Fungal

Mint Rust

A rust fungus causing distorted and swollen shoot tips in spring and bright orange spore pustules on leaves and stems through summer and autumn.

Symptoms to Look For

Pale, swollen, distorted shoot tips and stems in spring with no obvious pustules initially
Bright orange pustules on undersides and upper surfaces of leaves from early summer
Premature leaf yellowing and drop in heavily infected plants

Mint

Remove infected shoots

Cut back all infected stems to ground level and destroy them - the fungus overwinters systemically inside the rhizomes.

Heat treatment of runners

Submerge dormant mint runners in water heated to 44 C for 10 minutes before planting to kill systemic fungal infections in the rhizome.

Start new mint plantings from heat-treated runners in fresh uncontaminated soil
Avoid overhead watering which keeps foliage wet and encourages spore germination
Allow good air movement through the planting by dividing and thinning every 2 - 3 years

Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.