Resources for gardeners

Know myrtle rust – and don’t touch it!

Myrtle rust forms pustules of tiny yellow spores. These spores can stick to clothes, shoes and fingers and spread to other plants – so please don’t touch it! In plants where the disease has progressed, pustules become white, then grey and infected plant material dies and turns brown/grey.

For more information on myrtle rust, please visit myrtlerust.org.nz or these Beyond Myrtle Rust programme web pages. If you suspect a plant is infected with myrtle rust, please take a photo and upload it to iNaturalistNZ.

Know your myrtles

Native myrtles include pōhutukawa, mānuka, kānuka, ramarama and rātā. Non-native myrtles include feijoa, eucalypts, bottlebrush, guavas, willow myrtle, lilly pilly and monkey apple. If you are unsure whether your plant is from the myrtle family, you can use the NZ Myrtaceae key to help identify it or upload a picture onto iNaturalistNZ for confirmation. You can also ask for more information on myrtles and myrtle rust at your local nursery or botanical garden. Garden plants that are particularly susceptible to myrtle rust are Syzygium species (monkey apple and lilly pillys) and Lophomyrtus. Here is a list of myrtle species that have been found with myrtle rust in New Zealand.

Prune myrtles in winter

Myrtle rust spores only infect new growth, including leaves, stems and flower buds. Since pruning stimulates new growth, it is best to time pruning for when the disease is least infectious – in the winter (June, July and August), not in summer.

Water myrtles on the ground in the morning

Myrtle rust thrives in humidity. To protect your myrtles, please water only in the mornings. Also, since myrtle rust attacks leaves, stems and buds, don’t water leaves. Instead, water at the base of the plant. This also helps conserve water.

Remove and or report infected plants

Since spores spread easily, it is better to remove infected plants or plant material on days that are not windy. After removing vegetation, wash your equipment and clothes. Avoid burning the plant material as updrafts can carry spores high into the air, encouraging their spread.

If you do not feel comfortable removing a plant or if it is too large to remove easily, please report the infection on iNaturalistNZ. This will help researchers track the spread of infection, and which plants are infected.

Don’t plant highly susceptible myrtles

So far in New Zealand, highly susceptible myrtles are Lophomyrtus species (ramarama and rōhutu) and cultivars such as Lophomyrtus x ralphii ‘Red dragon’, lilly pilly or monkey apple (non native Syzygium species) and willow myrtle (Agonis flexuosa) in the North Island. These susceptible plants act as vectors for myrtle rust, allowing the disease to build up in the environment. Talk to your local nursery about native alternatives for your garden. Auckland Council also provides an alternative plant list at Planting to Prevent Myrtle Rust. Consider removing and replacing susceptible myrtles currently present in your garden. They will be easier to remove when they are still healthy.