Effect of bio-rational insecticides on some biological aspects of the Egyptian cotton leafworm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

The bio-rational insecticides Dipel 2x, BioFly, Agrin, BioGuard, Spinosad, Neemix, Mectin and Match were tested for their effect on 1^st, 3^rd and 5^th instar larvae and egg masses (24, 48 and 72 h old) of the Egyptian cotton leafworm <i>Spodoptera littoralis</i> under laboratory conditions. The doses used were the recommended dose, half of the recommended dose and quarter of the recommended dose. All insecticides caused higher mortality in the 1st than in the 3^rd and 5<sup>th<sup> larval stage, although Match, Mectin and Spinosad at all tested concentrations showed excellent efficacy against the 3^rd larval stage of <i>S. littoralis</i>. Also, Match resulted in 100% mortality of 5^th instar larvae at all tested concentrations. Moreover, these insecticides also strongly affected some biological parameters of treated 3^rd and 5^th instar larvae of <i>S. littoralis</i>. Egg masses of different ages (24, 48 and 72 h old) where dipped into the recommended dose of each insecticide and the mortality rates determined; eggs of different ages were affected similarly, with mortality rates of 83.4, 85.0 and 71.7%, respectively, after treatment with Spinosad compared to the control. In general, eggs 48 and 72 h old were less sensitive than 24 h old ones. A latent effect of the insecticides on egg hatchability of <i>S. littoralis</i> was observed only in Match and Neemix, with the average being 55.0% and 51.6%, respectively. Our results suggest that Match, Mectin and Spinosad are potentially potent compounds for control of <i>S. littoralis</i>.