Commercial insectaries that produce wasps as
biocontrol agents will benefit from new Agricultural Research
Service (ARS) findings showing that killing fly pupae—the food
source for the wasp larvae—with heat shock is an affordable
alternative to irradiation. The heat shock alternative will help
insectaries meet fluctuating demand for two parasitic wasps used to
control filth flies.
House flies and stable flies are nuisances on livestock and
poultry farms, and they transport disease-causing organisms.
Parasitic wasps released as biocontrols can reduce the need for
insecticides on livestock and poultry farms.
Wasp species such as Muscidifurax raptor and Spalangia cameroni
lay a single egg inside a fly puparium before it hatches, and the
larva feeds on the fly pupa before emerging as an adult. But it
takes one week to produce fly pupae for the parasitoids, and these
live pupae only have a shelf life of two to three days. So
insectaries turned to ARS for help.
Entomologist Christopher J. Geden of the ARS Center for Medical,
Agricultural, and Veterinary Entomology in Gainesville, Fla.,
studied fly pupae killed with gamma irradiation, cold and heat shock
for their ability to produce parasitoids.
Researchers have reared parasitoids with irradiated pupae for
years, but it's not practical for commercial insectaries. Previous
results from freeze-killing pupae have been mixed. Heat shock
killing in an oven had never been tried before.
The number of wasp progeny, male or female, emerging from pupae
killed by heat shock or gamma irradiation was not significantly
different from those produced on live hosts.
Geden found heat-killed, irradiated and freeze-killed pupae
stored in refrigerated plastic bags remain as effective for
production of M. raptor as live pupae for as long as four
months.
Production of S. cameroni on heat-killed and irradiated pupae was
equal to parasitoid production on live pupae for up to two months of
storage. After that, production declined to 63 percent of live
pupae. Production of S. cameroni on freeze-killed pupae was about 75
percent of production using live pupae for eight weeks of storage
but declined rapidly afterward.
ARS is the U.S. Department of Agriculture's chief scientific
research agency.
Editor's Note: The original news release can be found here.