Honeybees have a lot going against them; insecticides, land clearance, monoculture, lack of genetic diversity, changing weather, the varroa honeybee mite and, more recently, Colony Collapse Disorder (CCD). It’s not clear what CCD is, whether it’s one virus, several viruses or a host of different factors. Whatever the case, honeybees are key pollinators and we need them.
New Zealand bees are in reasonable health, and haven’t been affected by CCD, which is affecting the honeybees in Europe and North America. But they are still living with varroa, and only this September several hives in Canterbury were found to be infected with the deadly mite.
The varroa mite lays its eggs inside the brood cells of a beehive, where the mites grow up feeding on bee larvae.
Left unchecked, varroa can destroy a hive within a year. It is currently controlled by miticides, but this is only a temporary solution; overseas honeybees are already building up resistance.
New Zealand scientists have been looking for more enduring solutions, and have recently developed an organic bio-miticide. The active ingredient is Metharizium sp., a fungus that is lethal to many insects, including varroa mites, but doesn’t harm bees. Until recently attempts to use it have failed, because the bees are so adept at detecting and eradicating any alien organisms (except perhaps varroa) they quickly clean the Metharizium out. But HortResearch has found a way to stop the bees from doing this. The discovery has been patented and is currently being developed for commercial release, hopefully by autumn.
Meanwhile, HortResearch’s Michelle Taylor is continuing research on varroaresistant honeybees. This has involved chasing a gene that somehow—scientists aren’t sure how—renders the mites unable to reproduce. But as the trait is additive (more than one gene influences the trait), it’s quickly diluted by queens mating with drones that don’t carry the gene. Scientists have therefore been artificially inseminating queen bees in the lab. Again, this isn’t a long-term solution, as it’s too expensive and time-consuming to service New Zealand’s 344,000 commercial beehives.
Taylor is therefore trying to establish a self-sustaining population of high-resistance queens on Great Mercury Island, away from non-resistant honeybees. At the end of last year, HortResearch took 40 hives out to the island, each containing up to 60,000 bees and a queen cell that had been raised from stock that was 80 per cent resistant to varroa. Taylor discovered that while varroa still prevailed in 38 of the hives, two developed 80 per cent resistance. “It’s awesome,” she says. “Eighty per cent was the upper limit of what we’re hoping for, but now we’re trying to push it up to 100 per cent.”
If the experiment is successful, the island could become a vital breeding centre for large numbers of highly resistant queens, providing a gene pool that can be fed back into honeybee populations on the mainland.