# One plant much smaller than identical siblings: likely causes and fixes

> One plant much smaller than identical siblings on cannabis is most often Hop latent viroid (dudding), Weak or slow individual phenotype or Root aphids. How to tell them apart, the fix for each and what recovery looks like.

Also called: runt, one plant behind, one clone not growing, dud plant.

Run the checker with this sign: https://genetixbay.com/knowledge/diagnose/?at=whole&s=one-plant-stunted

## Likely causes, most likely first

### Hop latent viroid (dudding) (Possible)

- Kind: Disease; urgency: Act within a day or two
- Fix: No cure in a plant. Test mothers (roots and leaves) by RT-PCR or RT-qPCR, discard positives, disinfect tools with 10% bleach or heat (alcohol and peroxide don't inactivate it), and use meristem tissue culture to rescue valuable genetics. Don't take cuttings from stunted plants.
- Recovery: Negative tests on new mothers; no more duds in the next cycle.
- Confirm: Lab test for hop latent viroid (RT-PCR or RT-qPCR): Send root and leaf samples (roots detect HLVd earlier in young plants) to a lab offering HLVd RT-PCR or RT-qPCR. Test mother plants and any stunted plant among healthy siblings. A positive plant cannot be cured; tissue culture of meristem tips can rescue genetics.
- Confirm: Compare with siblings or the same cut: Put the affected plant beside siblings or clones of the same cut in the same conditions. A trait shared by all of a cultivar (purple stems, foxtailing, pale colour) is genetic; a problem on one plant points to its roots, a virus or its genetics; a problem on every cultivar points to the environment or feed.
- Article: [Hop latent viroid (HLVd, 'dudding') and other cannabis viruses](https://genetixbay.com/knowledge/diseases/hop-latent-viroid-and-viruses.md)

### Weak or slow individual phenotype (Possible)

- Kind: Genetics; urgency: Low urgency
- Fix: Seed-grown siblings vary; a consistently slow plant with healthy roots and a negative HLVd test is a phenotype, not a fault. Don't select it as a keeper or mother.
- Recovery: Healthy roots, negative HLVd test, otherwise normal colour.
- Confirm: Compare with siblings or the same cut: Put the affected plant beside siblings or clones of the same cut in the same conditions. A trait shared by all of a cultivar (purple stems, foxtailing, pale colour) is genetic; a problem on one plant points to its roots, a virus or its genetics; a problem on every cultivar points to the environment or feed.
- Confirm: Lab test for hop latent viroid (RT-PCR or RT-qPCR): Send root and leaf samples (roots detect HLVd earlier in young plants) to a lab offering HLVd RT-PCR or RT-qPCR. Test mother plants and any stunted plant among healthy siblings. A positive plant cannot be cured; tissue culture of meristem tips can rescue genetics.
- Confirm: Look at the roots: Hydro: lift the net pot and look at the root mass in good white light. Containers: tip the plant out with a hand over the medium and look at the edges and bottom of the root ball. Healthy roots are white to cream with fine fuzzy tips. Brown roots whose outer layer slides off between the fingers leave a bare thread: rot. Firm, evenly tan roots with white tips in coloured solution are staining.
- Article: [Slow or stunted cannabis growth: a differential](https://genetixbay.com/knowledge/diagnosis/slow-growth.md)

### Root aphids (Less likely)

- Kind: Pest; urgency: Act within a day or two
- Fix: Confirm on the roots. Apply soil-dwelling biologicals (Beauveria bassiana drenches, Stratiolaelaps scimitus, Steinernema or Heterorhabditis nematodes), sanitise, and leave a plant-free gap between cycles; dispose of infested media.
- Recovery: No live aphids on root checks after 2-3 weeks; growth resumes.
- Confirm: Root-ball and drainage-hole insect check: Tip the plant out and inspect the outer roots, pot bottom and drainage holes with a 10x loupe. Root aphids are small, pear-shaped and wingless, often with white waxy flecks; check several plants, and the drain trays, since colonies hide at the pot edge.
- Confirm: Sticky cards for 1-2 weeks: Hang yellow cards at canopy height and lay one flat on the medium surface; add blue cards for thrips. Count catches every 3-4 days. Rising counts of small dark flies at the medium mean fungus gnats; slender insects mean thrips; white wedge-shaped fliers mean whiteflies; winged aphids mean a colony nearby.
- Article: [Root aphids (rice root aphid) on indoor cannabis: ID, life cycle in numbers and IPM](https://genetixbay.com/knowledge/pests/root-aphids.md)

### Plant virus (e.g. beet curly top, lettuce chlorosis virus) (Less likely)

- Kind: Disease; urgency: Deal with it this week
- Fix: No cure: remove the plant. Control insect vectors (leafhoppers outdoors for curly top; whiteflies for some others) and test clone sources.
- Recovery: No new symptomatic plants over the next 2-4 weeks.
- Confirm: Send a sample to a plant diagnostic lab: For rots, wilts, leaf spots and viruses you can't separate by eye, send a fresh sample (whole plant with roots or a wilting branch with healthy and diseased tissue) in a sealed bag to a university or commercial plant diagnostic clinic. Results in days to 2 weeks.
- Confirm: Magnifier check of leaf undersides and new growth: Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
- Article: [Hop latent viroid (HLVd, 'dudding') and other cannabis viruses](https://genetixbay.com/knowledge/diseases/hop-latent-viroid-and-viruses.md)

## Note

Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.