Two naturally-occurring strains of
the fungus Beauveria
bassiana have potential as
biological control agents for both house fly and stable fly. These
strains were originally isolated from field-collected house
flies. The two fungal strains
in two different
formulations, a dust and a water solutionwere tested against adult
house and stable flies. The spores were applied to plywood
surfaces and the adult flies were exposed to the treated surfaces
for three hours. Fly mortality occurred within 7 days of exposure
to either strain. The dust formulation was better than the wet
formulation in causing infection and mortality. House flies were
killed at most of the dosages tested, while stable flies were not
as susceptible. In these studies fungal virulence (the ability to
infect and kill flies) decreased with time, so repeated B.
bassiana applications may be necessary to achieve good adult
fly control.
Since house flies readily breed in animal bedding, B. bassiana was also tested against house fly larvae in manure and sawdust bedding mixtures. Fungal spores were thoroughly mixed with larval medium (fresh cow manure, sawdust bedding and water), then fly larvae were added to the medium. However, the fungus was only marginally effective against the larvae, and only at high doses.
Adult flies normally rest on the walls and ceilings of dairy barns, so treating building surfaces may be a convenient way to reduce fly populations. Such applications would also reduce the chance of exposing beneficial insects to the spores (B. bassiana also kills fly pupal parasites and probably other natural enemies). However, dust formulations (that worked best in these experiments) do not stick to vertical surfaces very well. Further studies to improve formulations for application to vertical surfaces are necessary before B. bassiana could easily be used as a biological control agent of flies.
Source:
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