Successful restoration of Metrosideros polymorpha (ʻōhiʻa) is possible in forest sites with active Rapid ʻŌhiʻa Death infections

Abstract

Rapid ʻ Ohiʻa Death (ROD), caused by the fungal pathogen Ceratocystis, is killing large numbers of ʻ ohiʻa trees (Metrosideros polymorpha) in Hawaiʻi. ʻ Ohiʻa are a dominant tree in Hawaiian forests, have a range that goes from arid to wet forest climates, and are important for endangered species habitat and ecosystem function. To test whether actively planting ʻ ohiʻa seedlings is a viable restoration strategy in areas with high ROD mortality, we planted ʻ ohiʻa in a ROD-affected forest and crossed this with weeding and fencing treatments to compare ROD mortality to other stressors. We also tested for viable Ceratocystis spores in soils around planting areas. We found that seedlings were more likely to die in unweeded and unfenced treatments than controls. Although viable Ceratocystis spores were found in soil, none of the 41 dead seedlings tested positive for Ceratocystis. This indicates that competition from exotic plants and exotic feral ungulate damage are more likely to kill seedlings than ROD within the first year after planting.

Ceratocystis lukuohia‐infested ambrosia beetle frass as inoculum for Ceratocystis wilt of ʻōhiʻa (Metrosideros polymorpha)

“…Ambrosia beetle frass contains thick‐walled chlamydospores of C . lukuohia , and chlamydospores within the frass particles are probably the propagules that have been detected in soil (Heller & Keith, 2018; Yelenik et al, 2020) and wind (Atkinson et al, 2019) in affected stands.…”

“…lukuohia ‐infested frass into the environment that may then be dispersed by wind and rain‐splash (Roy et al, 2019, 2020). Contaminated frass may also be deposited onto surrounding soils and can be spread elsewhere by animals, including ungulates and humans (Yelenik et al, 2020).…”

“…Attack and gallery development by predominantly non-native ambrosia beetles in trees killed by ROD ejects large volumes of C. lukuohia-infested frass into the environment that may then be dispersed by wind and rain-splash (Roy et al, 2019(Roy et al, , 2020. Contaminated frass may also be deposited onto surrounding soils and can be spread elsewhere by animals, including ungulates and humans (Yelenik et al, 2020).…”

Elevation, canopy cover and grass cover structure patterns of seedling establishment in a subtropical post‐fire restoration

“…The success of this particular relationship has resulted in both on‐the‐ground management and useful publications (e.g. Gill et al., 2018; Hamilton et al., 2021; Warneke et al., 2023; Yelenik et al., 2020). Furthermore, the partnership between government scientists and academic scientists, in our case through the INTERN program of the National Science Foundation (NSF), provided both critical funding and personpower.…”

Ambrosia beetles (Coleoptera: Curculionidae) can directly transmit the fungal pathogens responsible for Rapid ʻŌhiʻa Death

“…However, like other Ceratocystis fungal tree diseases, both C. lukuohia and C. huliohia can be transported in ambrosia beetle (Coleoptera: Curculionidae: Scolytinae) frass (i.e., wood particles, faeces, and beetle parts) (Atkinson et al, 2019;Barnes et al, 2018;Roy et al, 2019Roy et al, , 2020 and enter trees via open wounds created by mechanical means (i.e., feral ungulates, humans, extreme weather events) (Cannon et al, 2022). Frass particles contain long-lived resting chlamydospores (Hughes et al, 2022) and can spread in the wind (Atkinson et al, 2019;Roy et al, 2021), soil (via humans and ungulates; Yelenik et al, 2020), and potentially water (Harrington, 2013).…”