User tools
Fighting a little bee mite
A little mite, like a tiny spider the size of a pin head, has been plaguing New Zealand’s bee industry for the last few years. The mites, called varroa, are parasites which live on the outside of honey bees and their developing larvae. They feed on the bees and lay their eggs on the larvae, often causing death or deformity to the developing bee. The mites’ activity weakens and kills honeybee colonies. This represents a serious threat to our entire economy because the bees are responsible for pollinating many of our food crops.
The varroa mite is a problem in many parts of the world. No one is sure how it came to New Zealand as it can only be spread from live bees to other bees, and we have not allowed bee imports into this country for more than 40 years. It is likely that the infestation was a result of an illegal import of queen bees from a varroa-infested country, or an accidental import of a bee colony or swarm in a shipping container.
But help for the bees might be at hand, scientists have been investigating a fungus that may well turn out to be the mite's 'worst enemy'. Honeybee researchers at HortResearch have successfully used a strain of the common insect fungus Metarhizium to treat beehives infected with varroa. Metarhizium is a very common fungus that occurs naturally in the environment. Harmless to humans, it is known to infect a large number of insects and has previously been used as a biocontrol for plant pests.
Using the fungus to combat varroa is not new. Previous attempts to develop a commercial Metarhizium-based product have failed because the fungus is rapidly removed from the hive by the bees themselves as part of their normal hive cleaning and maintenance behaviour.
HortResearch honeybee expert Dr Mark Goodwin says his team have solved this problem by finding a way to keep the fungus within the hive at high enough concentrations to achieve mite control.
"It was enormously frustrating. This strain of Metarhizium is varroa's worst enemy. So we had an excellent biocontrol for varroa but were being thwarted by a bunch of very house proud bees," says Dr Goodwin.
"We said to ourselves, 'This is a biological product. We need to stop thinking of it as a pesticide treatment and more as a living organism'. When we did that we found a way to make Metarhizium part of the overall hive ecosystem. The bees accept it, and the fungus is able to get on with killing varroa."
The good news for beekeepers worldwide is that the science can be commercialised and made available in a very short timeframe. HortResearch is now working with an international partner to produce a commercial version of the treatment before the end of the year.