There are hundreds of different known plant viruses and viroids, with an increasing number discovered in cannabis as more research is done on this plant. Many viruses and viroids produce a similar set of symptoms in the plants they infect, and these symptoms are often captured in the name of the pathogen – mosaic, ringspot, streak, bushy, curly, crinkly, stunt, wilt, yellow vein, chlorotic, necrotic, etc. Virus names also typically include the name of the plant species in which they were first detected, however, many can infect multiple, sometimes hundreds of different species. Complicating matters, the symptoms first described for one plant species may be more (or less) severe or can appear slightly different when the same virus infects a different plant species, which can blur the lines when making diagnoses. Finally, many symptoms described for viruses and viroids are due to the plant host defense system trying to control the spread of the disease, and many of these responses can appear similar to nutrient deficiencies or abiotic stress response.

For all the similarities between viruses and viroids, there are also important differences.  Some are spread by soil, water or air, while others are insect vectored. Some are influenced by temperature or humidity level. Some can spread via pollen or in seeds, while others cannot. Determining which pathogen may be infecting your crop can help you design an appropriate response to it.  While it is important to have safeguards built into your facility, such as proper drainage, water treatment and pest control measures, pathogen testing is a sometimes-overlooked tool that can help identify and address problems early. Testing can be routinely done (on healthy tissue) or be performed for diagnostic purposes (on symptomatic tissue) and can determine whether a particular pathogen is infecting your crop, or whether it may simply have a nutrient deficiency or other stress. If a particular pathogen is identified, you will know whether to respond with deployment of beneficial insects, or if there are particular sanitary issues that need to be addressed. Culling plants may also be necessary, but knowing what is causing the symptoms will prevent the unnecessary removal of stressed or undernourished plants.

While there has been more and more research done on HLVd in recent years, there is very little information available for other viruses and viroids that infect cannabis. What follows is a brief description of what we know about the other viruses and viroids that Segra currently tests. All of these have been detected in cannabis, but not all have been thoroughly characterized to determine how they affect cannabis compared to other species in which they have been described. Based on the most current research, we have described the typical symptoms for each virus and viroid, the range of plant hosts, the known mode(s) of transmission, recommendations for prevention and treatment, and (if available) how each of these occur in cannabis.