The aim of the present work is to investigate the relationship between oviposition of Spodoptera littoralis (Boisd.) and larval frass extracts as well as to assess the electrophysiological effect on tarsus sensilla. The obtained data revealed that oviposition was significantly deterred by frass extract taken from larvae reared at high densities. However with low densities (small groups larvae) the inhibition effect of larval frass was not significant. On the other hand, the minimum concentration of frass extract (with which the leaves were sprayed) to cause significant oviposition deterrence was ranged from 5-10 % in case of Nerium oleander leaf. A petroleum ether extract of larval frass was highly deterrent, as compared with water, ethanol or acetone extracts. Moreover, contact chemoreceptors on tarsus (sensilla chaeticum) plays an important role to find out a suitable place of mated femles moths for egg laying. |
