Bacteria

There are only 4 types of pathogenic bacteria that cause diseases in cannabis plants.

  1. Bacteria blight

Pseudomonas syringaeCause or pathogen: Pseudomonas syringae pv. cannabina and Striatura ulcerosa

Description and Symptoms:

This is the most common problem. Symptoms resemble the fungal disease – brown leaf spot. It was described on fiber hemp in Europe.

It prefers wet, cool conditions—optimum temperatures for disease tend to be around 12–25 °C (53-77 F). The bacteria is spread with the seeds and dispersed between plants by rain.

Recommendations: Fixed copper compounds (such as bordeaux and copper hydroxide), streptomycin (an antibiotic), and coordination productions (such as Bravo CM) are registered and have been used to control Pseudomonas syringae with various degrees of success. [1,2,3]

  1. Uncommon bacterial diseases

Cause or pathogen: crown gall by Agrobacterium tumefaciens, bacterial wilt by Erwinia tracheiphila, xanthomonas leaf spot by Xanthomonas campestris pv. Cannabis

Description and Symptoms:

Agrobacterium tumefaciensAgrobacterium tumefaciens causes tumors on different plant parts. Crown gall manifests itself initially as small swellings on the root or stem near the soil line, and occasionally on aerial portions of the plant. Additional symptoms include stunting and chlorotic leaves. [4,5]

 

Erwinia tracheiphila – Bacterial wilt first appears as a drooping or wilting of one or a few leaves on the plant, followed by the wilting of the entire plant, then the remainder of the plant wilts, dies, and dries up. In some plants instead of rapid wilting, it causes stunted growth and/or excessive blossoming and branching. [6]

 

Xanthomonas campestris prefers temperature at 25-30 C (77-85 F) and inactive at temperatures below 10 C (50 F). They can live in a soil for over a year and spread through any movement of water including rain, irrigation and surface water. Spraying healthy plants with copper fungicides may reduce the spread of the bacteria in the field.

It causes “black rot” – black lesions on the plant surface. [7]

 

Recommendations: There are some limited chemical control methods that could be used.

 

Sources

1. A review of Cannabis Diseases

2. Pseudomonas syringae 

3. Diseases Caused by Pseudomonas syringae

4. Agrobacterium tumefaciens

5. Agrobacterium tumefaciens, North Carolina State University

6. Erwinia tracheiphila, University of Hawaii

7. Xanthomonas campestris, MicrobeWiki

 

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