaves, and flowers, causing a condition known as "blight" or "shoot strike." Later in the season, the fungus colonizes the developing fruit, causing them to shrivel, harden, and turn tan or gray, eventually becoming mummified sclerotia.

The biology of the fungus is strictly dependent on the host phenology. The pathogen overwinters as sclerotia (mummies) buried in the soil or leaf litter. During early spring, these mummies produce cup-shaped fruiting bodies called apothecia. These structures discharge ascospores that travel via wind currents to infect the emerging green tissues of the blueberry plants.

Optimal conditions for infection include cool, wet weather coinciding with the bud break and early flowering stages of the blueberry plant. Humidity is the key environmental driver, as it facilitates both the development of apothecia and the germination of spores on the susceptible host tissues. If these conditions persist, the pathogen can spread rapidly through an entire field.

The economic impact of the mummy berry pathogen is severe, resulting in direct crop loss due to fruit mummification and long-term reduction in bush vigor due to shoot blight. Effective management strategies include:

• Sanitation by removing and destroying infected shoots and mummified berries.
• Applying a layer of mulch (wood chips or sawdust) to cover the mummies and prevent spore release.
• Careful cultivation to bury infected plant debris deeper into the soil.
• Timely application of systemic and contact fungicides during the critical spring infection window.