Field persistence of some insecticides on okra leaves as determined by cotton leafworm (Spodoptera littoralis) bioassay | ||
| Journal of Pest Control and Environmental Sciences | ||
| Volume 14, Issue 1, June 2006, Pages 43-57 PDF (837.82 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jpces.2006.460115 | ||
| Author | ||
| Mohamed M. Azab* | ||
| Plant Protection Dept., Faculty of Agric., Moshtohor, Banha University | ||
| Abstract | ||
| A field experiment was conducted in Moshtohor, Kalubia, Egypt during the summer season of 2004 to study the persistence of spinosad, abamectin, azadirachtin, Dipel 2X and methomyl on okra (Abelmoschus esculentus L. ev. Balady) leaves. The persistence toxicity was determined on the 2nd instar larvae of the laboratory strain of Spodoptera littoralis (Boisd.). The tested insecticides were applied with recommended field rate at 180 gm (28% ai) / feddan, 120 ml (1.8% ai) / feddan, 600 ml (0.15% ai) / feddan, 200 gm (Bacillus thuringiensis subsp. Kurstaki 32000 IU/mg) / feddan and 300 gm (90% ai) / feddan for spinosad, abamectin, azadirachtin, Dipel 2X and methomyl, respectively. The results revealed that spinosad was highly toxic to larvae compared to the other tested insecticides. The LC50 values were 0.4, 1.1, 1.4, 3.1 and 220.8 µg/ml for spinosad, azadirachtin, abamectin, and Dipel 2X, following 72 hr, respectively. In case of methomyl, it was 3.1 mg/ml after 24 hr. The residual toxicity of spinosad, abamectin, azadirachtin and methomyl was sustained up to 10, 7, 5 and 5 days, respectively, while Dipel 2X showed no activity after 3 days of application. The half-life values of the applied insecticides were 1.90, 1.87, 1.40, 0.77, 0.40 day for azadirachtin, abamectin, spinosad, methomyl and Dipel 2X, respectively. | ||
| Keywords | ||
| Insecticides; Abelmoschus esculentus; Spodoptera littoralis; residual toxicity; half-life | ||
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