Fusarium and Pythium species cause root and crown rots which result in wilting and, in some instances, death of the plants.
By implementing strict sanitary procedures and establishing a disease management program that meets the regulatory guidelines established for this crop, producers can reduce losses.
Root infection, caused by species of Fusarium and Pythium, initially appears as a browning of roots, followed by loss of root hairs, giving rise to a poorly developed root system.
Pathogen sources may be from contaminated growing media or containers, recirculated water, irrigation lines, or from workers handling plants.
Most producers can submit samples to commercial diagnostic laboratories to confirm the presence and severity of the pathogenic infection.
If rooted cuttings are outsourced from a supplier, they should be quarantined for at least one week to assess for symptom development or tested for pathogen presence before being used.
Microbial products, based on formulations of Trichoderma, Gliocladium and Bacillus species, provide protection but will not control diseases which have already become established.
The powdery mildew fungus develops inside epidermal cells of affected tissues and reproduces on the surface of the diseased tissues, producing large numbers of spores that can be transported by air, workers or on cuttings taken from infected stock plants.
Research is underway to characterize these resistance strains and to determine how they can be used in a breeding program.
Exposure of plants to artificial UV-C light from hand-held lamps or mechanized booms for brief daily periods of time has been shown to limit powdery mildew development.
At the time cannabis buds reach their fully developed stage and approach harvest , bud rot pathogens such as Botrytis and Fusarium develop rapidly, causing browning and rotting symptoms .
Cannabis strains that produce large and compact inflorescences create a microclimate that favours growth of the pathogen internally, and these are more susceptible to bud rot infection.
The ambient environmental conditions which promote pathogen development are relative humidity levels of over 75% and temperatures in the range of 15 to 25°C, making this a seasonal disease occurring during late summer and fall months.
To reduce the level of spores and spread, the removal of diseased buds is highly recommended.
Similar to the early applications of beneficial microbes made to rooted cuttings for the prevention of Fusarium and Pythium, there is ongoing research to explore whether competing microbes can reduce bud rot when applied to the buds prior to Botrytis infection.
There are a number of factors that can promote mold development on buds after harvest.
The most prevalent species of fungi identified to cause post-harvest mold problems include Penicillium, Aspergillus and Fusarium.
HLVd is reported to cause stunting, increased lateral growth of branches, brittle stems, changes in the appearance of leaves, and a reduction in cannabinoid content of inflorescences.
Diseased plants should be destroyed and sanitation methods implemented to reduce spread of these mechanically transmitted pathogens through cuttings and handling of plants.
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