# Fusarium in cannabis: wilt, crown rot and bud rot

> Fusarium fungi cause three different problems in cannabis: vascular wilt (F. oxysporum), root and crown rot (mainly F. solani), and a pinkish-white bud rot. There is no cure once a plant is infected; remove it, stop root-zone stress, sanitise pots and water, and source clean clones and media.

- Canonical: https://genetixbay.com/knowledge/diseases/fusarium.html
- Category: Diseases · Level: Intermediate
- Evidence: Established · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Seedling, Veg, Flower · 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

**Why is my cannabis plant wilting on one side?** A cannabis plant wilting on one side or one branch, during the day and without recovering, is a classic sign of Fusarium vascular wilt, caused by Fusarium oxysporum colonising the xylem and blocking water flow. Lower leaves yellow and drop, and there is typically no obvious [root rot](https://genetixbay.com/knowledge/glossary/root-rot.md). Cut the stem near the base: brown or reddish-brown streaks in the wood confirm it.

**What does Fusarium look like in cannabis?** Fusarium in cannabis looks different depending on the disease. Vascular wilt shows yellowing, wilting leaves and brown streaks inside the stem. Crown rot shows a dark, soft or sunken lesion at the stem base, sometimes with white-pink growth, plus brown roots and stunting. Fusarium [bud rot](https://genetixbay.com/knowledge/glossary/botrytis.md) appears as whitish to pinkish mould on or inside buds in warm, humid late flower.

**Why is the inside of my cannabis stem brown?** Brown or reddish-brown streaking in the wood of a cannabis stem, seen when cut near the base, points to Fusarium vascular wilt, according to extension sources. Verticillium wilt causes similar streaking and can only be told apart by a lab culture or molecular test. Clean, pale wood with rotten roots instead suggests root rot from Pythium or Fusarium.

**Is Fusarium wilt in cannabis curable?** Fusarium wilt is not curable in an infected cannabis plant, and extension sources note few or no fungicides are registered for it on hemp. Remove the wilting plant with its roots and media, bagged, and do not compost it on site. Then fix root-zone stress, disinfect reused pots with a 10 to 15% household bleach solution and use pasteurised media and clean clones.

**How can I tell Fusarium from Pythium in cannabis?** Fusarium and Pythium in cannabis differ mainly in the roots and stem. Pythium makes roots slimy, with an outer layer that sloughs off, and causes no vascular streaking. Fusarium wilt causes brown streaks inside the stem, often with no obvious root rot, while Fusarium crown rot softens and discolours the stem base. Research shows both can infect the same plant.

**What causes pink mould on cannabis buds?** Whitish to pinkish mould on or inside cannabis buds, especially in warm, humid late flower, is typical of Fusarium bud rot. Research recovered Fusarium solani and Fusarium oxysporum from cannabis buds, where they add to yeast and mould counts and may produce [mycotoxins](https://genetixbay.com/knowledge/glossary/mycotoxins.md). Treat mouldy flower as waste, and keep late-flower humidity at about 40 to 50% to prevent it.

**Short answer.** "Fusarium" covers three different problems in cannabis. **Vascular wilt** (*Fusarium oxysporum*) blocks the plant's plumbing so it wilts, often one branch or one side first, with brown streaks inside the stem [3]. **Root and crown rot** (mainly *F. solani*) rots roots and the stem base [4]. **Fusarium bud rot** shows as pinkish-white mould in flowers [2]. None is curable in an infected plant. Remove it, fix the root-zone stress that let it in, sanitise, and start from clean clones and clean media.

