Vol. 10, Issue 3, Part A (2023)

Author(s): Ismail Muhammad, Muinat Abdullahi Muhammad, Rejoice Asher and Abdulmalik Bala Shuaibu

Abstract: Biological control serves as the most effective and environmentally friendly strategy for control several mosquito specie. Different biological control agents in different forms and formulations are widely used. Therefore the aim of this research was to assess the larvicidal activity of the lower doses of commercially synthetic Bacillus thuringiensis israelensis (Vectobac WDG) against the third instar larva of Culex mosquito. One hundred and fifty blood-fed female anopheles mosquitoes were collected from different resting sites using an aspirator and allowed to breed until the first instar larva appeared. The larvae were monitored and fed with 10% yeast until the third instar emerged. 240 healthy third instar larvae were selected and grouped into three treatments containing sixty (60) larvae each and replicated three times. The first, second and third treatments were respectively treated with 2.5, 1.25 and 0.833g of Vectobac WDG. Each treatment has a control containing twenty (20) larvae each. Larval mortality was determined using glass rod at an interval of 15 minutes for a period of 24 hours. ANOVA was used to statistically analysed differences in the larval mortality between the treatment and probit analysis was used to determine the lethal concentration (LC) and the lethal time (LT). Mortality of 1(6.7%) was observed in the first treatment (2.5g) after 15 and 30 minute of exposure. The highest mortality of 60(100%) was observed in all the treatments after 24 hours of exposure, except in the first treatment where 59(98.33%) was observed. Statistically, there was no significant difference (F=11.031, P> 0.05). 20.87, 120.57 and 201.84g were determined to be LC50, LC90 and LC99 respectively and LT50, LT90 and LT99 were found to be, while 622.93, 1847.33, and 2845.53minute respectively. In conclusion Vectobac WDG has demonstrated a high level of efficacy as it revealed 100% larval mortality even at a lower recommended dose. Further research should be carried out to study the impact of other biological and environmental factors on the efficacy of Vectobac WDG.

DOI: 10.22271/23487941.2023.v10.i3a.673