Larvicidal and ovicidal properties of leaf and seed extracts of Delonix elata (L.) Gamble (Family: Fabaceae) against malaria (Anopheles stephensi Liston) and dengue (Aedes aegypti Linn.) (Diptera: Culicidae) vector mosquitoes

Abstract

Mosquito-borne diseases with an economic impact create loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Extracts from plants may be alternative sources of mosquito control agents because they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products and potentially suitable for use to control mosquitoes. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the larvicidal and ovicidal potential of the crude hexane, benzene, chloroform, ethyl acetate, and methanol solvent extracts from the medicinal plant Delonix elata against the medically important mosquito vectors, Anopheles stephensi and Aedes aegypti (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in methanol extract of leaf of D. elata against the larvae of A. stephensi and A. aegypti with the LC(50) and LC(90) values being 93.59 and 111.83, and 163.69 and 202.77 ppm, respectively. Compared to leaf extracts, seeds have low potency against two mosquitoes with the LC(50) and LC(90) values being 115.28 and 139.04, and 225.07 and 273.03 ppm, respectively. The mean percent hatchability of the eggs was observed after 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. All the five solvent extracts showed moderate ovicidal activity; however, the methanol extract showed the highest ovicidal activity. One hundred percent mortality was observed at 300 ppm for leaf methanol extract and 500 ppm for seed methanol extract of D. elata against A. stephensi and A. aegypti, respectively. These results suggest that the leaf and seed extracts have the potential to be used as an ideal ecofriendly approach for the control of mosquitoes. This is the first report on the mosquito larvicidal and ovicidal activities of the reported D. elata plant.

Ovicidal and Larvicidal Activities of Ethanolic Leaf Extracts of Three Botanicals Against the Malaria Vector - Anopheles Gambiae

“…In the test of the ovicidal potential of D. erecta aqueous leaf extracts against the Dengue vector, Aedes aegypti a concentration dependent increase was recorded with an LC50 value of 340.085 PPM [19]. Similar findings have been documented in Boswellia dalzielii leaf extracts [61], ethanolic extract of Artemisia annua [62], leaf acetone, ethyl acetate, and methanolic extracts of Aegle marmelos, Andrographis lineata and Cocculus hirsutus [63], methanolic leaf extract of Cassia fistula [64], leaf extract of Acalypha indica [65] and those of crude hexane, benzene, chloroform, ethyl acetate, and methanol solvent extracts of Delonix elata [60] against Anopheles species. The increase in the phytochemical constituents present in high concentrations of the plant extract played a remarkable role.…”

“…Tritaeniorhynchus [57] and leaf extracts of Acalypha indica [58] at 200PPM. In contrast, zero egg hatchability in the methanol leaf extract of Coccinia indica and Andrographis paniculata was recorded at 150 PPM for C. quinquefasciatus [59], methanol extract of Cassia occidentalis and Euphorbia hirta [59] 100% mortality was attained against C. quinquefasciatus and methanol extract of Delonix elata was recorded at 300PPM against A. stephensi and A. aegypti [60]. The complete ovicidal activity might be as a result of the plant extract being able to block the micropyle region of the egg, thereby preventing the exchange of gases, which eventually killed the embryo in the egg.…”

Pyrethroid-resistance is modulated by miR-92a by targeting CpCPR4 in Culex pipiens pallens

“…Effective methods for the control of mosquitoes, which are the vector for these diseases, are urgently required. Chemical control is efficient and convenient for large-scale application (Marimuthu et al 2012). Pyrethroids, which are associated with low toxicity in humans and rapid eradication of insects, are commonly used to control mosquitoes by application to bed nets and indoor spraying (Nauen 2007; White et al 2014).…”

MiR-278-3p regulates pyrethroid resistance in Culex pipiens pallens

“…Among the diseases, only dengue fever, affects the life of 3.6 billion people (Zellweger et al 2013). Chemical control is a major method to manage the mosquito borne diseases (Marimuthu et al 2012). Pyrethroids are usually used for the impregnation of bed nets and indoor residual spray (White et al 2014).…”