# Hop latent viroid (HLVd, 'dudding') and other cannabis viruses

> Hop latent viroid is a tiny infectious RNA that spreads through sap on tools, hands, clones, recirculating water and seed, and causes 'dudding': stunting, brittle stems and small, low-resin flowers. There is no cure in a plant. Test mothers (roots and leaves) by RT-PCR/RT-qPCR, discard positives, disinfect tools with bleach or heat (not alcohol), and use meristem tissue culture to rescue valuable genetics.

- Canonical: https://genetixbay.com/knowledge/diseases/hop-latent-viroid-and-viruses.html
- Category: Diseases · Level: Intermediate
- Evidence: Supported · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Any stage · Systems: Any system
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**Is cannabis [clone decline](https://genetixbay.com/knowledge/glossary/genetic-drift.md) real or is it HLVd?** Cannabis clone decline is, in the GenetixBay position, almost always a pathogen such as hop latent viroid, not genetic drift. Apart from pathogens, a cut does not decline; the founder keeps cuts more than 40 years old with no loss. Cuts taken from shaded lower branches can behave differently ([position effect](https://genetixbay.com/knowledge/glossary/topophysis.md)), so take cuts from consistent locations and test weak mothers.

**What is hop latent viroid in cannabis?** Hop latent viroid (HLVd) is a tiny, naked loop of infectious RNA, roughly 256 nucleotides long with no protein coat, that the cannabis plant's own enzymes copy. It is mechanically transmitted in sap and needs no insect. Research shows it is common in clone-based grows, though how common is contested, and it causes the flower problem growers call dudding.

**What are the symptoms of HLVd or dudding in cannabis?** HLVd symptoms in cannabis cannot be diagnosed by eye, and many infected plants show none, especially in veg. Some show stunting, shorter internodes, smaller narrower leaves, mild chlorosis and brittle stems that snap rather than bend. In flower, dudding means smaller, looser buds with reduced trichome density and lower cannabinoid and terpene content, and uneven performance within one clone.

**How does HLVd spread between cannabis plants?** HLVd spreads between cannabis plants through sap: on blades and scissors, hands, clones from infected mothers, roots sharing recirculating water, and seed. One researcher reported 100% infection in rooted clones from infected mothers. Defoliating a whole room with one pair of scissors is the fastest way to spread it, so disinfect blades between plants, not just between rooms.

**Does alcohol kill hop latent viroid on tools?** Alcohol does not kill hop latent viroid on tools: Oregon State tests found 70% ethanol, [hydrogen peroxide](https://genetixbay.com/knowledge/glossary/hydrogen-peroxide.md), peroxymonosulfate disinfectants and even autoclaving were not effective. What did inactivate HLVd was 10 to 20% household bleach, [hypochlorous acid](https://genetixbay.com/knowledge/glossary/free-chlorine.md) at 1000 ppm or more, or heating blades to 160 °C (320 °F) for 10 minutes. Dip or swap blades for every mother.

**How do I test my cannabis mother plants for HLVd?** Test cannabis mother plants for HLVd by RT-PCR or RT-qPCR through an [accredited lab](https://genetixbay.com/knowledge/glossary/iso-17025.md), sending roots plus leaves from several positions (top, side and bottom). The viroid can be unevenly distributed, so a single leaf can miss it, and research shows roots are a reliable tissue. Test new clones after rooting and before they enter mother or veg rooms.

**Can you cure HLVd in cannabis?** HLVd cannot be cured in a cannabis plant; no spray or product clears viroids. Discard or quarantine positive mothers and all their clones. Valuable genetics can be rescued through [meristem tip culture](https://genetixbay.com/knowledge/glossary/meristem-culture.md), which research shows yields a high rate of viroid-free plantlets at genotype-dependent rates. Retest each plantlet twice and keep clean mothers in a separate room.

**Can HLVd spread through cannabis seeds?** HLVd can spread through cannabis seeds from infected mothers or pollen, according to extension sources, though published transmission rates are scarce; one trade report suggested up to 30 to 40% of seed from infected mothers, which is unpublished. Buy seed from sources that test parents, and treat lines from untested parents as potential carriers.

**What viruses infect cannabis?** Viruses reported in cannabis include beet curly top virus, spread by the [beet leafhopper](https://genetixbay.com/knowledge/glossary/leafhopper.md) in outdoor western US hemp, and lettuce chlorosis virus, spread by whiteflies on Israeli farms and mimicking [nutrient deficiency](https://genetixbay.com/knowledge/glossary/nutrient-deficiency.md). Cucurbit chlorotic yellows virus and tobacco streak virus have also been detected. Insecticides do not stop transmission well, so control vectors and remove infected plants.

**Short answer.** Hop latent viroid (HLVd) is a tiny, naked loop of infectious RNA with no protein coat. It moves in sap: on blades, hands, clones, roots sharing recirculating water, and in seed [1][2][3]. Infected plants can look normal in veg, then "dud" in flower: stunted, brittle, with small, airy, low-resin buds [1][2]. There is no cure in a plant. Test your mothers by RT-PCR or RT-qPCR (sample roots as well as leaves), discard positives, disinfect tools with bleach or heat rather than alcohol, and rescue precious genetics through meristem [tissue culture](https://genetixbay.com/knowledge/glossary/tissue-culture.md) [3][4].

