Bee afraid: environmental DNA for varroa detection
Environmental DNA (eDNA) is the new frontier in DNA detection superpowers. It uses small DNA traces from the environment to find out what species are present.
Entomologist Dr John Roberts leads a project researching how to use eDNA from hives and honey for early detection of Varroa mite.
Varroa destructor is the most serious parasite of European Honey Bees globally. The tiny mites attach to a bee’s body and feed on its energy store. This weakens the bee and increases its susceptibility to fatal bee viruses carried by Varroa mite, such as deformed wing virus.
Varroa was detected at Newcastle in New South Wales (NSW) in June 2022. NSW DPI is leading the response, with biosecurity zones restricting beehive movement.
"We’re developing eDNA testing protocols for honey and hive testing in collaboration with the University of Canberra, which will give early warning of varroa infection,” John said.
"In February we visited New Zealand, where varroa has been present since 2000, to trial varroa eDNA surveillance methods on infested hives."
The team has also been analysing the Varroa mite genome to find out more about the incursion in NSW last year.
“With NSW DPI and researchers from the Australian National University, we’ve been analysing whole genome sequence data to trace the source of Varroa mite in NSW,” John said.
The team is also testing the Varroa mites for exotic viruses, in collaboration with NSW DPI.
“Fortunately, our genome sequencing analysis has not detected Deformed Wing Virus (DWV) strains, which means Australia is still free of this high priority pathogen," John said.
“We did find several Varroa mite viruses but these are not known to negatively impact bee health.”
This project is being funded by the Australian Government Department of Agriculture, Fisheries and Forestry, with collaboration from the National eDNA Reference Centre at the University of Canberra, James Cook University, Agriculture Victoria, and the New Zealand Ministry for Primary Industries.
Three cheers for native bees!
The European Honey Bee (Apis mellifera) was introduced to Australia to pollinate crops. It joined around 2000 species of native bees that specialise in pollinating native plants and may also be useful for pollinating crops.
Dr Juanita Rodriguez is a bee and wasp taxonomist at our Australian National Insect Collection.
"We’re especially interested in native bees at the moment due to varroa mite. The current count is 1653 species, plus another 500 or so species that haven’t been scientifically named yet," Juanita said.
"We need more young people to study taxonomy and think about a career with bees.”
Some of Australia’s native bees, like blue-banded bees from the genus Amegilla, are solitary species. Others, like sugarbag bees (Tetragonula carbonaria), are social. Only about 0.6 per cent make honey.
Juanita said very few native bee species have been studied for their ability to pollinate crops.
“We do know native bees are useful pollinators of mango, avocado, apple, tomato, raspberry and macadamia,” she said.
The biggest bee in the world
Wallace’s Giant Bee (Megachile pluto) is the largest bee in the world. Females are up to 38 mm long with a wingspan over 60 mm.
Taxonomist Dr Michael Elias works at our Australian National Insect Collection.
"This species is named after Alfred Russell Wallace, who worked on the theory of evolution with Charles Darwin and collected the first specimen of this bee in 1858," Michael said.
"It lives on a small number of Indonesian islands. Despite being listed as vulnerable, specimens are collected and traded illegally. We hold a specimen that was intercepted by biosecurity officials last year."
Wallace’s Giant Bee can give a giant sting, but doesn’t die afterwards. It doesn’t make giant pots of honey, but it does produce a sort of resin to protect its home.
"It is a bit of a strange bee because the females build hives in termite mounds, taking advantage of the protection afforded by the termite colony," Michael said.
Bees as environmental monitors
Dr Francisco Encinas-Viso is part of the team developing eDNA sampling techniques for surveillance of Varroa mite. He said these methods can be useful for detecting other several pests affecting honey bees, such as small hive beetle, and also monitor flowering vegetation including invasive weeds.
“The eDNA techniques we've developed use bees as environmental monitors. Bees visit an enormous diversity of plants in very large areas, which we can identify by collecting pollen DNA from bees, hives or honey,” Francisco said.
“In Kosciuszko National Park, we analysed pollen DNA collected by pollinators, including bees and flies, to find out which plant species were flowering in the local area and which insect species were pollinating which plant species.
"The amazing outcome of this research is the possibility to track in time and space fine-scale changes in our ecosystems which are particularly relevant to understand the impact of climate change."
Dr Liz Milla, another team member working on surveillance using beehives, led a study published last year. It compared the results of people versus bees in a survey of flowering plants in Canberra.
“We found bees can detect more flowering plants than traditional surveys by people. But the plants detected by bees and people only overlapped by about 25 per cent. This means bees and people working together would give the best results," she said.
Liz and Francisco have also used pollen DNA testing of honey to discover its provenance and floral composition.
Pollen DNA can also be used monitor for plant pathogens, such as in avocado orchards. Bee surveillance offers earlier detection of plant viruses than conventional monitoring methods. It also allows surveillance of multiple plant pathogens at once and even pathogens affecting bees themselves.