Citrus Black Spot Disease Management and Pathogen Dynamics

Citrus Black Spot (CBS) is a globally significant fungal disease caused predominantly by Phyllosticta citricarpa. It manifests as dark lesions on fruit and foliage, leading to pre- and post-harvest losses in major citrus-producing regions. Effective management integrates cultural practices—such as removal of fallen debris and optimised irrigation to reduce leaf wetness—with judicious fungicide applications guided by local weather patterns. Recent advances in genomic and population genetic studies have revealed that multiple Phyllosticta species can co-occur on citrus hosts, exhibiting clonal dispersal and varying levels of pathogenicity. Understanding the spatiotemporal dynamics of inoculum release and infection risk has informed more precise spray schedules and canopy management. Concurrently, exploration of natural resistance traits, endophytic microbial interactions and novel diagnostic tools promises to enhance early detection and reduce reliance on broad-spectrum chemicals. This multidisciplinary approach, combining epidemiology, molecular biology and precision agriculture, is critical to safeguarding yield, minimising environmental impact and maintaining trade compliance in the face of evolving pathogen populations.

Research from Nature Portfolio

Analyses of disease occurrence within commercial groves have demonstrated that CBS-affected trees are non-randomly distributed, supporting the predominance of short-range dispersal of asexual spores. Cluster analyses across seasons revealed persistent foci of infection, indicating that young trees entering their first fruiting cycle can act as amplifiers under heavy disease pressure. Complementary studies have shown that incidence and severity of fruit lesions vary markedly with fruit position in the canopy and microclimatic conditions. Higher infection rates occur on the outside of the canopy and above two metres in height, correlating with prolonged periods of high relative humidity and suitable temperature. Together, these findings have refined models of disease risk and underscored the value of canopy-specific monitoring to optimise fungicide timing and reduce unnecessary applications.

Citrus Black Spot Disease Management and Pathogen Dynamics publication trend

The graph below shows the total number of articles in citrus black spot disease management and pathogen dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Citrus Black Spot (CBS): A disease of citrus fruits and leaves characterized by dark necrotic lesions, primarily caused by Phyllosticta citricarpa.

Conidia: Asexual spores produced by fungi, responsible for short-distance dispersal of inoculum.

Clonal dispersal: The spread of genetically identical pathogen strains, indicating limited sexual recombination.

Canopy microclimate: The specific temperature and humidity conditions within the tree foliage that affect pathogen infection and development.

Fluorescence imaging: A diagnostic technique that uses light-induced emission to visualise pathogen structures or stress responses in plant tissues.

References

1. Detection of citrus black spot fungi Phyllosticta citricarpa & Phyllosticta capitalensis on UV-C fluorescence images using YOLOv8. Smart Agricultural Technology (2024).
2. Identification of Biomarkers Associated with Phyllosticta citricarpa Tolerance. Molecules (2024).
3. Clonal Expansion in Multiple Phyllosticta Species Causing Citrus Black Spot or Similar Symptoms in China. Journal of Fungi (2023).
4. Spatial and Temporal Patterns of Commercial Citrus Trees Affected by Phyllosticta citricarpa in Florida. Scientific Reports (2017).
5. The Effect of Weather and Location of Fruit within the Tree on the Incidence and Severity of Citrus Black Spot on Fruit. Scientific Reports (2020).