Impact of some Essential Plant Oils and Insect Growth Regulators on Immature Stages of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) in Egypt

Abstract

The cotton leafworm Spodoptera littoralis (Boisd) (Lepidoptera, Noctuidae) is consider a polyphagous pest infesting cotton and some important vegetables and field crops in Egypt. The latent effects (LC25) of three insect growth regulators (IGRS); Runner (24% SC), Virtu (5% SC) and Roxy (10% EC) and three essential plant oils; coriander, basil and mustard oils were evaluated against fourth larval instar until adult emergence and oviposition under laboratory conditions. The influence of LC25 of tested materials on some biological aspects, nutrition indices for cotton leafworm were evaluated. Novaluron (roxy) showed a great ovicidal activity where recorded the lowest number of laid eggs (611 eggs) compared to control and coriander oil (1103.3 and 871 eggs, respectively). Also, novaluron was the most female oviposition deterrence (23%) and had the highest sterility (68.9%). On the other hand, there was a significant differences between novaluron and tested oils in sterility. Coriander oil recorded the highest feeding deterrence index (FDI) against fourth larval instar which statistically different with all tested treatment, while, tested IGRs had the lowest effect as a feeding deterrent for larvae varied between 7-9%. Relative growth Rate (RGR) had insignificantly varied between tested treatments. Larval duration was significantly elongated when larvae fed on treated castor bean leaves with coriander oil reach to 16.2 days compared to control (13.8 days). While IGRs treatments recorded that shorter larval duration rather than coriander oil, but significantly similar to control. Chromafenozide (virtu) pesticide had the highest larval mortality compared to control and essential plant oils treatments.