New Hope for Bees
Miss Caroline Birchall has been working on finding a fungus which can infect and kill the varroa mites which afflict our bees.
Without help from
a beekeeper, colonies of bees affected by varroa are overwhelmed by
the pest within four to five years.
“Biological Control of Varroa Destructor” was the title
of the Rosina Clarke Memorial Lecture which was presented by Miss Birchall
in the Miller Hall, Twickenham. The objective of her work is to develop
a new, safe, natural treatment. The work is urgent as treatments that
have been used previously are becoming less useful as mites become resistant
to them. The painstaking scientific methods that are required are essential,
lengthy and time consuming.
There are over 750 species of fungi that infect arthropods (insects, spiders and mites). Fungi infect their hosts when a spore penetrates the insect’s outer cuticle. The fungus grows inside the insect which subsequently dies. The fungal spores may then spread to another host as the insect decays. The task is to find a fungus that will infect and kill varroa mites on bees without damaging bees or the environment, and without contaminating hive products including honey.
Phase
1 of the project ran from 1997 to 2001. Initially all the relevant scientific
literature had to be reviewed and this task alone took over a year. Records
were found of at least 58 species of fungi active against mites. Forty
promising “isolates” or strains of fungi were selected for screening
against varroa.
Fungal spores were applied to varroa mites which were kept on bee pupae
in an incubator. All the isolates killed varroa but at different rates.
Other factors investigated include effectiveness under hive conditions
and possible side effects on the bees themselves and other beneficial
insects. From these results, the best 10 isolates were selected for Phase 2.
Phase 2 of the Project started in 2002 and is anticipated to finish at
the end of 2005. The effects on mites in bee colonies are being examined
along with some key additional factors that are likely to determine the
success of a fungal biocontrol agent such as formulation, suitability
for mass production and persistence under colony conditions. Results so
far are encouraging and next year isolates will be tested against varroa
in a full scale bee colony experiments. The final aim of the project is
to provide a pre-commercial source of information that can contribute
to the registration of a fungal biological control agent against varroa
in the UK
At least 15 biocontrol products involving fungi are already licensed for use against other agricultural pests and there is every hope that Caroline Birchall’s work will lead to a new treatment for varroa. Beekeepers everywhere will be looking forward to hearing about her progress in this valuable work.
Caroline Birchall works for the Plant and Invertebrate Ecology Division, Rothamsted Research. The work is done in collaboration with scientists at Warwick HRI and is funded by DEFRA.
© BUZZ, The Newsletter of the Twickenham and Thames Valley Beekeepers, December 2004
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