Lophomyrtus bullata is a shrub or small tree, endemic to Aotearoa / New Zealand where it occurs on Te Ika a Maui / North Island and Te Wai Pounamu / South Island. A few scattered records are known from offshore islands of North Island, including on Aotea / Great Barrier Island and Kapiti Island. The estimated population size is more than 500,000 mature individuals in situ. However, this is a reduction from a probable excess of 1,000,000 individuals of Lophomyrtus bullata before the arrival of the rust Austropuccinia psidii in 2017, for which there currently is no cure. This has led to a 50% reduction in seven years and observations suggest the decline is accelerating, with specimens dying within one month to two years from the time of first infection depending on plant size. In some parts of this species' range it is now close to being extirpated due to this rust. Population decline is measured over a moving window considering c. one generation past and two generations into the future as decline is continuing and likely to be greater in the future due to Austropuccinia psidii (2000–2060). Across this time the population is suspected to experience a decline decline of at least 80%. The species is therefore assessed as Critically Endangered.

This species is endemic to Aotearoa / New Zealand where it occurs on Te Ika a Maui / North Island and Te Wai Pounamu / South Island (Golden Bay, Nelson, Marlborough Sounds and Rarangi). A few scattered records are known from offshore islands of North Island, including on Aotea / Great Barrier Island and Kapiti Island.

The species is widespread in lowland parts of Te Ika a Maui / North Island, with a mostly westerly distribution and scarce in Te Wai Pounamu / South Island. Former strongholds included Tutamoe, Tangihua, northern King Country (Waitomo, Te Kuiti) and the Taranaki.

The estimated population size is more than 500,000 mature individuals in situ. However, this is a reduction from a probable excess of 1,000,000 individuals of Lophomyrtus bullata before the arrival of the rust Austropuccinia psidii in 2017, for which there currently is no cure. This means a 50% reduction in seven years and observations suggest the decline is accelerating, with specimens dying within one month to two years from the time of first infection depending on plant size. In some parts of this species' range it is now close to being extirpated due to this rust. Prior to this time there had been a contraction in the range and population size due to possums.

This species is likely to live for up to 50 years. There is no information available on when the species begins to reproduce. Consequently, a generation length of 20–30 years is given to measure continuing decline. This also reflects that this is a small species of tree. Population decline is measured over a moving window considering one generation past and two generations into the future as decline is continuing and likely to be greater in the future due to Austropuccinia psidii (2000–2060). Across this time the population is expected to experience a decline of at least 80%.

Lophomyrtus bullata is a shrub or small tree reaching six or more metres tall. Between November and March this species may flower, though flowering usually peaks during summer. The black or dark red-fleshed fruits are bird dispersed (de Lange 2023). Lophomyrtus is found in coastal to higher altitude forest and shrubland. It is often a locally conspicuous component of the understory of lowland Podocarp riparian forest. Lophomyrtus bullata also occasionally grows in suitable sites in slope forest, and in wetter areas is sometimes a common component of regenerating shrubland in cut over forest (de Lange 2023).

Undoubtedly there was major range contraction as a consequence of historic forest clearance and animal browsing (especially from possum (Trichosurus vulpecula)) throughout this species' range. Irrespective of these issues Lophomyrtus bullata was considered a widespread, non-threatened common species until the May 2017 detection of the exotic rust Austropuccinia psidii in Aotearoa / New Zealand. This rust causes myrtle rust disease, which kills members of the myrtle family, and Lophomyrtus had already been identified in overseas gardens as highly susceptible (Prasad et al. 2022). As a consequence of the rust's arrival all Aotearoa / New Zealand Myrtaceae were treated as ‘Threatened’ invoking the precautionary principle of Townsend et al. (2008), citing as evidence advice from Australian botanists then in the throes of a decade of witnessing the impact of Austropuccinia (de Lange et al. 2018). At the time of writing (2023) Austropuccinia has now increased its range across Aotearoa / New Zealand, and one of the most vulnerable indigenous myrtles has proved to be both species of Lophomyrtus. Austropuccinia infections were first detected on L. bullata in cultivated plants during May 2017 but soon spread to wild occurrences, and by 2020 widespread death from this rust were being reported from throughout Northland, Auckland, Waikato, Bay of Plenty, Taranaki, and Tairawhiti / East Cape (Prasad et al. 2022). In some parts of this species range it is now close to being extirpated.

This species is commonly cultivated. However, most of the plants sold as this species by commercial nurseries are selections of Lophomyrtus × ralphii – a hybrid swarm that occurs wherever the range of L. bullata and L. obcordata overlap. The bullate, usually strongly pigmented leaves of L. bullata are popular for use in the florist trade. This species, L. obcordata and L. × ralphii are common hedge plants in Aotearoa / New Zealand.

Austropuccinia has severely impacted garden plants and nursery stock, and in Aotearoa / New Zealand, this species is now becoming scarce in the horticultural trade. It is, however, widely cultivated overseas. The seed of this species has short-term viability, so will not store, as it cannot be allowed to dry out, so the species is not well served by seed-banking (Van de Walt and Nadarajan 2023).

The key threat to Lophomyrtus bullata is Austropuccinia psidii. All other known threats can be effectively managed but the rust, so far, has not been. The impact on Lophomyrtus is severe, infections resulting in the death of seedlings, saplings, and mature adults (these within as little as two years). As the rust continues to spread, and infections increase, there will be more spores spread, so the severity in infections of host plants is anticipated to increase. Currently there is no known cure for Austropuccinia, all that can be hoped for is that some lineages of host plants have or develop resistance. To date there has been no evidence for this.

As the rust is wind dispersed quarantine measures are also ineffective. The seed of Lophomyrtus bullata has short-term viability and viability is affected by desiccation and freezing (Van de Walt and Nadarajan 2023), so conventional seed banking is of limited value. Current measures to secure the species should consider holding tissue-cultures. Consideration should be given to cultivating the species outside the global distribution of Austropuccinia, to see if at those sites the species can be secured in Botanic Gardens and other threatened plant collections.

Research into finding a cure for Austropuccinia is a global issue and many organisations are working in this area. Like all research however, those investigations are subject to funding issues and political whim. Austropuccinia is a global problem, a global response is needed – only time will tell if humanity understands the consequences of the loss of the Myrtaceae on world ecosystems and takes the right steps to find solutions to help manage this rust.

New Zealand Threat Classification System assessed this species as ‘Threatened / Nationally Critical’ Qualified ‘DP’ [Data Poor] (de Lange et al. 2018) citing criterion ‘C’ viz., ‘population (irrespective of size or number of subpopulations) with a very high ongoing or predicted decline of > 70%’ – at the time that assessment was done (May 2017) it was precautionary, events have transpired to show it was, unfortunately correct.