# Grape rust

- URL: https://backyardgrapes.com/diseases/grape-rust/
- Scientific name: Phakopsora euvitis
- Category: Fungal
- Affects: Leaves
- Severity: moderate
- Favored by: Warm, humid regions (Asia, parts of the Americas); spreads on wind-blown spores in the growing season.
- Easily confused with: Downy mildew, Black rot

**Summary:** Bright orange pustules that dust the underside of leaves, causing early leaf drop in warm regions.

**What to look for:**
- Small bright orange to yellow powdery pustules on the underside of the leaf.
- Matching yellow flecks or angular spots on the upper surface.
- Heavily infected leaves yellow, dry, and drop early.
- Early defoliation weakens the vine and can reduce ripening and winter hardiness.

**Treatment — Cultural / prevention:**
- Rake up and remove fallen infected leaves to reduce carry-over.
- Keep the canopy open and airy so leaves dry quickly.
- Choose less susceptible varieties where rust is a known regional problem.

**Treatment — Organic / low-toxicity:**
- Sulphur or copper-based protectant sprays during warm, humid spells.

**Treatment — Conventional (chemical):**
- Protectant/systemic fungicides labelled for rust where pressure is high.

Grape rust (*Phakopsora euvitis* and related species) is mainly a problem of warm, humid
grape-growing regions such as parts of Asia and the Americas; it is uncommon in cool
climates. Its signature is the mass of bright orange, powdery pustules that coat the
undersides of leaves — brush one and your finger comes away dusted with orange spores.

The rust itself doesn't rot the fruit, but by yellowing and dropping leaves early it robs
the vine of the leaf area it needs to ripen the crop and harden off for winter, so a bad
year can leave a vine weakened going into the next season. Control combines cleaning up
fallen leaves, keeping the canopy open, and protectant sprays where the disease is a
recurring regional threat.

**Image credits:**
- Grape rust: rust-coloured pustules on a grape leaf — [Plantix](https://plantix.net/en/library/plant-diseases/100352/grape-rust/)
- Grapevine leaf rust spores on the underside of a grape leaf — [Photo: Andrew M. Daly DPIFM, PaDIL, NSW Department of Primary Industries](https://www.dpi.nsw.gov.au/biosecurity/plant/insect-pests-and-plant-diseases/grape-leaf-rust)

**Sources:**
- [Phakopsora euvitis Causes Unusual Damage to Leaves and Modifies Carbohydrate Metabolism in Grapevine](https://pmc.ncbi.nlm.nih.gov/articles/PMC5623187/) — Frontiers in Plant Science (PMC)
- [Phakopsora euvitis: Addition to the EPPO Alert List](https://gd.eppo.int/reporting/article-2194) — EPPO
- [Grapevine leaf rust](https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/plants/priority-pest-disease/grapevine-leaf-rust) — Queensland Government (Business Queensland / Biosecurity Queensland)