# Grapevine fanleaf virus

- URL: https://backyardgrapes.com/diseases/fanleaf-virus/
- Scientific name: Grapevine fanleaf virus (GFLV)
- Category: Viral
- Affects: Leaves, Roots
- Severity: high
- Favored by: Spread by dagger nematodes (Xiphinema) feeding on roots, and by propagating infected cuttings.
- Easily confused with: Grapevine leafroll, Grapevine red blotch, Herbicide drift, Zinc deficiency, Boron deficiency

**Summary:** A nematode-spread virus that deforms leaves into a fan shape and leaves the crop straggly.

**What to look for:**
- Distorted, asymmetric, fan-shaped leaves with an abnormally wide (open) petiole sinus.
- Bright-yellow mottling or vein-banding ("yellow mosaic") in some strains.
- Shoots with short internodes, zig-zag growth, double nodes, and flattened (fasciated) stems.
- Poor fruit set — straggly clusters with many small "shot" berries and declining yield.

**Treatment — Cultural / prevention:**
- Plant certified virus-free vines from a reputable nursery — the single most important step.
- Remove and destroy infected vines; they only get worse and act as a source.
- Manage the dagger-nematode vector before replanting (fallow, remove old roots, resistant rootstocks).

**Treatment — Organic / low-toxicity:**
- There is no cure for a virus — clean planting stock and roguing are the whole strategy.

**Treatment — Conventional (chemical):**
- Pre-plant nematode control is used in some settings to limit spread through the soil.

Grapevine fanleaf virus is one of the oldest and most damaging grape viruses. Its name
comes from the leaves, which grow distorted and splayed like an open fan, often with an
unusually wide gap where the petiole meets the blade. Some strains add bright-yellow
mosaic patterns; all of them tend to wreck fruit set, leaving loose clusters of tiny,
seedless "shot" berries and a shrinking harvest year after year.

The virus moves two ways: through infected cuttings (so it travels the world in nursery
stock) and through dagger nematodes that pick it up feeding on infected roots and carry
it to healthy ones. There's no spray that cures a virus. The answer is clean stock at
planting and dealing with the nematodes in the soil before you replant an infected site.

**Image credits:**
- Grapevine fanleaf virus symptoms on grape leaves — [Oklahoma State University Extension](https://extension.okstate.edu/programs/digital-diagnostics/plant-diseases/grapevine-fanleaf-virus.html)
- Fan-shaped, asymmetric leaf with an open petiolar sinus caused by grapevine fanleaf virus — [Photo: William M. Brown Jr., Bugwood.org, Bugwood.org](https://www.ipmimages.org/browse/detail.cfm?imgnum=5356702) (CC BY-NC 3.0 US)
- Zigzag shoot growth with small cupped leaves, a fanleaf virus symptom — [Photo: William M. Brown Jr., Bugwood.org, Bugwood.org](https://www.ipmimages.org/browse/detail.cfm?imgnum=5357022) (CC BY-NC 3.0 US)

**Sources:**
- [Fanleaf degeneration/decline disease of grapevines](https://ecommons.cornell.edu/handle/1813/43094) — New York State IPM Program, Cornell University
- [Nematodes (Grape Pest Management Guidelines)](https://ipm.ucanr.edu/agriculture/grape/nematodes/) — UC IPM
- [Major Grapevine Diseases: Fanleaf and Leafroll](https://pubs.extension.wsu.edu/major-grapevine-diseases-fanleaf-and-leafroll) — Washington State University Extension