MR BIOLOGY WEBINAR: Monitoring Austropuccinia ...

Monitoring the impact of Austropuccinia psidii on native Myrtaceae in the ngahere

August 2021

Sutherland R. 2021. Monitoring the impact of Austropuccinia psidii on native Myrtaceae in the ngahere. Beyond Myrtle Rust Webinar Series. 11/08/2021

ABSTRACT

Since the arrival of myrtle rust in May 2017 to Aotearoa, the fungus responsible for the disease (Austropuccinia psidii) has spread across all regions of Te Ika-a-Māui, the North Island and parts of Te Waka-o-Māui, the South Island. The disease impacts native and non-native Myrtle species in urban areas and the ngahere (forest). Rōhutu and ramarama (Lophomyrtus spp.) are among our most susceptible species with severe infection recorded on leaves, stems, flowers, fruit and in some cases, death of seedlings and mature trees. Regeneration of these species is likely to be negatively impacted and localised extinction possible. Long term monitoring plots were established in 2018 in the Bay of Plenty region, in an area where a variety of different myrtle species naturally occur including ramarama, rōhutu, mānuka, climbing rātā and pōhutukawa. Mature trees and seedlings are monitored fortnightly for disease severity and extent within the area. Data from this monitoring show that disease impacts have increased over the past three summers, possibly due to increasing myrtle rust inoculum load in the environment.

Ecosystem impacts from myrtle rust extend beyond plant loss. In forests across New Zealand, where Myrtaceae are present, the loss of these species could have severe consequences on invertebrate and vertebrate communities, highlighting the cascading environmental impacts to forest ecosystems. Surveillance and monitoring will play a critical role in identifying ecosystems and populations at risk.