Insecticidal Efficacy of Plumeria Species Leaf Extract

Insecticidal Efficacy of Plumeria Species Leaf Extract on Two Economically Important Insects Populations: Mosquito (Anopheles) and Bean Weevils (Callosobruchus Maculatus)

Aguoru, C. U.*,  Offia, K.L. and Olasan, J. O.

JHMR-CODEDepartment of Biological Sciences, University of Agriculture, Makurdi. Nigeria.

Review method: Single-blind; Peer reviewer comments: 1.

Insecticidal efficacy of two Plumeria species (P. rubra and P. obtusa) foliar extracts was tested on mosquito and beans weevil populations. The extent of efficacy was analysed using linear regression model. The aim was to determine if the plant, as a safer biological control method, could possibly solve the problem of increasing populations of these insects implicated in malaria ailment and food shortages respectively. Completely randomized experimental designs were set up with 4 interaction effects. Each treatment had 5 levels of concentration applied on the test organism and replicated 4 times. Number of dead organisms was recorded at a constant time interval. Percentage mortality was computed at 48hrs. Correlation coefficient R and Coefficient of determination R2 were computed. Equations connecting the dependent variable (mortality) and independent variable (extract concentration) were formulated with corresponding t-values at 95% confidence interval.  Residual statistics was also computed. Explanatory power of the extract-mortality model was depicted by analysis of variance. Reliability Statistics of the overall result was tested using the Cronbach’s Alpha. As a result, P. obtusa yielded mosquito mortality rate of 86.2% while P. rubra was 88.75%.  P. obtusa and P. rubra accounted for 90% and 95% weevil mortality respectively.  Correlation coefficients were very high (Plumeria–mosquito =0.970; Plumeria-weevil =0.968) yielding high coefficients of determination R2 (94% and 93.7% respectively). The two linear regression equations thus allows for accurate predictability of the mortality rate of the insects with 95% confidence limit. Mosquito mortality rate= -7.812 + 38.875 x (Extract concentration). Weevil mortality rate=-4.875 + 39.250 x (Extract concentration). The explanatory power of the two models is significantly high (p<0.05). The overall result of the study was 98.9% reliable and consistent (Cronbach’s Alpha= 0.989). Having confirmed the efficacy of the plant on the two insects using an elaborate statistical approach, the crude extract could be refined and exploited for this purpose. This may find applications in public health, pest and disease management, food preservation and crop protection.

Keywords:  Plumeria, foliar extract, efficacy, insecticidal, regression analysis, mosquito, weevils

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