Cannabis growers face a short list of pathogens that cause most of the losses, and nearly all of them are easier to prevent than to cure. This page summarizes the major documented cannabis pathogens, how they move, how laboratories detect them, and the environmental conditions that favor them, with sources behind every claim.
The Major Documented Pathogens
Major documented cannabis pathogens include Botrytis cinerea, Pythium and Fusarium species, and powdery mildews. Management relies on sanitation, environmental control, and resistant or healthy planting stock. Notice what is absent from that list: a cure after infection. Prevention is the strategy because options after infection are poor.
HLVd Moves On Tools, Not Airflow
Hop latent viroid spreads primarily through mechanical transmission of contaminated sap via tools during pruning and cutting propagation, and there is no curative treatment once a plant is infected. In a cloning operation this makes blade hygiene a biosecurity control, not a nicety: one contaminated scalpel can move viroid through an entire propagation batch.
The Silent Part Of An HLVd Infection
HLVd infection can be asymptomatic while reducing vigor and yield. A plant can look acceptable while underperforming, which defeats buy-by-appearance. That asymmetry between how a plant looks and what it carries is the core argument for laboratory screening over visual inspection.
How Laboratories Detect It
RT-qPCR is the standard laboratory detection method for HLVd. Polymerase chain reaction looks for the viroid's genetic material rather than symptoms, which is why a PCR result can be trusted for material that appears clean while a visual pass cannot.
When It Reached California Cannabis
HLVd was first reported in California cannabis in 2019, in plants showing cannabis stunting disease symptoms. The industry's awareness of dudding disease is recent, and screening programs are newer still. Older catalogs built before routine PCR testing may have carried infections nobody had a method to see.
Powdery Mildew's Favorite Conditions
Powdery mildew favors moderate temperatures of roughly 60 to 80 degrees Fahrenheit, shade or low light, and high relative humidity, and its spores germinate without free water on leaf surfaces. That last detail surprises growers: unlike most fungal problems, you cannot prevent powdery mildew just by keeping foliage dry. Dense canopies and stagnant air do the rest.
Root And Flower Pathogens
Pythium species attack roots and thrive in overly wet, poorly oxygenated media. Fusarium attacks vascular tissue and can persist in growing medium. Botrytis cinerea buds rot from the inside, often inside dense flowers. Each has distinct conditions it exploits, but all reward the same grower habits: clean media, working airflow, and planting stock that started healthy.
Management Basics That Hold Up
For all of these pathogens, management rests on sanitation, environmental control, and healthy planting stock. Disinfected tools, quarantined new arrivals, monitored humidity, and screened mothers are the levers that actually exist. Everything else is hoping.
Screening Before You Buy
Clone Source screens mother stock by PCR for HLVd, Fusarium, and Pythium, and testing documentation tied to the record you are ordering is available on request before fulfillment. Start with our detailed HLVd testing guide, review testing documentation standards, then browse the catalog for records with current availability.