Residual effect of cyanophos(op) on the granary weevil, Sitophilus granaries (l.) and methoprene (igr) on the red flour beetle, Tribolium castaneum (herbst.)

Document Type : Original Article

Authors

1 Department of Pesticides, Faculty of Agric Karr El-Sheikh

2 Department of Plant Protection, Faculty of Agric. Tanta, University of Tanta, Egypt

10.21608/jpces.2000.460485

Abstract

Toxicity of cyanophos was determined by exposure of the adult insects of S. granarius to treated wheat grain. The LC30, LC50 and LC90 values were 8.5, 15 and 150 mg/kg, respectively. The effect of each concentration decreased gradually with the time elapsed and as a result of expanding the exposure time, the mortality percentages increased with each concentration. In general, with the three-exposure intervals tested i.e., 24, 48 and 72 hr., the effect of the LC30 did not continue longer than 40 weeks post-treatment even with the exposure time of 72 hours. The value of LC90 persisted more than both LC50 and LC30 and achieved considerable mortality percentages till 45 weeks post-treatment especially with the exposure time of 48 and 72 hours. So, the longer exposure time of adult insects, the longer persistence of the insecticide. The results cleared that the exposure to residue of LC30 (8.5 ppm) value of cyanophos affected greatly the progeny number of S. granarius and the effect of this concentration extended till 45 weeks post-treatment with percent reduction of the progeny of 58.2%. The residue of LC50 (15 mg/kg) value of cyanophos inhibited completely the progeny number till 15 weeks post-treatment, and also the effect was still clearly high till 45 weeks post-treatment, since the percent reduction was 70.4%. While, with the LC90 (150 mg/kg) value, the percent reduction was 100% in the progeny number till 40 weeks post-treatment, and also the effect was still clearly high and was closely to 100% reduction till 45 weeks post-treatment. In general, as the concentration of the insecticide applied increased as the persistence on the grain prolonged or as the reduction in the insect numbers increased. But when the effectiveness of the (IGR) methoprene was evaluated against larvae, pupae and adults of T. castaneum with different concentrations. There was no appreciable effect of the (IGR) against the pupae or adults. Sequential effects ofthis compound on the last instar larvae were followed until adult emergence. Number of dead larvae increased by increasing the concentration of Methoprene or the time after treatment and maximum mortality was achieved after 28 days. Most of the alive larvae failed to reach to the pupal stage and still alive for a long period. Less developed pupae were observed especially at higher concentrations. Maximum pupation in larvae was achieved after 10 days post-treatment. Obvious suppressing effect of adult emergence in Methoprene treatments (higher inhibition) was obtained at 5 and 10 mg/kg where it was shown as 85.42% and 91.67 % respectively comparing with that in the untreated control.

Keywords

Journal of Pest Control and Environmental Sciences
Volume 8, Issue 1
April 2000
Pages 41-64

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