The toxicity of benzothiazole derivatives obtained from 2-cyanomethyl benzothiazole against cotton leafworm Spodoptera littoralis 2nd and 4th instar larvae has been documented. The main objective of this research was to formulate two previously reported chromen derivatives and test their biological activity against cotton leafworm S. littoralis 2nd and 4th instar larvae under laboratory conditions. According to the standard method, two chromen derivatives with two distinct substituents (salicylaldehyde and 2-hydroxy-1-naphthaldehyde) were synthesized. Their physical and chemical properties were evaluated, and both were formulated as 10 and 9.5 percent dustable powder formulations. Both formulae were then evaluated in the laboratory on cotton leafworm S. littoralis 2nd and 4th instar larvae for mortality and developmental effect percentage. Formulation (F2) was more efficient than formulation (F3) in both cases and for both stages. Furthermore, when comparing the developmental effects on the 2nd and 4th instar larvae, the 4th instar larvae demonstrated marked tolerance. Both stages were unable to complete their life cycle. Histopathological analysis of samples from the affected stages was performed to assess the mode of action of these formulations on 4th instar larvae at their LC50 values. Experimental data showed that Formulation (F3) resulted in epidermal cells separated from the cuticular layer, necrosis, ruptured columnar cells with pyknotic nuclei, disrupted basement membrane, and weak epicuticle necrosis and separation. In comparison, formulation (F2) revealed a midgut with vacuoles, damaged columnar, muscle cell necrosis, and a ruined peritrophic matrix. Thus, the cotton leafworm S. littoralis could be combated with the newly prepared formulations (F2) and (F3).

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Three compounds of benzothiazole were synthetized as active ingredient and prepared as 10 % suspensions concentrate (SC). They were evaluated against the second and fourth instar larvae of the cotton leafworm S. littoralis (Boisd.), under laboratory conditions. LC50 values showed that formulation (1) gave the highest toxic effect against 2 nd and 4 th instar larvae after 48 hrs from treatment and gave the best effect as antifeedant followed by formulation (3) and formulation (2). Semi field experiment was done to evaluate the initial and latent effects of the formulated compounds compared with commercial insecticide chlorpyrifos 48% EC (Dursban), the results showed that formulation (1) gave 100 % prevention of adult emergency due to the high initial and latent effects and lowest pupation percentage as the same as chlorpyrifos followed by formulation (3) and formulation (2) with the 2 nd and the 4 th instar larvae. Whereas Formulation (1) at 1 % is already as the same of recommended insecticide chlorpyrifos, therefore it could be recommended to use the new formulations as alternative of hazard conventional insecticides in controlling cotton leafworm in different crops after conducting the other necessary open field experiments.