Lesson 1, Topic 1
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Understanding transmission methods and symptoms

Cartier April 13, 2023

Cannabis plants, like all living organisms, can be susceptible to various pathogens such as viruses, bacteria, and fungi. These pathogens can cause numerous diseases, reducing yields, poor-quality buds, or even plant death. To protect your cannabis plants from these pathogens, it’s essential to understand their transmission methods and the symptoms they cause. In this article, we will explore the various ways pathogens can spread and the signs of infection to look for in your cannabis plants.

Transmission Methods of Cannabis Plant Pathogens

a. Airborne Transmission:

  • Many fungal spores and some bacteria can be carried by air currents
  • Can spread rapidly, especially in poorly ventilated or overcrowded grow spaces
  • Example: Powdery mildew spores

b. Waterborne Transmission:

  • Pathogens can spread through contaminated water sources or splashing water
  • Ensuring proper water quality and avoiding excessive moisture can reduce the risk
  • Example: Pythium root rot

c. Mechanical Transmission:

  • Pathogens can be transferred via contaminated tools, equipment, or clothing
  • Regular cleaning and sanitizing can prevent the spread of diseases
  • Example: Tobacco mosaic virus (TMV)

d. Insect Vectors:

  • Some pathogens are transmitted by insects feeding on or laying eggs in plants
  • Implementing Integrated Pest Management (IPM) strategies can help control the spread
  • Example: Cannabis cryptic virus transmitted by aphids

e. Soilborne Transmission:

Certain pathogens can persist in soil or growing media and infect plant roots

Proper sterilization of soil and using disease-resistant growing media can reduce the risk

Example: Fusarium wilt

Symptoms of Cannabis Plant Pathogen Infections

a. Leaf Symptoms:

  • Yellowing, curling, or wilting of leaves
  • Necrosis (dead tissue) or chlorosis (yellowing between veins)
  • Mottling, mosaic patterns, or streaking on leaves
  • Example: Tobacco mosaic virus (TMV) causing mottled leaves

b. Stem and Branch Symptoms:

  • Stunted growth, weak or hollow stems
  • Lesions, cankers, or galls on stems or branches
  • Example: Fusarium wilt causing stem lesions and wilting

c. Root Symptoms:

  • Root rot, discolored or slimy roots
  • Stunted root growth, reduced root mass
  • Example: Pythium root rot causing root decay

d. Flower and Bud Symptoms:

  • Poor flower development, malformed buds
  • Bud rot, mold, or mildew on flowers
  • Example: Botrytis cinerea (gray mold) causing bud rot


Understanding the transmission methods and symptoms of cannabis plant pathogens is crucial for maintaining a healthy and productive grow environment. By being aware of the various ways pathogens can spread and the signs of infection, you can take preventive measures and implement prompt treatment strategies to minimize the impact on your plants. Regular inspections, proper sanitation, and the use of disease-resistant growing media and cultivars can further help protect your cannabis plants from the negative effects of these pathogens.

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