“The problem is the cannabis industry for the past 20 years at least was based on clones only,” Badad said.
“So everybody is shipping clones from here to there, and nobody was testing, or nobody was aware of any methodology to test for this virus.
“What we did was basically spread it all over the planet. Anybody receiving any plants from the United States, especially from California, has the viroid in their grow.”
Small and stealthy
Experts warned the viroid is stealthy. It’s also very small, asymptomatic and waiting for an opportunity to infect a plant.
The most likely form of transmission is from the everyday trim tools used for vegetative propagation and grafting or human hands.
When the viroid attacks, the plant pathogen moves quickly from the roots to the leaves to the flower in two to three weeks, Punja said.
It is most problematic in hydroponics – rather than outdoor grows – because the viroid can move through water and more easily infect roots that tend to be matted together.
Hop latent viroid doesn’t outright kill the plant.
But a grower can see an infected plant struggling to grow normally because the plant is shorter and the trichomes are underdeveloped or stunted.
The result: lower THC and CBD levels, which can drop as much as 40%.
“It’s almost like the plant just doesn’t have that energy to put into those trichomes,” Punja said.
It’s most noticeable when the plant flowers, Punja said.
He and other researchers suggest it’s that part of the growing cycle where the viroid might become more virulent, perhaps because of the stress the hydroponic plant is undergoing during the 12-hours-on, 12-hours-off lighting change that occurs during the flowering stage.
As a precaution, growers should have their plants tested, down to the roots, Punja said.
But even then, there are no assurances.
“Unfortunately, one test is not enough,” Punja said. “What we’re finding is that the first test will be negative.
“Three weeks later, again negative. Then three weeks later, positive.”
It’s unavoidable
The viroid is likely to be in the soil of grows, researchers said. It’s also in the water of a hydroponic grow. And it’s definitely in the roots.
In addition, the pathogen is in the seed, not on the seed. It also can spread to one’s hands as a grower handles plants, moves them, stacks them, hangs them.
Even one infected plant brushing up against another can transfer the viroid.
Any sort of sap-sucking insect that makes a hole in the plant, especially at the roots, can create a pathway to infection.
The insect itself does not carry the viroid from plant to plant, as far as researchers know now, Punja said.
The viroid also could be airborne. “Other viroids are,” Singh said. “So it may not be that big a stretch to say that it would be in the pollen.”
The viroid is likely to be present in most commercial licensed cannabis production facilities in the United States and Canada.
The frequency of infected plants is estimated to be in the range of 25%-50% in both countries, according to Punja.
Testing by clone cultivator Dark Heart Nursery on 100 cannabis growers in California from August 2018 to July 2021 found that one-third of plants in 90% of those grows were infected.
That finding supports projections that the viroid affects more than 30% of all cannabis plants in the United States.
