Naturally West: Myrtle rust

Is Myrtle Rust in Your Backyard?

Myrtle rust as it presents on Eucalyptus. Photo courtesy of Department of Conservation. Myrtle rust has now been found in the Waitākere Ranges at Karamatura, near Mount Donald McLean. It has spread across the West, the wider Auckland area and elsewhere across the country wherever the climate is compatible with the disease.

Myrtle rust disease is a serious biosecurity threat. It is caused by a fungus that spreads in the air. People can also move fungal spores around and introduce the disease to new hosts and areas where it may not independently arrive. Plants in the myrtaceae (myrtle) family are at risk from dieback and death. Notable members of this plant family include pōhutukawa, rātā, kānuka, mānuka/tea tree, ramarama, lilly pilly, feijoa, guava, willow myrtle, gum trees/eucalyptus and bottle brush.

Myrtle rust attacks new shoots, fruits and flowers, and can destroy the food relied on by some species of native birds, lizards and insects. There is the possibility that some of these tree species could become regionally extinct, and their loss could have serious flow-on effects to ecosystem services like erosion control and nutrient cycling.

The good news is that a trans-Tasman research collaboration announced last year has successfully completed a nearly complete genome for the fungus that causes myrtle rust. The genome is invaluable to researchers working to understand the process that this fungus uses to infect its host and cause disease. This will mean that specific control strategies can be developed.

To reduce the risk of spreading the disease, avoid brushing against infected trees. Use clean equipment and check it when you leave and return home. If you see yellow spores on your clothing, turn it inside out and store it in a plastic bag before washing it. Clean skin with soap and water to remove and kill spores. Wipe down phones and other sensitive gear with alcohol-based products, such as hand-sanitisers or methylated spirits.

To see how the disease presents on a range of species, visit https://www.inaturalist.org/taxa/549208Austropuccinia-psidii/browse_photos

Information is urgently needed on the whereabouts, hosts, and intensity of this disease in New Zealand.

Reporting myrtle rust via the iNaturalist app provides valuable information to land managers and researchers. Photos of disease symptoms and of the host should be sent to https://www.inaturalist.org/projects/myrtlerust-reporter where you can click on the ‘Observations’ link to post your images.

Identify your observation as ‘myrtle rust’ in the ‘what did you see’ field. The iNaturalist community will help confirm your observations. You can also add further information about the infection in the observation form in this project. Repeated observations are welcome – every report helps track changes in the disease.

You can take pictures using a smart phone within the app or use a camera and upload the images via the website later. Helpful images include: 1. Close-up images of symptoms (usually yellow powdery spores) 2. Images of the leaves, and any flowers or fruit if present 3. View of the plant(s) as a whole (if possible), to show the surrounding habitat/environment

You can add healthy trees too. Make observations of myrtaceae when you see them as well, including images of 2 and 3 above.

For more information about myrtle rust, particularly as it relates to your own backyard visit https://www. myrtlerust.org.nz/about-myrtle-rust/ where there is information about what to do if you find myrtle rust. There are videos that outline the options of either not treating and monitoring the affected trees or removing the diseased trees. The website also provides links showing how to remove infected myrtle plants and safely dispose of the waste (It may be useful to enlist an arborist should you choose to remove the trees.)

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WORST WEEDS WATCHLIST

Have you spotted these in your backyard? Pest plants have a real ecological impact when they jump the garden fence and smother our forests and streams. Keeping them at bay means that native plants and birds can flourish.

CLIMBING ASPARAGUS MOTH PLANT WILD GINGER

Smothers the forest floor and prevents growth of native plants. Climbing plant with small, thin leaves, white flowers and green berries that ripen to orange/ red. For small amounts, dig out tubers, rhizomes and seeds & rot in a water barrel or dispose in community weed bins. Try to remove before seeding occurs. Large infestations may require herbicide.

WOOLLY NIGHTSHADE

Quickly forms dense stands that prevent native plants from growing. Small shrubs grow into large trees with furry grey/green leaves, purple flowers and green fruit turning yellow when ripe. Dig or pull out small plants or cut and paste large trees with herbicide. Remove seeds and dispose of in community weed bins. Strangles native plants and is a prolific seeder. Noxious woody vine with white sap and large green pods bearing up to 1000 seeds. Wear gloves when removing pods and dispose of in community weed bins. Pull out young plants at the root, or cut woody stumps and apply herbicide. Avoid skin contact - sap is an irritant. Quickly forms dense stands that prevents native plants from growing. Cut off seed heads and dispose at community weed bins. Green stems and leaves can be left to compost. If rhizomes can be removed without causing erosion, dig out and rot in water barrels or dispose in community weed bins. If leaving rhizomes in the ground, cut stems at base and paste immediately with herbicide.

JASMINE

Grows densely and smothers native plants on the ground and in the subcanopy. Evergreen climber with tough stems, dark green leaves, red/pink flower buds and white, five-petalled flowers. Cut vines and leave upper stems to die in trees, alternatively dig out roots. Rot down in a water barrel or dispose in community weed bins.

TRADESCANTIA

Forms dense mats preventing native plants from growing, and will regrow from stem fragments. Rake up or pull out all pieces and compost in a weed bag, or dispose of in community weed bin.

For large infestations or more detailed information, visit https://pestsearch.aucklandcouncil.govt.nz To prevent the spread of kauri dieback, refrain from removing weeds from around the root zones of kauri. Those who live in the Waitākere Ranges Local Board area can dispose of invasive weeds free of charge at the community weed bins: www.ecomatters.org.nz/weed-bins