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Insecticide resistance status and mechanisms in Malaysian Blattella germanica (Linnaeus)
1Division of Medical Entomology, Institute for Medical Research, Kuala Lumpur.
Abstract:
The insecticide resistance status of 4 strains of adult male Blattella germanica, viz M (Malacca), E (England), F (restaurant) and K (cafeteria) against malathion and bendiocarb compared with a reference susceptible strain (S) was determined by using a modified WHO bioassay method. The results indicated that all the 4 strains were resistant to the insecticides albeit in different degrees. Resistance ratios for malathion ranged from 1.85-41.07-fold, whereas that of bendiocarb ranged from 1.68-4.83-fold. The biochemical microplate enzyme assays technique employed indicated that the resistance in M and E strains were attributed to acetylcholinesterase insensitivity. Multiple resistance was not detected in any of the 4 strains. Parameters of the identified resistance mechanism correlated well with the observed level of resistance. Agar gel electrophoresis showed that variations in esterase isoenzymes did not confer organophosphate and carbamate resistance to the 4 strains.
Insights
German cockroaches exhibit resistance to malathion and bendiocarb insecticides. Resistance is linked to acetylcholinesterase insensitivity in some strains, with varying degrees observed across different populations.
Area of Science:
- Entomology
- Pest Management
- Biochemistry
Background:
- Insecticide resistance in German cockroaches (Blattella germanica) poses a significant challenge for pest control.
- Understanding resistance mechanisms is crucial for developing effective management strategies.
Purpose of the Study:
- To determine the insecticide resistance status of four German cockroach strains against malathion and bendiocarb.
- To investigate the biochemical basis of observed resistance.
Main Methods:
- Modified World Health Organization (WHO) bioassay method was used to assess resistance.
- Biochemical microplate enzyme assays and agar gel electrophoresis were employed to identify resistance mechanisms.
Main Results:
- All four tested strains (Malacca, England, restaurant, cafeteria) showed resistance to malathion and bendiocarb.
- Resistance ratios for malathion ranged from 1.85-41.07-fold, and for bendiocarb from 1.68-4.83-fold.
- Acetylcholinesterase insensitivity was identified as the resistance mechanism in Malacca and England strains.
Conclusions:
- The German cockroach strains studied exhibit varying degrees of resistance to malathion and bendiocarb.
- Resistance is primarily due to acetylcholinesterase insensitivity, not multiple resistance or esterase isoenzyme variations.
- Findings provide insights into insecticide resistance mechanisms for targeted pest control.