Appearance

• Botrytis rot also goes by the name Botrytis blight. Gray mold disease is the common name for this fungal condition. Botrytis rot may first appear as tiny black spots along the surface of the leaves and fruit skins. These raised black spots are the fruiting bodies of the fungus. As the disease progresses, the citrus fruits develop water-soaked lesions. Fruits that recover from Botrytis rot may have scarring, while fruits that succumb to this disease develop soft, mushy spots as they decay.
  
  

Risk Factors

• Botrytis rot is most common in areas that experience cool, moist weather, such as coastal growing areas. Prolonged periods of cool, damp weather provide the optimal conditions for the growth and reproduction of Botrytis spores. Lemon trees are more likely to suffer from Botrytis rot than other varieties of citrus fruits. Improper spacing of citrus trees may lead to crowding, a condition that promotes the growth of fungal diseases.
  
  

Prevention

• Reducing the risk of Botrytis rot in citrus trees requires minimizing the factors that promote the growth of the fungal spores. Proper pruning can help promote good airflow around the branches and developing fruits, while growing citrus trees in an open, sunny location with exposure to breezes can also help. Raking up fallen fruit and leaves before they start to decompose can also help reduce the risk of fungal diseases and bacterial disorders in citrus trees.
  
  

Treatment

• The University of California recommends treating citrus trees prior to expected foggy or rainy weather, using a fungicide that contains benzimidazole or copper. Although this can help reduce the growth and reproduction of Botrytis spores, it may be unfeasible and difficult during unseasonably wet cycles. Treating the fruits after harvesting may be necessary to prevent decaying and rotting during storage.