Phomopsis dieback of tea

Diaporthe theae is a pathogenic fungus responsible for Phomopsis dieback, a debilitating disease affecting tea plants (Camellia sinensis). This fungal disease primarily attacks the woody stems and branches of the bush, disrupting nutrient flow and causing necrosis. It is recognized as a significant threat to tea cultivation, particularly in regions with high humidity and intensive tea production.

The primary host for this pathogen is the tea plant. While healthy plants can sometimes resist minor infections, those weakened by environmental stress, frost, or improper pruning techniques are highly susceptible. The fungus typically invades through open wounds on the bark, making maintenance practices a critical factor in the disease's entry and establishment.

The symptoms of the disease are characterized by the appearance of sunken, darkened lesions on stems. As the infection progresses, these lesions expand and girdle the branch, leading to chlorosis, wilting, and the eventual death of the affected parts. Upon close inspection, the surface of the dead bark may reveal small, black reproductive structures known as pycnidia, which indicate the presence of the pathogen.

Development and spread of Diaporthe theae are strongly correlated with favorable climatic conditions, specifically high humidity, frequent fog, and moderate temperatures. Wind and splashing rain facilitate the dispersal of spores from diseased branches to healthy ones or to neighboring bushes. Improperly pruned branches left on the ground serve as a reservoir for the fungus, perpetuating the cycle of infection year after year.

The economic impact of Phomopsis dieback is significant due to the loss of productive branches and the potential for cumulative death of the tea bushes. To mitigate these risks, growers should adopt integrated pest management strategies:

• Implement strict sanitary pruning to remove and destroy all infected plant material.
• Sterilize pruning tools between bushes to prevent cross-contamination.
• Improve air circulation within the canopy through balanced pruning and spacing.
• Apply preventative fungicides specifically targeting the pathogen during peak risk periods.
• Monitor plantations closely during wet, warm weather to detect early symptoms of dieback.