Cannabis and Virus: How they spread and how to destroy them
What are phytoviruses or viruses that attack plant organisms?
Viruses that infect plant organisms called phytoviruses are parasites that use the plant as a host or reproduction host.
They are formed by a protein cover called a capsid that surrounds the genetic material, nucleic acids (RNA or DNA), in most plant viruses the genetic material is a chain of RNA.
The first virus detected in plants was the tobacco mosaic virus, discovered by Dmitri Ivanovski and Martinus Willem Beijerinck in the late 19th century that wreaks havoc on tobacco plants and is believed to be able to infect cannabis as well.
How do they spread?
Once inside the cell the capsule is detached and the genetic material is replicated along with that of the cell creating new copies of the virus, infecting new adjacent cells, they can also "travel" with sap reaching new parts of the plant.
Viruses by themselves are incapable of transferring to other plants, for their dispersion they need "vectors", that is, any organism capable of transporting the virus from one plant to another.
Typical cannabis pests such as aphids, whiteflies, or thrips can act as vectors but also numerous insects and nematodes. Sometimes they can be found in substrates, seeds and pollen of infected plants as well as in the grower themselves or the cultivation tools that have previously had contact with infected plant material.
The most common symptoms are dwarfism, mosaic, mottling, chlorosis, necrosis, and deformation.
The mosaics are areas of the leaves where light green, yellow, dark green even gold combinations appear. Localized lesions are chlorotic spots or spots that end up necrotizing as well as yellowing in the form of stripes or striae. Also, curling of the leaves, curving up or down, dwarfism or reduction in leaf growth and internodal distances giving small or stocky plants.
Some of these symptoms could be mistaken for nutrient deficiencies, genetic mutations, or root problems. If your plants are growing vigorous, with no other symptoms, and you don't see spread to other plants, you shouldn't worry, as it's probably not a virus infection.
What are the viruses that attack cannabis?
Alfalfa mosaic virus (AMV): chlorotic streaks along leaves, light green mottling with chlorotic streaks in veins and slight wrinkling in leaves. It is transmitted mainly by aphids, also seeds or cuttings.
Cucumber mosaic virus (CMV): mottled on leaves, light green spots that diffusely cover the surface of the leaves, especially the young ones. Vectors are aphids, seeds, and pollen.
Arabis mosaic virus (ArMV): green-yellow spot or mosaics and stripes on leaves and weak growth. Transmission by seeds and nematodes.
Hemp striatum virus (HSV): pale green chlorosis in leaves, where yellow stripes develop. Necrotic spots surrounded by light green sometimes appear on the margins and tips of the leaves that also wrinkle.
Hemp mosaic virus (HMV): causes foliar curl, stunting on leaves, as well as chlorotic spots that end up necrotizing. Transmission by sap, seeds, whitefly, aphids and thrips.
There is no treatment that we can apply to cure the plant of a virus infection, therefore prevention is our most important tool.
Cleaning and hygiene of the growing area after every harvest and of the utensils each time we use them, washing our hands before handling the plants or wearing gloves, everything we can do to avoid introducing anything contagious into the crop.
Always start with seeds from banks with guarantees, when using an infected plant as a mother you have a good chance that the virus will pass to clones and / or seeds.
Vector control, in a pest-free crop you prevent insects from spreading the infection to other plants.
Once the virus infection progresses in the plant, the best we can do is discard it as soon as possible and burn it down, it is the best way to ensure that the virus will be destroyed.