الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
Cotton leaf worm, Spodoptera littoralis is a serious polyphagous insect pest having a wide host range. Heavily intensive use of traditional insecticides were unavoidable, but it created many environmental problems. So, searching for more safe alternatives became more necessary. Plant extracts were among the promising green alternatives to be used for this aim. The current study aimed to assessment the insecticidal activity of Euphorbia pulcherrima extracts against different stages of S. littoralis. This aim was scored through chemical studies which comprised extraction of the chemical constituents of E. pulcherrima aerial parts then characterization and identification of the volatile components of E. pulcherrima different fractions by using GC/MS technique. The ovicidal, insecticidal and pupicidal activity of different fractions were assessed. Also, biochemical studies which determined the disruption effects of these extract fractions on the transaminases and alkaline phosphatases in S. littoralis were illustrated. The major results of this study can be summarized as follow: 1. Chemical Study: 1.1. Study of Petroleum ether fraction of Euphorbia pulcherrima The GC/MS chromatogram characterized six compounds. Diterpenes compounds [Phytol (80.03%) Neophytadiene (7.07)] and triterpene [squalene (1.05%)] were the major constituents of Pet. ether fraction. In addition, anethole (8.08%), fatty acid, n-Hexadecanoic acid (1.51%) and its ester, Hexadecanoic acid, methyl ester (1.41%). 1.2. Study of methylene chloride fraction of Euphorbia pulcherrima The GC/MS chromatogram showed 22 peaks corresponding to 22 compounds illustrated in table 2. 1.3. Study of ethyl acetate fraction of Euphorbia pulcherrima Ethyl acetate fraction was subjected to GC/MS technique to characterize their volatile components. It gave seven compounds showed in table 3. 1.4. Study of butanol fraction of Euphorbia pulcherrima The GC/MS chromatogram revealed presence of 14 volatile compounds as shown in Table 4. 2. Bioassay Study: 2.1. Ovicidal activity of different fractions of E. pulcherrima extract on S. littoralis eggs: All the tested fractions of E. pulcherrima extracts have significant ovicidal activity against S. littoralis eggs. Petroleum ether fraction was the most efficient followed by methylene chloride fraction, methanol extract, ethyl acetate fraction, then, butanol fraction with LC50: 591.14, 686.18, 1273.63, 1678.76 and 3041.70 ppm, respectively. Also, S. littoralis egg masses hatchbility was absolutely suppressed at 10000 ppm of Petroleum ether, methylene chloride and methanol fractions and at 20000 ppm of ethyl acetate and butanol fraction. 2.2. Efficiency of different fractions of E. pulcherrima extract on S. littoralis larvae: 2.2.1. Efficiency of different fractions of E. pulcherrima extract on S. littoralis 2nd instar larvae: Petroleum ether fraction was the most efficient against the S. littoralis 2nd instar larvae followed by methylene chloride fraction, methanol extract and butanol fraction with LC50 of 207.98, 224.04, 308.99, 619.91 and 899.54 ppm, respectively. It was noticed that all extracts exhibited antifeedant effect making the treated larvae stop feeding, shrank and lost its body weight. By time, the body turned to more dark. 2.2.2. Efficiency of different fractions of E. pulcherrima extract on S. littoralis 4th instar larvae: Petroleum ether fraction showed the highest potency against the S. littoralis 4th instar larvae, followed by methanol fraction, ethyl acetate fraction, methylene chloride fraction, and butanol fraction with LC50: 859.91, 922.54, 1291.97, 2515.79 and 2828.34 ppm, respectively. Abnormal pupation before the normal time resulted in malformed pupae was the most obvious symptom. 2.3. Efficiency of different fractions of E. pulcherrima extract on S. littoralis pupae: Petroleum ether fraction still record the highest efficacy also against S. littoralis pupae, followed by methanol extract, ethyl acetate fraction, chloride fraction, and butanol fraction with LC50s: 3004.44, 3932.12, 3984.94, 5904.67 and 6420.25 ppm, respectively. 3. Biochemical Study: 3.1. Effect of different fractions of E. pulcherrima extracts on transaminases activity of S. littoralis 4th instar larvae: Data indicated that all extract fractions except ethyl acetate fraction, at sub-lethal concentration (LC25) exhibited a great decrease in GPT activity comparing with the control at first three days post treatment. At 5th day post treatment, almost all fractions revealed a significant increase in GPT activity. Methylene chloride fraction recorded the highest value reaching 542.91% more than the control. Also, the inhibition of GOT activity almost along the experiment period was the dominant feature of all extract fractions at sub-lethal concentration (LC25). Ethyl acetate and methylene chloride fractions were the except whereas ethyl acetate fraction exhibited huge increase of GPT activity at the 1st day post treatment, reached to 443.37% more than control, followed by methylene chloride fraction recording 86.51%, then, GOT activity inhibited again. 3.2. Effect of different fractions of E. pulcherrima extracts on alkaline phosphatase activity of S. littoralis 4th instar larvae: Petroleum ether fraction revealed significant inhibition of AlP activity along the experiment period, recording a great inhibition (-77.45%) less than control. On the other hand, ethyl acetate fraction caused highest elevation of the enzyme activity at the third day post treatment reaching 74.07% more than control, then the enzyme activity declined at 5th and 7th day post treatment. It was noticeable that, the other extract fractions at sub-lethal concentration (LC25) revealed a great fluctuation in AlP activity comparing with the control. from previous results, petroleum ether fraction of E. pulcherrima aerial parts extract was recommended as green alternative for controlling different stages of S. littoralis. Every day, the plant extracts prove their worth as promising eco-friendly tool for controlling the plant pests.