E.N. NWANKWO , R.I. EGWUATU, N.J. OKONKWO AND N.A. OZUMBA, S.C. EWUIM , K.K. OKOLO AND C.E. AKUNNE
Abstract
Toxicity of Novaluron (Mosquiron 100EC), a new chitin synthesis inhibitor type of insect growth regulator and Annona muricata Seed Oil (AMSO), was evaluated in the laboratory against larvae of the Aedes aegypti (Diptera: Culicidae) at six concentrations of the technical materials ranging from 6.25 - 200µg/mL; including control. The bioassays were carried out in the laboratory at temperature of 27±2oC and 82±5% relative humidity. Four replicates of each concentration of the respective toxicants in a Completely Randomised Design (CRD) were challenged with 20 active larvae of a given instar. Mortality resulting from eclosion inhibition was monitored at 3-hourly intervals for a period of 3, 6, 9, 12 and 24 hours post-treatment. Data were analysed using log-probit regression and analysis of variance. Results showed that dosage-related mortality responses were noted at the different time interval, and these were significant (P< 0.05) for both instars. Results indicated 90 and 95% mortality of 2nd and 4th instar larvae of Ae. aegypti respectively at the highest concentration (200µg/mL) of Novaluron while sublethal dosage (6.25µg/mL) resulted in 50% and 45% mortality of 2nd and 4th instars respectively. Exposure to Annona muricata seed Oil resulted in 100% mortality of both 2nd and 4th instars at highest concentration and 35% and 40% mortality, respectively on the 2nd and 4th instars at sublethal dosage. Both toxicants showed significant inhibition of emergence following post-treatment culturing. LD50 values for 2nd instars larvae were 2.5061µg/mL and 23.9880µg/mL of Novaluron and A. muricata oil, respectively. The study suggests that Annona muricata seed oil has shown promise as biopesticide for Ae. aegypti larvae control.