Variation in susceptibility of laboratory and field strains of three stored-grain insect species to beta-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces
2014
Sehgal, Blossom | Subramanyam, Bhadriraju | Arthur, Frank H. | Gill, B. S. (Bikram S.)
BACKGROUND: The efficacy of β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to clean, concrete floors of empty bins prior to grain storage against field strains of stored-grain insects is unknown. We exposed adults of 16 strains of the red flour beetle, Tribolium castaneum (Herbst); 8 strains of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and 2 strains of the lesser grain borer, Rhyzopertha dominica (F.), collected mainly from farm-stored grain in Kansas, USA, to β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces and determined knockdown, 7-d mortality, and progeny production. RESULTS: Knockdown and mortality differences among species and strains to the insecticides tested were significant. Mortality of all species was less than that of knockdown, suggesting recovery when placed on food. β-cyfluthrin was effective against R. dominica but ineffective against T. castaneum and O. surinamensis field strains even at four times the high labeled rate. Chlorpyrifos-methyl plus deltamethrin was only partially effective against field strains of the three species. CONCLUSION: Reduced susceptibility in field strains may be due to inherent formulation deficiency and low levels of tolerance or resistance to β-cyfluthrin. No single insecticide provided adequate control of the three species tested.
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