Managing Rust in Garlic

Identification

Symptoms: Orange to reddish-brown pustules on leaves, often in clusters. Severe infections cause yellowing, wilting, or premature leaf dieback.
Conditions: Thrives in warm (15–25°C), humid conditions with prolonged leaf wetness, common in spring and summer.

Choose Resistant Varieties: Some garlic varieties, particularly hardneck types, show partial resistance. Consult local suppliers for recommendations.
Crop Rotation: Rotate garlic with non-allium crops (e.g., brassicas, legumes) for 3–4 years to reduce fungal spores in soil.
Plant Spacing: Space cloves 10–15 cm apart in rows 30 cm apart to improve air circulation and reduce humidity around foliage.
Clean Planting Material: Use disease-free cloves from reputable sources. Avoid planting cloves from infected crops.
Sanitation: Remove and destroy (burn or bin) infected plant debris after harvest to limit spore spread.
Timing: Plant in autumn (March–May) to allow garlic to establish before rust-favourable conditions in spring/summer.
Weed Control: Remove weeds, which can host rust spores and increase humidity.

Watering: Water at the base of plants, preferably in the morning, to keep foliage dry. Avoid overhead irrigation.
Fertilisation: Avoid excessive nitrogen, which promotes lush foliage susceptible to rust. Use balanced fertiliser (e.g., 10-10-10) as recommended.
Monitoring: Inspect plants weekly, especially in warm, humid weather. Early detection allows timely intervention.
Remove Scapes: For hardneck varieties, remove scapes to improve air circulation and reduce disease spread.

Fungicides: In New Zealand, fungicides like copper-based products (e.g., copper oxychloride) or sulphur-based sprays are approved for garlic. Apply at the first sign of rust, following label instructions and local regulations. Rotate fungicide types to prevent resistance.
Timing: Apply protectant fungicides before rust spreads widely, typically every 7–14 days in conducive conditions.
Note: Always check with local agricultural authorities (e.g., MPI) for approved products and restrictions.

Curing: Cure bulbs in a dry, well-ventilated area for 2–4 weeks to prevent rust spores from surviving on harvested bulbs.
Storage: Store at 10–21°C with low humidity to minimise fungal activity.
Inspect: Discard any bulbs showing signs of disease before replanting.

Weather Monitoring: Rust spreads in wet, warm conditions. Use weather forecasts to anticipate high-risk periods and apply preventive measures.
Companion Planting: Some gardeners plant garlic with non-host crops like carrots or chamomile to reduce disease pressure, though evidence is anecdotal.
Organic Options: For organic growers, neem oil or potassium bicarbonate sprays may offer limited control if applied early. Focus on cultural practices for best results.

By combining prevention, monitoring, and timely management, rust can be effectively controlled to protect garlic crops and ensure healthy yields.