## What's happening

Viroids are the smallest known plant pathogens: HLVd is roughly 256 nucleotides of circular RNA that is copied by the plant's own enzymes and moves through the plant's vascular and cell-to-cell connections [1]. It doesn't need an insect; it is mechanically transmitted. Once in a mother, every clone taken from her carries it: Punja has reported 100 % HLVd in rooted clones from infected mothers [5].

In hydroponics it is especially troublesome because it spreads through shared water and matted roots [5]. In mother plants, the viroid can be unevenly distributed, so a single leaf sample can miss it; roots are a reliable tissue to include [4][5].

Losses are real but poorly quantified. Industry estimates of prevalence (25–50 % of North American facilities' plants) and of annual losses vary enormously and come mostly from trade sources [1][5]. The PNW Handbook notes data on the extent and incidence of HLVd are lacking [2]. *Supported* that it is common; *Contested* how common.

## How to recognise it

HLVd cannot be diagnosed by eye. Symptoms are suggestive at best, and many infected plants show none, especially in veg [1][2].
- **Veg:** sometimes stunting, shorter internodes, smaller and narrower leaves, mild chlorosis, brittle stems (snap rather than bend) [2]. Mothers that "got weak" over successive generations: this is what growers call "clone decline". GenetixBay's position is that, apart from pathogens like HLVd, a cut doesn't drift or decline; the founder keeps cuts more than 40 years old with no loss (see [clone-only preservation](https://genetixbay.com/knowledge/breeding/clone-only-preservation.md)). Two things get mistaken for decline: a rare somatic mutation (which doesn't mean a loss) and a position effect (topophysis), where cuts from shaded lower branches behave differently from cuts off vigorous leaders. Take cuts from consistent locations, so that a weak clone points to a pathogen rather than to where the cut came from.
- **Flower ("dudding"):** smaller, looser flowers, reduced trichome density and lower cannabinoid and terpene content, uneven canopy where some plants of the same clone underperform [1].
- **Rooting:** clones from infected mothers root more slowly.
- **Differential:** the same picture comes from root-zone problems, light deficits, nutrient issues and [root aphids](https://genetixbay.com/knowledge/glossary/root-aphid.md). Rule those out first ([slow growth](https://genetixbay.com/knowledge/diagnosis/slow-growth.md), [root rot](https://genetixbay.com/knowledge/diseases/root-rot-pythium.md)), then test.

## Other viruses reported in cannabis

| Agent | Spread by | Typical symptoms | Where reported |
|---|---|---|---|
| Beet curly top virus (BCTV) | Beet leafhopper | Stunting, leaf curling/twisting, pale green to yellow foliage | Outdoor hemp, western US; 81 % of Colorado leaf samples in 2019 [6][7] |
| Lettuce chlorosis virus (LCV) | Whitefly (*Bemisia tabaci*) | Interveinal chlorosis, brittle older leaves, necrosis; mimics nutrient deficiency | Licensed cannabis farms, Israel [8] |
| Cucurbit chlorotic yellows virus (CCYV) | Whitefly | Yellowing, leaf-edge necrosis in mixed infection with LCV | Israel |
| Tobacco streak virus | Thrips/pollen (in other crops) | Variable | Detected in Colorado hemp viromes [7] |
Insecticides do not stop virus transmission by vectors well; vector control plus removing infected plants is the strategy [6]. Manage [whiteflies](https://genetixbay.com/knowledge/pests/whiteflies.md), [aphids](https://genetixbay.com/knowledge/pests/aphids.md) and [thrips](https://genetixbay.com/knowledge/pests/thrips.md) for this reason as well as their direct damage. [Russet mites](https://genetixbay.com/knowledge/glossary/hemp-russet-mite.md) can transmit plant viruses in other crops (see [broad/russet mites](https://genetixbay.com/knowledge/pests/broad-russet-mites.md)).

## Numbers that matter

| Parameter | Target | Notes |
|---|---|---|
| Test method | RT-PCR or RT-qPCR from an accredited lab | Visual diagnosis is unreliable [1][2] |
| Tissue to test (mothers) | Roots plus leaves from several positions (top, side, bottom) | Uneven distribution; roots reliable [4][5] |
| Clone test timing | After rooting, before entering mother or veg rooms | *Grower practice* |
| Retest mothers | Every 4–8 weeks | Re-infection from tools or water |
| Tool disinfection | 10–20 % household bleach, or ≥ 1000 ppm hypochlorous acid, or heat blades to 160 °C (320 °F) for 10 min | Inactivated HLVd in Oregon State tests [3]; contact time for bleach dip |
| What doesn't work on HLVd | 70 % ethanol, hydrogen peroxide, peroxymonosulfate disinfectants, autoclaving | Not effective per Oregon State [3] |
| Seed transmission | Possible from infected mothers or pollen | [2][3]; trade report of up to 30–40 % of seed from infected mothers [5] |
| Meristem tip culture | High rate of viroid-free plantlets, genotype-dependent | [4] |

## What to check first

1. **Rule out cheaper explanations** for poor vigour or "duds": pH and EC, root zone, light (PPFD), temperature, root aphids.
2. **Is it clone-specific?** If one cultivar or one mother line consistently underperforms while others in the same room thrive, suspect HLVd.
3. **Test the mother**, not just the sick plant, using roots and multiple leaf positions.
4. **Audit the workflow:** shared blades between plants, defoliating with the same scissors across rooms, shared recirculating water, hands moving from mothers to clones.

