Toxicity, Resistance And Sublethal Effects Of Selected Insecticides On German Cockroaches, Blattella Germanica (L.) (Dictyoptera: Blattellidae) In Malaysia
Loading...
Date
1995-12
Authors
Chow Yang, Lee
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This study which focuses on the German cockroach has dealt with sev.eral
aspects of toxicity, resistance and sublethal effects of selected insecticides.
ThiJteen insecticides (alpha-cypermethrin, beta-cyfluthrin, bencliocarb,
bifenthrin, chlorpyrifos, cypermethrin, cyphenothrin, deltamethrin, etofenprox,
fenitrothion, lambda-cyhalothrin, permethrin and propoxur) were tested topically
against susceptible adult German cockroaches. Lambda-cyhalothrin was the most
toxic compound against both sexes, while propoxur and bencliocarb were least toxic
to male and female, respectively. Intrinsic and extrinsic factors (age,
pretreatment starvation, immobilizing technique, and time of insecticidal
application) were found to affect adult male susceptibility to propoxur; however,
susceptibility to deltamethrin was not dependent on the last two factors.
Insecticide resistance status and the possible .r esistance mechanisms
involved in field German cockroaches in Malaysia were studied for the first time.
Twelve strains collected· from hotels, ·restaurants and naval ships in several
locations in Peninsular Malaysia were te.sted topically for their susceptibility to
insecticides. Resistance levels at LD50 were low to high (2.8- to 91.7 -fold) for
carbamates, low (2.0- to 7.6-fold) for organophosphates and low to moderate (1.0-
to 52.3-fold) for pyrethroids. Five strains were also resistant to DDT. Synergism
studies with PBO and DEF® on ten strains suggested the involvement of
monooxygenases and esterases in propoxur resistance. Cypermethrin and
permethrin resistance were not suppressed when using either synergists.
Four resistant strains were further chosen to chru·acterize the resistance
mechanisms involved using biochemical assays. Elevated esterase (low to
moderate frequency) and altered acetylcholinesterase (low frequency) were
detected in all four strains, while elevated glutathione S-tnmsferase were present
gel electrophoresis, showed a greater banding intensity in Et, Es and E1 bands·in
the resistant strains than in those of the susceptible strain.
Five field strains studied demonstrated longer nymphal development,
preoviposition and incubation periods, lower fecundity and shorter longevity than
the susceptible strain. Susceptible strain had a higher intrinsic rate of increase
(rn) than a field strain, but similar to that of another field strain. Nymphal sexratios,
however, were similar among all strains.
The sublethal effects of deltamethrin, propoxur and chlorpyrifos on adult
longevity and fecundity were studied by reciprocal crossing. The longevity and
fecundity of treated insects reduced with increasing sublethal doses of
deltamethrin and propoxur; however, an inconclusive result was obtained for
chlorpyrifos. Preoviposition and incubation periods were inflependent of the three
insecticides. Both treated females and males showed significant effects on
oothecal hatchability and nymphal production; however, oothecal production was
not dependent on the latter sex. Sublethal doses of.deltamethrin, propoxur and
chlorpyrifos did not result in an increase of insecticidal tolerance in the F1
generation.
Description
Keywords
Biological Sciences , Toxicity