Toxicity of Beauveria bassiana-28 Mycelial Extracts on Larvae of Culex quinquefasciatus Mosquito (Diptera: Culicidae)

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

Insecticidal potential of <i>Ocimum canum</i> plant extracts against <i>Anopheles stephensi, Aedes aegypti</i> and <i>Culex quinquefasciatus</i> larval and adult mosquitoes (Diptera: Culicidae)

<p>Mosquitoes have developed resistance to various synthetic insecticides, making their control increasingly difficult. Insecticides of botanical origin may serve as suitable natural control. This study evaluates the toxic potential of <i>Ocimum canum</i> (Sims) leaf extract and powder against <i>Anopheles stephensi</i> (Liston)<i>, Aedes aegypti</i> (Lin) and <i>Culex quinquefasciatus</i> (Say) larval and adult mosquitoes. Larval mortality was observed after 24 h recovery period and adult smoke toxicity observed for 40 min duration at 10 min interval. Methanol extract of <i>O. canum</i> showed highest larval mortality against the larvae of <i>C. quinquefasciatus</i> LC₅₀ = 28.3225, LC₉₀ = 44.1150; <i>Ae. aegypti</i> LC₅₀ = 43.327, LC₉₀ = 61.249; and <i>An. stephensi</i> LC₅₀ = 30.2001, LC₉₀ = 48.2866 ppm. The smoke toxicities were 93% mortality in <i>C. quinquefasciatus,</i> 74% in <i>Ae. aegypti</i> and 79% in <i>An. stephensi</i> adults, respectively, whereas 100% mortality was recorded in the commercial mosquito control. Our results suggest that <i>O. canum</i> leaf extract and powder are natural insecticide, and ideal eco friendly approach for mosquito control.</p