Insecticidal efficacy of diatomaceous earth against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Laboratory bioassays were carried out to evaluate the insecticidal efficacy of SilicoSec? against 7 - 14 day old adults, old and young larvae of Tribolium castaneum (Herbst) with the mean ? SE (n = 30) weight of 3.4 ? 0.1 and 0.6 ? 0.1 mg, respectively at 27?C and 55 ? 5% RH. Wheat treated with four dose rates of SilicoSec? and untreated wheat served as a control with three replications. Adult?s mortality was measured after 2, 7 and 14 days of exposure. After 14 day mortality counts, all adults were removed and samples retained under the same conditions for a further 60 days to assess progeny production. In the case of larvae, mortality was counted after 1, 2 and 7 day. After 2 day no concentration achieved 11% mortality for adults, however; adult's mortality exceeds 89.65% when exposed for 7 day to SilicoSec?. Mortality of old and young larvae at 600 ppm after 2 day were 28.88 and 22.22%, respectively and exceed to 60.71 and 69.04% at longer exposure of 7 day. Due to results mortality of T. castaneum was influenced by interval exposed to wheat treated with SilicoSec? and over this exposure, the increases in application rate of SilicoSec? had significant effect on the mortality. Young larvae of red flour beetle were more sensitive to SilicoSec? than old larvae and adults were more tolerant. The mean number ? SE of progeny in the control was 1.66 ? 0.101 individuals per vial and there was a significant difference between treated and untreated wheat, so reproductive potential of adults in treated wheat was suppressed when compared with untreated wheat.
 
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