In 1822, European settlers brought honey bees to Australia; two centuries later, scientists found they were spreading a tree-killing plague farther than the wind ever could

Honey bees have long been regarded as one of the most valuable assets to agriculture. Brought to Australia by European settlers in the early 19th century, the western honey bee has long served as an important pollinator of both native species and introduced plants. New research suggests that it may have struck up an unusual alliance with one of Australia's most destructive plant diseases, and the insect could be spreading it further than was thought possible.According to research published in NeoBiota, the Western Honeybee appears to collect spores as a food source of the invasive fungal pathogen Myrtle Rust and then return to its hive with them. Scientists believe this could change their perception of how the pathogen spreads and how susceptible our biosecurity system is.A fungus threatening Australian forestsThe myrtle rust is caused by the fungus Austropuccinia psidii, and was first seen in Australia in 2010.Since then, it has rapidly spread to much of the continent. It affects species in the Myrtaceae family, including paperbarks, eucalypts and bottlebrushes. These plants play a huge part in Australia's ecosystem.Reportedly, hundreds of Australia's native plants are affected by the disease, making myrtle rust a serious threat to biodiversity. Nearly 17% of Australia's endemic vegetation is considered to be under threat from the fungus.Scientists find bees eating spores of the fungusThe traditional thinking is that the fungus will spread primarily through the wind. The University of Cambridge scientists, however, observed western honey bees gathering spores.Their surprise only grew when they discovered how nutritional the spores were.According to the NeoBiota study, rust fungi consist of more than 22% protein, containing all ten essential amino acids necessary for honey bee development. Laboratory tests showed that larvae fed fungal spores as part of their diet did not show problems compared with normal feeding regimes and grew to a comparable size as larvae fed high-quality pollen.It may not have even been an accidental thing, as a study researcher said that this finding suggests the foraging of the fungal spores is perhaps not a random occurrence, but rather a legitimate resource provision strategy that honeybees adopt when alternative food sources are diminished. A troubling discovery inside the hivePerhaps the most significant finding emerged when researchers examined what happened to the spores after they entered bee colonies.The study found that myrtle rust spores remain viable in the hive for at least 9 days. This means the fungal pathogen remains infectious even after collection by honeybees. This is a problem because commercial honeybee colonies are frequently transported across very large distances to pollinate crops.It is common for bees to be transported across the entirety of Australia to aid agriculture. Scientists believe this could result in fungal spores travelling much further than they would do solely via wind dispersal.An Invasive Mutualism between two introduced species emergesThe scientists believe that a cycle is being generated, something called "invasional mutualism."As myrtle rust damages Myrtaceae plants, floral resources may decline, potentially encouraging bees to seek alternative protein sources such as fungal spores. As these flowers have their pollen removed by the bees for food, they, in turn, take spores of the fungus back to their colony.Researchers suggest this could create a feedback loop. The fewer trees, the fewer flowers available and the more bees foraging for food, potentially transporting spores. They believe that this could destabilise plant/pollinator interaction and forest regeneration.This study matters beyond AustraliaEven though the study concerns a problem that only directly affects Australia, the scientists are not surprised when asked to speculate about international ramifications.According to the Australian Government’s Department of Agriculture, Fisheries and Forestry, the western honey bee is one of the most widespread pollinators worldwide, used commercially across Europe, North America and Asia. This research suggests pollinators may play a larger role in plant pathogen dispersal than previously recognised.The authors of the paper are asking that the general biosecurity approach to diseases in flora is to look at the environment around them for infection and look at plants for disease, and forget about the most widely transported animal in the world when constructing future policies and studies into disease control and management.How invasive species can interactIt is a stark warning for environmentalists about how unpredictable species interactions can become when those species are introduced into a new environment.This is a scenario that is likely to be repeated in other biomes around the world, and perhaps that is something that needs to be factored into environmental studies in the future. In this specific case, an insect that has been introduced to Australia for over 200 years has been observed to be a potential vector in the spread of an invasive species for its own food benefit.This does not mean the honey bee will become a threat to the ecosystem; it simply shows us how easily an ecological balance can be destabilised by the introduction of invasive species and human activity.