Insecticidal properties of plant extracts and monoterpenes towards the fourth instars of Spodoptera littoralis Boisd (Lepidoptera: Noctuidae) and adults of Aphis fabae L. (Hemiptera: Aphididae)

Document Type : Original Article

Authors

1 Department of Pesticide Chemistry, Faculty of Agriculture, Alexandria University, 21545-El-Shatby, Alexandria, Egypt

2 Department of Pest Control and Environmental Protection, Faculty of Agriculture (Damanhour), Alexandria University, Damanhour, Egypt

10.21608/jpces.2010.459116

Abstract

The extracts of three plants, namely Zygophyllum coccineum L., Majorana hortensis (Moench) and Mentha microphylla L. were tested for their insecticidal activity against the fourth instar larvae of the Egyptian cotton leafworm, Spodoptera littoralis and the adults of the bean aphid, Aphis fabae. All of the tested extracts were found to be toxic against both insects. However, the degree of toxicity was varied based on plant extract, plant species and insect species. Among the tested extracts, petroleum ether extract of M. hortensis (LD50 = 2.76 μg/larva) was the most potent against S. littoralis followed by chloroform extract of the same plant (LD50 = 3.36 μg/larva). The petroleum ether and ethanol extracts of Z. coccineum showed the less activity against S. littoralis. In the case of A. fabae, the petroleum ether and chloroform extracts of M. hortensis, the petroleum ether and ethanol extracts of M. microphylla showed pronounced toxic effect with LC50 values of 2.21, 2.44, 2.62 and 2.25 g/l, respectively. The essential oil of M. hortensis was isolated by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). Terpinen-4-ol (30.0%), γ-terpinene (11.3%), and trans-sabinene hydrate (10.8%) were the major components of the oil. This oil revealed remarkable insecticidal activity
against S. littoralis and A. fabae. Repetitive column chromatography of the essential oil of M. hortensis led to isolate the two major constituents (terpinen-4-ol and γ-terpinene). The structure of these compounds were determined based on their spectral data of C NMR and MS. γ-Terpinene was more toxic than terpinen-4-ol towards S. littoralis and A. fabae. The isolated compounds were less toxic than the essential oil against both insects. 

Keywords

Journal of Pest Control and Environmental Sciences
Volume 18, Issue 1
2010
Pages 119-133

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