The Beeholder, January 2009.

One of the biggest world wide threats to honey bees, the varroa mite, could soon be about to meet its nemesis. Researchers at the University of Warwick are examining naturally occurring fungi that kill the varroa mite.

It is well known that bees world wide are suffering serious declines and one of the causes of that decline is the varroa mite, Varroa destructor. No natural insect or other enemies of varroa species have been identified on the varroa or on their bee hosts. Now Defra-funded studies by Warwick HRI, and Rothamsted Research have found some new natural enemies of varroa from other hosts.
University of Warwick researcher Dr Dave Chandler said: ”We examined 50 different types of fungi that afflict other insects (known as entomopathogenic fungi) to see if they would kill varroa. We needed to find fungi that were effective killers of varroa, had a low impact on the bees and worked in the warm and dry conditions typically found in bee hives. Of the original 50 fungi we are now focusing on four that best match those three requirements.” The fungi typically kill the Varroa mites within 100 hours . ( see picture next page below)

Although the fungi occur naturally the mites rarely encountered them inside hives because honeybees kept their homes so clean. So the challenge is to find a method of introducing a constant supply of the appropriate fungi into the hive . A number of approaches are being considered including having fungal footbaths at the main entrances to hives. However the complex environment within bee hives means that more devious means of application may be needed.

Dr Chandler said the aim was not to eliminate the Varroa mite, but to ensure that populations were kept to very low levels. The fact that the fungal controls kills Varroa by different methods could mean that the mites never develop the kind of resistance that is making pesticides less effective.

Listen to Dr Dave Chandler discussing his work here:
http://www2.warwick.ac.uk/newsandevents/audio/?podcastItem=chandler.mp3

Dr Chandler himself hosted the Society for Invertebrate Pathology’s international conference at the University of Warwick, in August 2008. In the corridors around the Special Session on Honeybee Health the rivalries between research teams from NZ , the USA and Great Britain surfaced. Finding a cure to the world wide Varroa problem is the Holy Grail of the bee health: whoever can get out the first patent for a successful cure will make some very serious money.

New Zealand scientists consider themselves in the forefront having discovered a Metarhizium fungus that kills Varroa but doesn’t affect bees or the honey. Initially it was effective in the lab only, but now HortResearch have developed a delivery system that has shown a 95% kill rate against Varroa in the field. HortResearch is now working with Becker Underwood, an international company based in Australia, to commercialise the product for the beekeeping industry to use.

All research teams are looking at the footbath method of delivering the fungus into the hive. It is this link between Varroa and fungus that can be most easily be patented. However researchers have to be careful not to fall foul of an existing patent on bee footbath. Strangely this patent was (is) for infecting the feet of bees as they leave the hive. “Bee footbaths were originally designed so that bees would take beneficial fungi to flowers”, explains Joseph Kovach, Associate Professor of Entomology at Ohio State University who has a patent on the apparatus. “This idea is the reverse, with spores going into the hive. It is an efficient way to inoculate a hive…the footbaths[allow the bees to carry] the spores on their legs and disseminate them throughout the hive.”

The patented footbath is attached to the entrance of the hive and has been found to be so easy and effective that researchers into bee health are taking out licences to use the method to induce fungi (sometimes with a electrostatic charge) into the hive.

In public most academics deny that there is any holding back of information about bee health but in private most accept that a strong rivalry and secrecy between research teams is holding back the release of an effective cure for varroa. However, we beekeepers should be able to buy an effective fungus based anti-varroa treatment within 5 years ..maybe 10..maybe...

Tony Shaw