Virus replication can be induced most effectively in the laboratory by the injection of foreign proteins, and substances introduced into the haemolymph of bees during mite feeding, such as components of mite saliva, may have similar effects in nature. It is investigating the relationship between mite populations and virus incidence, to determine the critical density of mites and the time of year that damage due to associated infection occurs. The effectiveness of acaricide treatment in limiting mite population development and virus incidence, and the timing of treatment will also be evaluated to provide beekeepers with soundly based practical advice. In addition, there is growing evidence that populations of mites resistant to tau-fluvalinate, the active ingredient of Apistan have appeared. This has raised the question of using biological control methods, but unfortunately no naturally occurring pests or pathogens specific to V. jacobsoni have so far been identified.
Mites are however, known to be susceptible to a range of fungi and bacteria.
This is being carried out jointly by IACR-Rothamsted and HRI Wellesbourne, and has enabled the appointment of an additional graduate scientist at each site. Approximately 100 strains will then be screened for their effectiveness against V. jacobsoni. Once useful strains are identified, they will be tested for their effects on beneficial insects including of course the honey bee, but also ladybirds, predatory mites, and representatives of the other important insect orders. It will then be necessary to study the physiological characteristics and epidemiology of such useful strains, in order to determine their persistence and spread in the hive and in the field, and finally to develop suitable methods for their application within the hive. Whilst there is a risk that a suitable biocontrol agent, which is effective against V. jacobsoni but is harmless to honey bees and other beneficial arthropods, may not be identified within the four years of the project, the potential benefits are considerable.