British Columbia’s Ministry of Agriculture recently released a fact sheet describing the symptoms and spread of the most common diseases affecting cannabis plants. The list includes Fusarium, Pythium, Powdery Mildew, Botrytis, and Hop Latent Viroid (HLVd). Many of the pathogens cause stunted growth as well as reduced yield and potency. Others, such as pythium can cause plant death.
Needless to say, cultivators should do everything they can to prevent infections and ensure a fruitful harvest. The fact sheet concludes with several recommendations for preventing disease in cannabis plants, including:
- Maintain a clean and sanitary environment
- Maintain proper humidity and temperature
- Treat irrigation water
- Identify and remove diseased plants
- Plant disease-resistant cultivars
- Use disease-free planting stock or cuttings
Maintain a clean and sanitary environment
All the plant pathogens described in the fact sheet can be spread through contaminated equipment, tools, and potentially staff and visitors. That is why maintaining clean and sanitary growing facilities can minimize the potential spread of pathogens.
Tools, equipment, dehumidifiers, air filters, and growing and trimming rooms, should be regularly cleaned and sanitized. Visitors and staff should also use footbaths before entering the growing area and wear hairnets, beard nets, gloves, and Tyvek coveralls.
Furthermore, air filtration and purification systems such as HEPA filters and UV may also be used to reduce airborne contaminants and pathogens. In particular, botrytis and powdery mildew are spread through the air.
Medicinal Genomics offers PathoSEEK Detection Assays that can be used to screen facilities for a variety of bacteria, molds, and pathogens that could infect your facility. Swab any surface (floors, walls, ceilings, ventilation ducts, equipment, drains, hoses, etc.) and run the sample on a qPCR instrument to identify sources of contamination.
Maintain appropriate humidity and air temperature
Certain pathogens, such as powdery mildew and botrytis thrive in warm, humid environments with poor air circulation. Facilities that can control these factors can reduce the severity of infections, should they occur. In the case of botrytis, this is particularly important to monitor these levels in the flowering room because the risk of infection increases as buds mature.
Treat irrigation water
Contaminated water is a primary source of infection for pythium, which creates water-borne spores (zoospores). Treating irrigation water with UV, chlorine, or other registered products may prevent the spread of this pathogen as well as fusarium, which is believed to be responsible for root rot, crown rot, and damping-off.
Identify and remove diseased plants
Removing diseased plants from your facility is the best way to prevent the buildup of inoculum and the spread of disease. DNA-based testing tools, such as our PathoSEEK detection assays, can be used to screen plants for pathogens before they show visual symptoms or to verify a suspected infection.
Plant disease-resistant cultivars
Certain cannabis cultivars have shown resistance to powdery mildew, which would obviously eliminate the risk of that type of infection.
Our team has analyzed genomic data from the 42 cultivars looking for copy number gains and losses among 82 disease resistance genes. We noticed PM-susceptible cultivars had deletions of a thaumatin-like protein (TLP) gene, while PM-resistant cultivars contain copy number gains in the same gene.
Further functional studies need to be performed before definitive markers can be established, but breeders and cultivators can benefit from sequencing their cultivars to look for trends among these genes and breed accordingly.
Use disease-free planting stock or cuttings
Contaminated plant stock is the primary route of infection for fusarium. Cuttings that are taken from a contaminated mother plant will often damp off.
Producers should ensure that any plants entering the growing facility, such as cuttings or planting stock, are quarantined and inspected for disease symptoms or the presence of insect pests.
DNA-based testing tools, such as our PathoSEEK detection assays, can be used to screen incoming plants for pathogens before they show visual symptoms or to verify a suspected infection.