## What's happening

*Fusarium* species live in soil, plant debris, unpasteurised media and water. They enter through root tips and wounds ([transplant](https://genetixbay.com/knowledge/glossary/transplanting.md) damage, [fungus gnat](https://genetixbay.com/knowledge/glossary/fungus-gnat.md) feeding, salt burn) [2][5].
- **Wilt:** *F. oxysporum* (formae speciales *cannabis* and *vasinfectum* reported on hemp) colonises the xylem. Water flow stops; leaves yellow and wilt from the bottom or on one side. There is typically no obvious root rot [3].
- **Crown and root rot:** *F. solani* (primarily), *F. equiseti* and *F. graminearum* rot the roots and soften and discolour the crown just above the soil line [4]. In hydroponic cannabis, *F. oxysporum*, *F. solani* and *F. brachygibbosum* caused root browning, crown and pith discolouration, stunting and yellowing [1][2].
- **Bud rot:** *F. solani*, *F. oxysporum* and other species were recovered from cannabis buds and can contribute to yeast-and-mould counts [2].
Stress, warm and wet or alternately wet-and-droughty media, and poor [drainage](https://genetixbay.com/knowledge/glossary/runoff.md) favour wilt and crown rot [3][4][8].

## How to recognise it

- **Wilt:** lower leaves yellow and drop; a branch or one side of the plant wilts during the day and doesn't recover; whole plant can collapse in flower. **Cut the stem near the base:** brown or reddish-brown streaking in the wood (xylem) is the giveaway.
- **Crown rot:** dark, soft or sunken lesion at the stem base, sometimes with white-pink fungal growth; roots brown and rotting; plant stunted and yellow.
- **Hydro root infection:** root browning with crown and pith discolouration [1].
- **Bud rot:** whitish to pinkish mycelium on or inside buds, often in warm, humid late flower.
- **Look-alikes:** Pythium (slimy roots that slough, no vascular streaking — see [root rot](https://genetixbay.com/knowledge/diseases/root-rot-pythium.md)); Verticillium wilt (similar streaking, favoured by consistently moist soils [8]; lab test needed); drought or [overwatering](https://genetixbay.com/knowledge/glossary/overwatering.md) wilt (recovers when corrected; no streaking); stem borer damage outdoors.

## Numbers that matter

| Parameter | Target | Notes |
|---|---|---|
| Root-zone moisture | Even, with [dry-back](https://genetixbay.com/knowledge/glossary/dryback.md); no waterlogging, no extreme drought cycles | Overly wet or droughty soils favour Fusarium wilt [8] |
| Solution temperature (hydro) | 18–21 °C (65–70 °F) | Reduces root stress and Pythium co-infection (*Supported*) |
| Disinfection of reused pots/trays | 10–15 % household bleach solution | Utah State recommendation [3]; clean off soil first |
| Field rotation after wilt | 2–3 years (Utah) to ≥ 4 years (Oregon) out of hemp | Sources differ [3][8] |
| Late-flower RH (bud rot) | 40–50 % | Same targets as botrytis (*Supported*) |
| Pasteurised media | Use new or pasteurised coco/peat | Unpasteurised coco can carry fungal contaminants [2] |

## What to check first

1. **Cut a stem section** at the base of a wilting plant (or a lower branch you can spare). Streaks in the wood = vascular wilt. Clean wood + rotten roots = root rot (Pythium or Fusarium).
2. **Check the [root zone](https://genetixbay.com/knowledge/glossary/root-zone.md):** waterlogging, saucers, compacted media, drought cycles, salt burn from high EC.
3. **Check for fungus gnat larvae** and [root aphids](https://genetixbay.com/knowledge/glossary/root-aphid.md) in the media; both wound roots.
4. **Check the source:** new clones, reused soil, unpasteurised media, untreated surface water.
5. **Send a sample to a plant diagnostic lab** if you need certainty. Fusarium and Verticillium can only be told apart reliably by culture or molecular test.

## How to fix it

### Infected plants
- **Remove wilting plants with their roots and media**, bagged, out of the grow. Utah State recommends removing infected plants with roots [3]. Don't compost them on site.
- In [recirculating hydro](https://genetixbay.com/knowledge/glossary/recirculating-system.md), isolate the plant's site from the loop immediately.

### Cultural and environmental
- Water by weight or sensor; allow dry-back; never leave pots sitting in drainage.
- Avoid root damage: gentle transplants, no cultivating near stems, manage gnats.
- Use new pots and trays, or disinfect reused ones [3]. Clean equipment between rooms or fields [3].
- Use pasteurised media and clean planting stock from a reliable source [7].
- Outdoors: avoid heavy, poorly draining soils [8]; rotate out of hemp as above.
- Late flower: open canopy and keep RH below 50 % against bud rot.

