Europe PMC · 2026-04-13
Researchers identified the fungal causes of a damaging macadamia flower disease called rachis tip dieback (RTD), finding that multiple fungal species — not environmental stress alone — are responsible for killing the flower stalks that macadamia nuts grow from.
Three fungal species — Neopestalotiopsis maddoxii, N. macadamiae, and Epicoccum italicum — were confirmed as the primary causes of rachis tip dieback through infection experiments, with Neopestalotiopsis being the most commonly isolated genus (27.5% of samples).
20 different fungal genera were identified from 307 diseased flower samples across 20 commercial orchards in Australia during the 2023 and 2024 flowering seasons.
Two fungal groups, Diaporthe and Epicoccum, are reported for the first time as pathogens of macadamia flower clusters, expanding the known disease complex.