## How to fix it

There is no treatment that cures a plant of HLVd [1][2].
1. **Discard or quarantine positive mothers** and all clones from them. Don't sell, gift or swap cuttings from untested plants.
2. **Rescue genetics with meristem tip culture** (the tiny growing tip, often with a heat or cold step) through a tissue-culture lab, then retest the plantlets twice before use [4]. Success depends on cultivar [4].
3. **Re-establish clean stock:** start new mothers from tested-negative material and keep them in a separate, clean room.
4. **Disinfect between plants**, not just between rooms: dip or swap blades for every mother; use bleach, hypochlorous acid or heat [3]. See [sanitation](https://genetixbay.com/knowledge/diseases/sanitation-and-prevention.md).
5. **Break water connections:** don't share recirculating solution between mothers and production; disinfect systems between cycles.
6. **Seeds:** buy from sources who test parents; treat seed lines from untested parents as potential carriers [2][3]. Seed surface disinfection does not remove viroid inside the seed.
7. **Outdoor viruses (BCTV):** remove symptomatic plants; reflective mulches may help deter leafhoppers; insecticides are ineffective against transmission [6].

### What not to do in flower
- **Don't take clones from a flowering "dud"** to see if it was a fluke. Test instead.
- **Don't spray anything** hoping to "boost" an infected plant out of it. No product cures viroids or viruses.
- **Don't defoliate a whole room with one pair of scissors.** That is the single fastest way to spread HLVd.

## How to confirm it worked

- Mothers and production plants test negative on two consecutive tests at least 4 weeks apart.
- [Uniform canopy](https://genetixbay.com/knowledge/glossary/even-canopy.md) and flower size across plants of the same clone.
- Clones root at a normal rate.

## Common mistakes

- Trusting looks: asymptomatic carriers are common.
- Testing a single leaf from a mother.
- Disinfecting with alcohol or peroxide and believing tools are clean for HLVd [3].
- Bringing in "just one" untested clone from a friend.
- Treating tissue culture as a guarantee; retest every plantlet.

## Evidence

- *Established:* HLVd infects cannabis, is mechanically transmitted and moves with clones [1][2][4].
- *Supported:* HLVd reduces vigour, flower size and secondary metabolites; many infections are asymptomatic [1][2].
- *Supported:* bleach, hypochlorous acid and heat inactivate HLVd on surfaces; ethanol and peroxide do not [3].
- *Supported:* meristem tip culture yields viroid-free plants at genotype-dependent rates [4].
- *Supported:* seed transmission occurs [2][3]; rates are not well published.
- *Contested:* prevalence and economic loss figures [1][2][5].
- *Established:* BCTV (leafhopper) and LCV (whitefly) infect cannabis/hemp [6][7][8].

## Sources

1. Adkar-Purushothama CR, Sano T, Perreault J-P, 2023. Hop latent viroid: a hidden threat to the cannabis industry. Viruses 15(3):681. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10053334/
2. PNW Plant Disease Management Handbook. Hemp (Cannabis sativa) - Viroid Diseases. https://pnwhandbooks.org/plantdisease/host-disease/hemp-cannabis-sativa-viroid-diseases
3. Oregon State University Extension. Hop latent viroid in hemp (EM 9570). https://extension.oregonstate.edu/catalog/em-9570-hop-latent-viroid-hemp
4. Punja ZK et al., 2025. Hop latent viroid transmission, spread and longevity in cannabis; meristem tip culture. Plants 14(5):830. https://www.mdpi.com/2223-7747/14/5/830
5. Cannabis Business Times, 2024. Hop latent viroid spread (report of Z. Punja talk). https://www.cannabisbusinesstimes.com/news/hop-latent-viroid-spread-zamir-punja
6. PNW Plant Disease Management Handbook. Hemp (Cannabis sativa) - Curly Top. https://pnwhandbooks.org/plantdisease/host-disease/hemp-cannabis-sativa-curly-top
7. Colorado State University (Mountain Scholar). Beet curly top virus - beet leafhopper dynamics in hemp in Colorado. https://mountainscholar.org/items/690318d0-f830-4090-b0a5-c1e18581d7b5/full
8. Hadad L, Luria N, Smith E, et al., 2019. Lettuce chlorosis virus disease: a new threat to cannabis production. Viruses 11(9):802. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6784094/