### Biological and least-toxic options
Utah State and NC State note that no or very few fungicides are registered for these diseases on hemp [3][5]. Registration varies; check local regulations and labels.
- **Root-zone biologicals** applied preventively: *Trichoderma* spp., *Bacillus* spp., *Streptomyces* spp., *Gliocladium/Clonostachys*. *Supported in other crops* for Fusarium suppression; limited cannabis-specific evidence.
- **Compost-amended or [living soils](https://genetixbay.com/knowledge/glossary/living-soil.md)** may suppress some root pathogens (*Supported in other crops*), but poorly made compost can also introduce them.
- **Resistant genetics:** no tested resistant cannabis cultivars are documented in these sources.

### What not to do in flower
- **Don't try to nurse a wilting, streaked plant to harvest** in a shared space; it sheds spores into media and water.
- **Don't drench with unregistered fungicides.** Residues, legality, and they don't cure vascular infection.
- **Don't harvest or process buds with pink or white internal mould.** Fusarium species can produce mycotoxins; treat mouldy flower as waste [2].
- **Don't reuse that plant's media** in flower or next cycle.

## How to confirm it worked

- No new wilting in neighbouring plants over 2–3 weeks.
- Stem cuts from suspect plants show clean, pale wood.
- Next crop in disinfected pots and fresh media establishes without lower-leaf yellowing or crown lesions.
- If you sent a sample, a lab result tells you which pathogen to plan for.

## Common mistakes

- Watering a Fusarium-wilted plant harder because it's wilting.
- Reusing soil and pots from an infected crop without treatment.
- Assuming every wilt is Fusarium (or every root rot is Pythium). Both can co-occur [1].
- Buying cheap, unpasteurised media.
- Ignoring fungus gnats.

## Evidence

- *Established:* *F. oxysporum*, *F. solani* and *F. brachygibbosum* infect cannabis roots and crowns; *F. solani* and *F. oxysporum* occur in cannabis buds [1][2].
- *Established:* wilt and crown rot are distinct diseases with different species and symptoms [3][4].
- *Supported:* poor drainage, overwatering and drought stress increase risk [3][4][8].
- *Contested:* rotation length outdoors (2–3 years vs ≥ 4 years) [3][8].
- *Supported in other crops*, limited cannabis data: biological suppression.

## Sources

1. Punja ZK, Rodriguez G, 2018. Fusarium and Pythium species infecting roots of hydroponically grown marijuana (Cannabis sativa L.) plants. Canadian Journal of Plant Pathology 40(4):498–513. https://doi.org/10.1080/07060661.2018.1535466
2. Punja ZK et al., 2019. Pathogens and molds affecting production and quality of Cannabis sativa L. Frontiers in Plant Science 10:1120. https://www.frontiersin.org/articles/10.3389/fpls.2019.01120/full
3. Utah State University Extension. Hemp Fusarium wilt (IPM Notes). https://extension.usu.edu/planthealth/ipm/notes_ag/hemp-fusarium-wilt
4. Utah State University Extension. Hemp Fusarium crown rot (IPM Notes). https://extension.usu.edu/planthealth/ipm/notes_ag/hemp-fusarium-crown-rot
5. NC State Extension Plant Pathology. Root diseases prevalent in industrial hemp. https://plantpathology.ces.ncsu.edu/news/root-diseases-prevalent-in-industrial-hemp/
6. PNW Plant Disease Management Handbook. Hemp (Cannabis sativa) - Root and Crown Rot. https://pnwhandbooks.org/node/12931
7. BC Ministry of Agriculture. Diseases of cannabis in British Columbia (factsheet). https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/agriculture-and-seafood/animal-and-crops/plant-health/disease-factsheets/specialty-crops/diseases_of_cannabis_in_british_columbia.pdf
8. Oregon State University Extension, hemp disease guidance. https://extension.oregonstate.edu/node/190521