5 Effective Ways to help Eliminate Pasture Rust
5 Effective Ways to help Prevent and Control Rust in Ryegrass Pastures (NZ Guide)
Rust in ryegrass — also known as Crown Rust (Puccinia coronata) or Stem Rust (Puccinia graminis) — is one of the most common fungal diseases affecting New Zealand pastures. It thrives under warm, humid conditions and can quickly impact pasture growth, quality, and animal performance.
What is Crown Rust?
Crown rust is widespread across New Zealand and is the most common type of rust seen in ryegrass paddocks.
It primarily affects:
Hybrid ryegrass
Perennial ryegrass
Tall fescue
You’ll usually first notice orange powdery spots or streaks on the leaves. These are pustules — small, round, orange-yellow blisters that appear on both sides of the leaf. Over time, they merge to form larger infected areas, and by late season, may turn dark brown or black as the fungus matures.
The pustules produce spores that are easily spread by wind and rain, infecting surrounding plants and paddocks.
Ideal conditions:
🌡️ Temperatures around 20°C
💧 High humidity or moisture (e.g. after rain or irrigation)
🌿 Overgrown, nitrogen-deficient pastures
Stem Rust — Less Common, But Still an Issue
Stem rust tends to occur more in the South Island, particularly in autumn. While not as widespread as crown rust, it can still reduce yield and persistence in susceptible ryegrass stands.
Why Rust Matters
Rusty pastures don’t just look unsightly — they cost you production.
Key impacts include:
🌱 Reduced dry matter yield and slower regrowth
🐄 Lower palatability and feed quality — animals avoid infected leaf material
💸 Reduced pasture persistence over time
🧀 Quality issues in balage, silage, and hay if infected material is harvested
While rust itself doesn’t directly cause animal health problems, affected pastures can lead to lower dry matter intake and poorer utilisation.
It can also create conditions that increase facial eczema risk (Pithomyces chartarum spores) — especially where dead or dying pasture builds up at the base of the sward.
How to Control Rust in Pastures
If rust is already showing up in your paddocks, there are several practical ways to manage it:
1. Hard Graze or Cut for Balage
Remove infected leaf material quickly. A hard graze or cutting for balage helps reduce the spore load and open the canopy for air flow.
2. Apply Nitrogen for Fresh Regrowth
Follow up with a nitrogen fertiliser or foliar feed to stimulate new, healthy growth. New leaves usually show little to no rust infection.
3. Maintain Good Grazing Management
Avoid letting ryegrass get too long. Rust thrives in dense, humid canopies where leaves stay damp. Graze at the 2.5–3 leaf stage to maintain leaf health and photosynthetic efficiency.
4. Select Rust-Resistant Cultivars
When re-sowing or renewing pastures, choose newer ryegrass varieties bred with improved rust resistance.
Older cultivars such as Nui have lower ratings and are far more susceptible.
5. Support Plant Health with Balanced Nutrition
Pastures that are low in nitrogen, potassium, or trace elements (like manganese, zinc, and copper) are more prone to disease. Foliar feeding with balanced nutrients or biologicals can improve overall plant immunity and resilience.
Are Chemical Sprays Worth It?
While fungicides (such as Prothioconazole) can help manage rust in seed crops, they’re rarely economical for standard grazing paddocks. A biological or nutritional approach is generally more practical and sustainable for most NZ farmers.
In Summary
✅ Hard graze affected pastures
✅ Cut for balage to remove infected leaves
✅ Apply N fertiliser or foliar feed for healthy regrowth
✅ Graze pastures at the correct stage — don’t let them get too long
✅ Choose rust-resistant seed varieties for longer-term resilience
🌿 Need Help Choosing the Right Seed or Foliar Program?
At Vernado, we help farmers build more resilient pastures using tailored ryegrass mixes and liquid foliar fertilisers that strengthen plant health from the ground up.
👉 Explore Our Seed Options Here
👉 Talk to Us About Foliar Fertiliser Solutions