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 was 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.