Sophia Smith Robert W. Peck Ellen J. Dunkle Jorden A. Zarders Naiʻa Odachi Ryan L. Perroy Helen R. Sofaer 2025 <div class="item-page-field"><div class="simple-view-element"><div class="simple-view-element-body"><span class="dont-break-out preserve-line-breaks ng-star-inserted">ʻŌhiʻa lehua (<i>Metrosideros polymorpha</i> Gaudich.) is the dominant tree in native Hawaiian forests but is threatened by two pathogenic fungi (<i>Ceratocystis</i> spp.) which cause Rapid ʻŌhiʻa Death (ROD). Understanding the spread of ROD is vital to informing prevention and management strategies. Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) contribute to the spread of disease by releasing contaminated frass into the environment or carrying fungal spores between trees on their bodies. We quantified the abundance of ʻōhiʻa-associated ambrosia beetles and their potential contributions to fungal spread within two study sites experiencing active ROD outbreaks. We established a grid of beetle traps at each site, cultured trap samples for viable <i>Ceratocystis</i>, and compared the spatial distribution of beetle captures with that of ʻōhiʻa trees showing symptoms of ROD. Nearly all captured ʻōhiʻa-associated beetles were <i>Xyleborinus saxesenii</i> (Ratzeburg) or <i>Xylosandrus crassiusculus</i> (Motschulsky), both introduced species that utilize many plant hosts. For both species, abundance was unrelated to distance to the nearest symptomatic ʻōhiʻa tree. However, at one of our sites, <i>Xylosandrus crassiusculus</i> abundance was higher on one side of a fence line, where there were more symptomatic ʻōhiʻa within a denser and more diverse forest. Culturing the collected samples (beetles, water, and debris) produced instances of <i>Ceratocystis</i> viability in samples both with and without ʻōhiʻa-associated beetles, supporting the potential for transmission via frass carried by wind as well as direct transmission by beetles. The community of ʻōhiʻa-associated beetles we captured differed from previous findings at lower elevation sites, highlighting the complexity of beetlemediated fungal infection risk.</span></div></div></div> application/pdf en Hawaiian Entomological Society Abundance of ohiʻa-associated ambrosia beetles in two sites with rapid ohiʻa death outbreaks article