Secondary plant products against Culex pipiens (Linn.), with reference to some changes detected by scanning electron microscope

Abstract

To find environment-friendly and low pest resistance natural mosquitocide, the bio-effects of smokes and oils obtained from leaves of Eucalyptus globulus and Ocimum basilicum against Culex pipiens (Linn.) were investigated. An influence of smokes and oils was tested on the loss ratio of eggs, larvae, pupae, and adult mortality of 1st and 2nd generations of Culex pipiens. Morphological changes of the 2nd generation, including antennae and mouthparts of larvae and adults, were examined by using the scanning electron microscopy (SEM). The smokes of O. basilicum and E. globulus reduced the ratio value of the insect, especially the eggs' number and adults significantly within 2 generations that lasted 82 days. The impact of O. basilicum smokes on the larval molting and mortality rate was 83.15 and 95.05%, respectively, compared to 29.85 and 82.43 % for E. globulus. The lethal effect of O. basilicum smoke on adults had a loss rate of 100% in both generations than 75.86% by E. globulus. Essential oils from O. basilicum and E. globulus showed a severe and rapid killing effect of C. pipiens within 8 days with a loss ratio of 99.47 and 81.38% of larvae from eggs, respectively. Scanning electron microscopy showed that both smokes could cause prominent malformation to the larval antennae, siphon, and adult mouthparts. In conclusion, either E. globulus or O. basilicum smokes in the long term or either of their oils in the short term could be used as natural repellent agents against Culex pipiens.