Comparative Efficacy of Ocimum basilicum and Ocimum gratissimum Essential Oils Against Cyclas puncticollis Infesting Sweet Potatoes in Burkina Faso

Aims: The aim of the present study was to compare the insecticidal effect of the essential oils Ocimum basilicum and Ocimum gratisiimum on the sweet potato weevil Cyclas punticollis.

Study Design: The aim of this approach was to contribute to the management of the sweet potato weevil in Burkina Faso.

Place and Duration of Study: The experiments were carried out at the INERA Entomology laboratory in Bobo-Dioulasso during the cropping season 2022-2023.

Methodology: Five essential oil concentrations (25; 50; 75; 100 and 125 μL/L) were used. Toxicity tests were carried out by fumigation in jars by depositing a charge of essential oil on a 6 cm disc of filter paper. Batches of ten C. puncticollis adults were introduced into the jars containing a fresh, healthy tuberous root of the sweet potato and immediately closed. Each test was repeated five times. The number of dead insects in each batch (treated and untreated jars) was counted every 30 min up to 5 h of exposure and for 4 days (24 h, 48 h ,72 h and 96h) per observation.

Results: The results showed that the different oils had an insecticidal effect on C. puncticollis and that these oils contained chemical substances responsible for the mortality observed. Indeed, mortality rates of 100% were observed after 2 hours of exposure of the weevils with the 125µL/L concentration of O. gratissimum, followed by concentrations of 100µL/L, 75µL/L, 50µL/L after 24 hours and 48 hours with 25µL/L. With O. basilicum essential oil, 100% mortality was observed after 24 hours of weevil exposure with O. basilicum concentrations of 125µL/L and 100µL/L, followed by 98% mortality with concentrations of 75µL/L, 50µL/L and 25µL/L after 96 hours.

Conclusion: These results suggest that the essential oils of Ocimun gratissimun and Ocimun basilicum can be used in the management of C. puncticollis. However, it would be necessary to carry out a concrete application of these oil extracts on large potato stocks in order to confirm or not their efficacy.