Abstract
Microbial-based pest control is an attractive alternative to chemical insecticides. The present study sought to evaluate the toxicity of the entomopathogenic fungus Beauveria bassiana-28 ethyl acetate extracts on different larval stages and pupae of Culex quinquefasciatus mosquitoes. B. bassiana-28 ethyl acetate mycelial extracts produced mosquitocidal activity against larvae and pupae which was comparable to that of the commercial insecticide B. bassiana-22 extract. The LC50 (lethal concentration that kills 50% of the exposed larvae) values of B. bassiana-28 extracts for 1st to 4th instar larvae and pupae were 11.538, 6.953, 5.841, 3.581 and 9.041 mg/L respectively. Our results show that B. bassiana-28 ethyl acetate mycelial extract has strong insecticidal activity against larval and pupal stages of Cx. quinquefasciatus. Fourier transform infrared spectrum study of B. bassiana-28 extract shows peaks at 3226.91; 2927.94; 1593.13; 1404.18; 1224.18; 1247.94; 1078.21; 1018.41; 229.69; and 871.82 cm−1. Major spectral peaks were observed at 3226.91 cm−1, assigned to N–H stretching, 2927.94 cm−1 assigned to C–H bonding and 1595.13 cm−1 assigned to C–O stretching. Gas Chromatography-Mass Spectrometry studies of B. bassiana-28 ethyl acetate crude extract showed presence of six major compounds viz. N-hexadecanoic acids (13.6040%); Z,Z-9,12 octadecadienic acid (33.74%); 9-eicosyne (10.832%); heptacosane (5.148%); tetrateracontane (5.801%); and 7 hexyleicosane (5.723%). Histology of mosquito midgut tissue shows tissue lysis as a result of B.bassiana-28 extract exposure. The study shows that bioactive molecules obtained from B. bassiana-28 mycelial extract has insecticidal properties and can be used as alternative for mosquito control.
Highlights
Mosquitoes are responsible for several vector-borne diseases [1]
Female Culex quinquefasciatus mosquitoes are responsible for lymphatic filariasis in tropical and subtropical regions [3,4,5,6]
Based on LC50 and LC90 values it was found that B. bassiana-28 mycelium extract had insecticidal activity similar to that of the commercial microbial insecticide B. bassiana-22 on 1st to 4th instar of Cx
Summary
Mosquitoes are responsible for several vector-borne diseases [1]. Mosquitoes are classified into three subfamilies: Anophelinae, Culicinae and Toxorhynchitinae [2]. Many researchers have reported that mosquitoes show resistance to synthetic chemical insecticides [7,8,9] In this scenario, bioactive compounds of biological origin from bacteria, fungus, plants and entomopathogenic microbes are being bio-prospected as alternatives to chemical insecticides [10,11,12,13,14]. Havehave been been evaluated for their insecticidal potential and houseflies houseflies[24] Entomopathogenic evaluated for their insecticidal potentialon onmosquitoes mosquitoes and fungus, . Can as pests [25,26] These EPF Beauveria spp., are highly specific to mosquitoes [27] and can be developed be developed as potential insecticides for the control of mosquito larvae. Performed larval at different time durations (6, 12 and 24 h post-treatment)
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