Ovicidal and larvicidal activity of spinosad against egyptian cotton leafworm | ||
| Journal of Pest Control and Environmental Sciences | ||
| Volume 18, Issue 1, 2010, Pages 69-81 | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jpces.2010.459109 | ||
| Authors | ||
| Shebl M. Sherby* 1; Hamdy K. Abou-Taleb2; Nabil M. Mansour1 | ||
| 1Pesticide Chemistry Dept., Fac. of Agric., Alexandria Unversity, El-shatby, Alexandria,Egypt | ||
| 2Plant Protection Research Institute, ARC, Bacous, Sabahia, Alexandria Egypt. | ||
| Abstract | ||
| One of our objectives in this investigation is to determine the ovicidal action of spinosad (Tracer) and triflumuron (Alsystin®) compared to chlorpyrifos (Dursban®) against 0-1 day old eggs of cotton leafworm, Spodoptera littoralis. The residual toxicity of these insecticides to the neonates is also evaluated. Toxicity of spinosad against 2 instar larvae of S. littoralis by dipping technique and against the 4th, and 3rd instar larvae by topical application was carried out. The joint toxic action of spinosad with cypermethrin, chlorpyrifos and methomyl against 4th instar larvae of S. littoralis was also studied. Spinosad has an ovicidal activity lower than chlorpyrifos and triflumuron. Although spinosad has low ovicidal activity, it has the highest residual activity against the neonates after 24h of hatching. Spinosad has the highest total mortality (% killed eggs + % neonate mortality after 24h of hatching) compared to chlorpyrifos and triflumuron. According to the LC50 values, susceptibility of S. littoralis larvae to spinosad is decreased considerably as the larvae advance in age and weight. Second instar larvae were more susceptible to spinosad than the 3th instar larvae which were more susceptible than the 4th instar larvae. The LC50 values by dipping technique were 41.7, 138.1 and 196.7 ppm for 2ed and 4th, 3rd instar larvae, respectively. Toxicity of spinosad by topical application is enhanced by increasing the exposure time where LD50 values were 0.51, 0.12 and 0.09 g/mg body weight after 24, 48 and 72h of treatment, respectively. Data revealed that dipping treatment exerts toxicity more than the topical application. In respect with the joint toxic action, the combination of spinosad and cypermethrin results in a synergistic effect or an additive effect as calculated by the co-toxicity factors. The combination of spinosad with chlorpyrifos or methomyl results in additive effect or antagonistic effect; this will shed some lights on the possible joint toxic action and the sequence of alternative spraying programs. | ||
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