Blanching of hazelnut

Blanching in hazelnuts is a widespread condition characterized by the degradation of the kernel quality. While sometimes confused with physiological disorders, it is frequently associated with fungal pathogens (such as Monilinia species) that colonize the kernel inside the shell. The disease compromises the integrity of the nut, turning the kernel mushy or discolored and rendering the produce unmarketable.

The disease primarily affects hazelnut orchards (Corylus avellana). The main symptom is the discoloration and deterioration of the nut kernel, which may appear white, wrinkled, or show signs of fungal mycelium growth upon opening the shell. Often, the presence of the disease is only detected during the cracking and processing phase, causing significant logistical and quality control challenges.

The development of the disease is heavily influenced by environmental conditions, particularly high humidity and heavy rainfall during the nut maturation stage. The spores of the causative fungi are easily dispersed in wet weather and enter the nut through wounds caused by insect pests, such as the hazelnut weevil, or through microscopic cracks in the shell caused by uneven water uptake.

The economic impact of this condition is significant. Affected kernels suffer from rancidity and unpleasant odors, making them unsuitable for confectionery or direct consumption. Furthermore, if high rates of infestation occur, an entire harvest lot may be deemed spoiled, leading to substantial financial losses for growers and processors alike.

Effective management requires an integrated approach. The most critical step is the control of insects, particularly the hazelnut weevil, which creates the entry points for the infection. Orchard sanitation, including the prompt removal of fallen nuts and pruning to improve air circulation, is also vital. Additionally, the strategic use of fungicides during the growing season can help mitigate the risk of infection when conditions favor fungal outbreaks.