Biocidal potential of clove oils against Aedes albopictus – A comparative study

Abstract

The first phase of the study involved evaluation of leaf and bud oils of clove, Syzygium aromaticum for their biocidal (i.e. ovicidal and larvicidal) activity against Aedes albopictus. Eggs and fourth instar larvae were exposed to different concentrations of the oils to investigate their comparative efficacy against the target mosquito species. In the second phase of the study, biocidal activity of ‘test formulation’ derived from the leaf oil and commercial mosquitocide, Prallethrin were estimated by the
same method to compare the efficacy of the former with popular mosquitocides. Mortality data were analyzed by a computerized Log-Probit analysis (StatsDirect). Ovicidal assay of the oil samples recorded EC50 values of 0.37 and 2.0 mg/ml respectively for leaf and bud oil. Larvicidal assay showed LC50 and LC95 values of leaf oil as 5.3 and 7.03 mg/ml respectively, while bud oil recorded LC50 and LC95 values of 17.84 and 23.99 mg/ml, respectively. The ‘test formulation’ recorded EC50 value of 1.63 mg/ml, LC50 of 3.67 mg/ml and LC95 of 13.49 mg/ml respectively, indicating levels comparable to that of prallethrin. Third phase of the study involved chemical characterization of the oil samples using GC-MS.
Eugenol constituted the major component of both the oils. The study demonstrated the potential of clove oil as a biocide against A. albopictus and warrants further standardization of the ‘test formulation’