Abstract
The aim of this study was to evaluate the topical toxicity of the Esenbeckia pumila plant extracts on workers of the Atta laevigata and Acromyrmex balzani. Five leaf fractions E. pumila were drawn viz., the hexane, ethanolic, dichloromethane, ethyl acetate and methanolic extracts, as well as the ethanolic fruit extracts. Further, the phytochemical leaf extract exploration was performed, and the secondary compounds detected were as follows: flavonoids, anthraquinones, coumarins, cardioactive heterosides and tannins. The different leaf and fruit extract fractions were first diluted in 70% ethyl alcohol, and different doses were topically applied to the A. laevigata and A. balzani workers. All the fractions extracted exhibited formicidal effects and this effect was greater to A. laevigata rather than to A. balzani. Only a small percentage of the workers succumbed within the first few hours of application of the different extracts in comparison with the workers which died only after a longer exposure time (72 h) implying a delayed effect of E. pumila extracts.
Highlights
In the catalog, Grainge and Ahmed (1988) recorded that about 2,400 plant species could have insecticidal properties
The acute toxicity of all the E. pumila leaf extract fractions tested on the A. laevigata workers was confirmed 24 hours after topical application, i.e. the worker mortality increase at increasing concentrations of leaf fractions (Table 1)
Lower LD50 was noted after 72 hours of the application, implying that the extract of the fraction EPFEA (LD50 = 95.34), was more toxic to the A. balzani workers showing a value that was very close to that of the EPFrE fraction (LD50 = 96.89)
Summary
Grainge and Ahmed (1988) recorded that about 2,400 plant species could have insecticidal properties. According to Aguiar-Menezes (2005), the plant families possessing such properties include Meliaceae, Rutaceae, Asteraceae, Annonaceae, Labiatae and Canellaceae. Plant ingredients may exhibit toxic or undersirable effects on no-target organisms, including humans. Mostly plant insecticides are inherently less harmful than conventional pesticides (Upadhyay, 2012). They usually affect only the target and closely related organims, in contrast to broad spectrum, conventional insecticides that may affect organisms as different from insects as bird and mammals (Solecki, 2004). The plant insecticides induce inhibition of food, decreased motility, interference in the intestinal synthesis of ecdysonium, inhibition of the chitin biosynthesis, strain pupae and adults, minimized fecundity and longevity, sterilization, inhibition of oviposition and mortality of both the immature and adult stages (Baskar, Maheswaran, Kingsley, & Ignacimuthu, 2011; Vendan, Baskar, Paulraj, & Ignacimuthu, 2016)
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