Honeybees May Be Helping Spread Tree-Killing Myrtle Rust – New Research

Why It Matters

Myrtle rust threatens iconic native trees and multi‑million‑dollar horticultural sectors; bee‑mediated spread could accelerate losses and complicate containment efforts.

Key Takeaways

• Honeybees transport live myrtle rust spores on bodies and in pollen stores.
• Spores remain viable in hives for at least nine days.
• Bee larvae grow equally well on spores as on pollen.
• Hive relocation can move disease far beyond original outbreak zones.
• Managing bee movements may curb spread of this forest‑killing fungus.

Pulse Analysis

Myrtle rust, a fungal pathogen native to Central and South America, first appeared in New Zealand in 2017 and has since ravaged native myrtaceous species such as pōhutukawa, rātā and mānuka. In Australia the disease has already driven several native plants toward extinction and cost the nursery and lemon‑myrtle industries millions of US dollars in lost production and management. The economic and ecological stakes are high, prompting researchers to look beyond wind‑borne spores for additional dispersal pathways.

A recent study by Shin‑Clayton and Beggs demonstrates that honeybees inadvertently become vectors for myrtle rust. By comparing spore composition to common pollen, the team showed that spores provide essential amino acids, allowing bee larvae to develop normally when fed spore‑laden royal jelly. Field sampling revealed spores on roughly 50% of foragers returning from infected sites and stored in pollen cells, where they stayed viable for at least nine days. This creates a hidden reservoir within hives, turning managed colonies into mobile carriers capable of moving the pathogen across landscapes.

The implications for biosecurity are immediate. Beekeepers routinely transport hives to follow mānuka blooms or crop pollination, a practice that could unintentionally seed new rust outbreaks in untouched forest reserves. Introducing stand‑down periods before moving hives from high‑risk zones, coupled with routine spore testing, could mitigate this risk. The research also highlights a classic case of invasional mutualism, where an introduced pollinator and an invasive fungus benefit each other. Understanding and managing this relationship will be crucial for protecting New Zealand’s native forests and the multi‑billion‑dollar agricultural economy that depends on them.