|Sehgal, Blossom -|
|Subramanyam, Bhadriraju -|
|Gill, Bikram -|
Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2013
Publication Date: April 1, 2014
Citation: Sehgal, B., Subramanyam, B., Arthur, F.H., Gill, B.S. 2014. 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. Pest Management Science. 70(4):576-587. DOI: http://dx.doi.org/10.1002/ps.3580. Interpretive Summary: Residual insecticides are often applied inside grain bins before grains are loaded into the bin or to structural surfaces supporting those bins, and there are questions regarding effectiveness of insecticides on field strains of stored product insects compared to laboratory strains. We exposed different fields strains of some common stored product insects on concrete treated with labeled insecticides, and then placed them on untreated concrete with flour. Insects survived when given food, there was variation among the insecticides regarding effectiveness for control of the field strains, and in general the field strains were harder to kill than comparable laboratory strains. Results show that no single insecticide was completely effective for control of all species and field strains, and application of a specific residual insecticide may depend largely on the intended target species.
Technical Abstract: The efficacy of beta-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 beta-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces and determined knockdown, 7-d mortality, and progeny production. 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. Beta-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. Reduced susceptibility in field strains may be due to inherent formulation deficiency and low levels of tolerance or resistance to beta-cyfluthrin. No single insecticide provided adequate control of the three species tested.