|Ghazanfar, M. Usman|
Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2012
Publication Date: 1/2/2013
Publication URL: http://handle.nal.usda.gov/10113/57369
Citation: Wakil, W., Riasat, T., Ghazanfar, M., Lord, J.C. 2013. Effects of combined thiamethoxam and diatomaceous earth on mortality and progeny production of four Pakistani populations of Rhyzopertha dominica (Coleoptera: Bostrychidae) on wheat, rice and maize. Journal of Stored Products Research. 52: 28-35. http://dx.doi.org/10.1016/j.jspr.2012.09.002. Interpretive Summary: The lesser grain borer is a major pest of stored grains, and insecticides are used for its control. But, new insecticides, or combinations of insecticides, are needed because the lesser grain borer has developed resistance to some of those that are currently used. Diatomaceous earth (DE) is a reduced-risk insecticide composed primarily of fossilized diatoms. Thiamethoxam is an insecticide with low mammalian toxicity that is a recent addition to the tools for control of stored-grain pests. We tested these materials separately and in combination for control of lesser grain borers in stored wheat, corn, and rice. Survival and progeny production were lower in wheat than in rice or corn. The insecticides generally were more effective when used in combination than individually. Lesser grain borers from four locations showed differences in susceptibility to the insecticides. This information will be useful to storage managers in selecting tools to combat lesser grain borers and delay resistance development.
Technical Abstract: Bioassays were conducted to evaluate the effects of combining thiamethoxam at 0.25, 0.5 and 0.75 mg/kg with the diatomaceous earth (DE) formulation, SilicoSec, at the rate of 100 mg/kg against four diverse populations of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) that originated from Faisalabad, Toba Tek Singh, Jhang and Bahawalpur districts of Punjab, Pakistan. The tests were carried out with adult beetles on wheat, maize, and rice. Mortality increased with increasing application rates and exposure intervals for each population. Individually, thiamethoxam was more effective at the high dose rate compared with DE alone, and there generally was greater mortality in wheat than in rice or maize. In general, the most tolerant population to any treatment was that from Bahawalpur region, while the least tolerant was from Toba Tek Singh. Production of adult progeny taken over all treatments was significantly greater for the Bahawalpur and Faisalabad populations than for the Toba Tek Singh and Jhang populations.