Cercospora spp. in Cannabis: Etiology, Symptoms, and Management

The genus Cercospora groups phytopathogenic fungi responsible for leaf spots in numerous crops, including Cannabis sativa. Although its incidence in cannabis has been less documented than in other crops, its presence can significantly affect photosynthesis and yield, especially in favorable environmental conditions.

Cercospora spp  are ascomycete fungi that produce elongated and septate conidia. They develop mainly under conditions of:

• High relative humidity (>80%)

• Moderate temperatures (20–30 °C)

• Low ventilation in dense crops or under greenhouse

  
  

The pathogen survives in infected plant residues and is dispersed by splashing water, wind, or contaminated tools.

In cannabis, Cercospora infection  manifests itself mainly in mature leaves:

• Circular to irregular brown to gray spots

• Well-defined dark edges (necrotic halo)

• Clearer center of the lesion, sometimes ashy

• Coalescence of spots in severe infections

• Premature senescence of leaves

These symptoms can be mistaken for nutritional deficiencies or infections by other fungi, so microscopic diagnosis is recommended.

Integrated management

1. Cultural management

• Disposal of infected plant residues

• Adequate spacing between plants

• Improved ventilation and reduced leaf moisture

• Watering directed at the soil (avoid wetting the foliage)

  
  

2. Monitoring

• Regular inspections, especially in advanced vegetative stages

• Early Identification of Symptoms

  
  

  

  
  

3. Biological control

• Use of antagonists such as Trichoderma spp. (depending on local availability)

  
  

4. Chemical Control (where permitted)

• Application of authorised protective or systemic fungicides

• Rotation of active ingredients to avoid resistance

  
  

Although Cercospora is not one of the most reported pathogens in cannabis, its potential impact in favorable conditions makes it necessary to recognize it early and preventively manage. The implementation of appropriate agronomic practices is key to reducing its incidence and preserving crop productivity.