Myrtle rust taking off again
Recent increases in the number of myrtle rust reports on iNaturalist suggest the disease is, unfortunately, being helped by the warm wet conditions much of the country is now experiencing. November saw 188 observations, following just 27 in October and 23 in September. I am informed that exotic Myrtaceae hedges across Auckland are "lit up like Christmas trees" - and not in a good way! If you have one of these hedges, it would do our native trees a real favour if you could remove it - fewer spores blowing around = less chance of infection on native forest plants. And spores can travel a long way! It is also now best to water only at the base of myrtle plants in your garden (to keep the above-ground plant parts dry), and hold off until autumn before pruning and fertilising. This will reduce production of the new growth that is most vulnerable to myrtle rust. For more tips, and notes on reducing biosecurity risks when removing plants, see here for myrtle rust FAQs: https://www.landcareresearch.co.nz/discover-our-research/biosecurity/ecosystem-resilience/beyond-myrtle-rust/faq/
Meanwhile, myrtle rust continues to spread through our native forests. A recent record of myrtle rust on Lophomyrtus in Hokitika is notable - the first from the west coast of the South Island this season. If you are out and about, especially in native forest areas, do keep an eye out for myrtle rust and keep putting up your pictures. Scientists and land managers appreciate this.
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Just need a clarification please - I’d like to remove my Lilly pillies (infected), but it says in your post to hold off pruning. In the past I sprayed mine (they’re small) with hairspray, then cut off at the base and bagged. Can I still do this over summer? Or wait until autumn? Thanks.
Hi there. You raise an interesting conundrum. Re pruning - this is relatively straightforward in that one is waiting to avoid encouraging vulnerable new growth during peak season. When a plant is being removed, there will be no new growth. However the removal process itself will likely cause the release of at least some spores into the air. If you leave the plant though, it will continue to release spores throughout the season. it is impossible to calculate which choice will result in the greatest release of spores. Especially as we cannot predict future weather conditions. I would suggest if the trees are still small enough to do something to reduce the release of spores, do that and remove them now, especially if you can get it done on a day that is not windy. Unfortunately, there is no 'cure' that is coming for people's infected hedges.
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