In the United States, a strange infection threatens cannabis plants

A latent hop viroid, the HpLVd (or HLVd) is causing concern among American growers. This phytovirus is particularly rife in California, world capital of plant cloning. The main symptom of an infected plant: none. As with covid-19, many cannabis plants can be asymptomatic, making it difficult to spot.

Then, from one day to the next, the symptoms reappear. They manifest themselves in a loss of vigor, a sickly appearance of the plant, and a 30 % slowdown in growth. Above all, a «loss of overall flowering production of 30% (reduced flower size and weight, reduced resin production, reduced intensity of odour, flavour and potency)».», learns about the Humboldt seed bank. In short: fewer flowers, fewer sales.

This viroid (smaller than a virus) originates from the hop plant. not so far removed from cannabis. He was then spotted for the first time on a cannabis plant in 2017. This discovery was made by Dark Heart Nursery. Researchers from this Californian laboratory then toured farms to test for HpLVD. The results were striking.

44 million in annual losses

«Most farms had an infection rate of around 25 to 50 %, causing an estimated loss of $44 million a year.», says the lab. If losses are so high, it's because there's simply no way of curing a diseased plant. The best a grower can do is to prevent the viroid from spreading further throughout the farm.

There's only one rule: hygiene. If you cut an infected plant with pruning shears, then prune another plant with the same tool, it will be infected in its turn. Humbolt Seeds advises growers of «clean all your pruning tools thoroughly».». You should also avoid «Touching an infected plant and then touching a healthy one, or leaving these two types of plant in frictional contact».».

Some, like 2Fast4Buds propose to treat infected plants. To do this, he recommends taking a cutting from a plant, then soaking it in a solution of fungicide and water. The cutting should then be left to root for a few days. Then soak it again in a fungicide-water solution. But this technique needs to be tested on one or two plants before being deployed on a large scale.