Oak acorn rot

The disease known as acorn rot is caused by the ascomycete fungus Ciboria batschiana. This pathogen is a significant threat to oak silviculture as it specifically targets acorns, leading to the development of mummified fruits that are completely incapable of germination.

The primary hosts of this fungus are various species of oak, particularly the common oak and sessile oak. The infection causes substantial economic loss, as it reduces the viability of seeds collected for nurseries and natural forest regeneration efforts globally.

Key symptoms include the appearance of dark, sunken lesions on the acorn surface. These spots expand rapidly, eventually causing the entire internal kernel to turn dark and soft. In the final stages, the acorn becomes hard, shriveled, and turns into a dark sclerotium, which remains dormant until the following spring.

The development of Ciboria batschiana is heavily dependent on moisture and humidity. Excessive rainfall during the acorn development and ripening stages facilitates spore dispersal. The fungus typically overwinters in the forest soil as sclerotia, which produce apothecia that release spores during the flowering period of the host tree.

• Regular collection of healthy acorns from the canopy before they reach the ground.
• Proper post-harvest drying to reduce surface moisture.
• Storage at low, constant temperatures and controlled humidity.
• Fungicidal treatment of acorns intended for planting or storage.

Proactive forest management is essential for minimizing losses. By removing infected acorns from seed lots and maintaining hygienic storage conditions, foresters can significantly curb the spread of this pathogen and ensure higher success rates for future oak plantations.