Improvement of expired insecticides and their effectiveness against the cotton leafworm, Spodoptera littoralis (Boisd.)

Objectives: This study aimed to recycle some expired insecticides and evaluate their effectiveness against the cotton leaf worm, Spodoptera littoralis (Boisd.) as a tactic to dispose of these obsolete insecticides. Methods: The physical and chemical characteristics of chlorpyrifos (Chlorzane 48% EC), malathion (Nasr-lathion 57% EC) and cyhalothrin (Lambda-cyhalothrin 5% EC) insecticides were determined. The active ingredients of the tested compounds were estimated by gas–liquid chromatography (GLC) equipped with a flame photometric detector GC/FPD and the insecticidal efficacy against the 4th instar larvae of the cotton leafworm, S. littoralis (Boisd.) was evaluated by the leaf dipping technique. Results: The physical and chemical characteristics of the tested insecticides clarified that chlorpyrifos (Chlorzane 48% EC) succeeded in the stability of emulsion, while cyhalothrin (Lambda-cyhalothrin 5% EC) and malathion (Nasr-lathion 57% EC) failed the test, whether unexpired or expired. The emulsifiers, Tween 80 or Triton X-100 at a concentration of 20%, managed to improve the characterizations of the expired insecticides, cyhalothrin and malathion. Moreover, these emulsifiers investigated a promising increase in the efficiency of expired cyhalothrin against S. littoralis. Conclusions: The emulsifiers, Tween 80 or Triton X-100 could be used to increase the efficiency of expired insecticides, especially cyhalothrin 5% EC, thus managing to apply and dispose of that outdated insecticide.