Researcher Finds Keys to Cockroach Resistance
By Jim Core
June 5, 2001
An Agricultural Research Service scientist has
identified several key mechanisms responsible for insecticide resistance in one
of the world's most intrusive cockroach species.
Steven M. Valles, an entomologist at the ARS
Center for Medical, Agricultural and
Veterinary Entomology (CMAVE) in Gainesville, Fla., has been studying
strains of the German cockroach (Blattella germanica) to determine how they
develop resistance to insecticides.
Valles identified the role that a previously unknown detoxification enzyme
plays in conferring insecticide resistance in the German cockroach. He
discovered that several strains of the German cockroach possess a unique
membrane-bound substance, called esterase, that detoxifies certain
insecticides. This enhanced ability greatly increases the amount of insecticide
needed to kill cockroaches possessing the enzyme.
In related studies, Valles and Ke Dong of Michigan State University studied what's
called knockdown resistance (kdr), an insecticide-resistance mechanism caused
by mutations in nervous system proteins of some insects. They identified a gene
mutation associated with kdr in 83 percent of German cockroach field
populations they surveyed. The scientists later found two new mutations that
were shown to make the roaches more resistant to pyrethroid and related
Of more than 4,000 cockroach species in the world, only a few--most notably
the German cockroach--dwell in homes. ARS scientists are interested in
controlling cockroaches because they pose a threat to humans by contaminating
harvested crops at processing plants, along with food products in supermarkets
and homes. In addition, cockroaches carry pathogenic organisms that may be
passed on to humans through surface and food contamination. And, cockroach
feces, saliva, eggs and exoskeletons contain substances that are highly
allergenic, especially among people with asthma or other respiratory
According to Valles, the research will be used in future studies to possibly
develop kits capable of detecting insecticide resistance in field populations
of German cockroaches (and possibly other insects). This would allow
exterminators to choose the most effective control methods.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.
Scientific contact: Steven M. Valles, ARS Center for Medical,
Agricultural and Veterinary Entomology, Gainesville, Fla., phone (352)
374-5834, fax (352) 374-5818, firstname.lastname@example.org.