Comparative Assessment Of The Fumigant Action Of Volatile Oils From Three Garlic Cultivars On Faba Bean Beetle Bruchidius Incarnatus (boh.)

Abstract

This study was carried out under laboratory conditions at the Faculty of Agriculture, University of Khartoum, Shambat, Sudan, to evaluate insecticidal activity, oviposition inhibitory and ovicidal effect of garlic volatile oils from Chinese, Egyptian and Sudanese cultivars against faba bean beetle Bruchidius incarnatus (Boh.). The fumigants were tested at concentrations of 0.01%, 0.1%, 1%, 5% and 10% for insecticidal activity and oviposition inhibition. The corresponding concentrations for the ovicidal activities were 0.01%, 0.05%, 0.1%, 1%, 2%, 10% and 20%. The exposure periods were 24, 48, 72, 96, 120, 144 and 168 hours. Volatile oils from Chinese and Sudanese garlic were extracted by steam distillation and ethanol, respectively, while a ready-made Egyptian garlic oil was obtained form from El-Captain Company (Egypt). The results indicated that the volatile oils of garlic were effective against the test insects and caused significant mortality compared to the control. The results generally showed that the Chinese garlic oil was more effective and gave 100% mortality of males and females of the test insects after 24 hours of exposure followed by the Egyptian and Sudanese garlic oils. The Effects were dose and exposure period related. The mortality caused by the three oils followed the order; Chinese> Egyptian> Sudanese garlic oils. The respective male median lethal doses (LD50 %) after 72 hours of exposure were 0.03, 0.006 and 3.77 for Chinese, Egyptian and Sudanese oil, respectively, while they were 0.06, 0.03 and 3.77 for female: The respective male median lethal times (LT50 hrs) at concentration 0.01% were 55.88, 48.62 and 79.93 for Chinese, Egyptian and Sudanese oil, while they were 57.57, 57.76 and 84.99 for the female, respectively. The results of oviposition inhibitory assay showed a considerable reduction in number of eggs laid, and significantly different from the control sets. The effectiveness of the volatile oils was related to dose and exposure period. The oviposition inhibiting effects followed the order; Chinese> Egyptian> Sudanese oil. The results of ovicidal assay indicated that garlic volatile oils caused significant mortality against the eggs of the test insect and effects were significantly different from the control sets. The ovicidal effects followed the order; Chinese> Egyptian> Sudanese oil. The respective median lethal doses ((LD50 %) were 0.025, 0.034 and 0.21%. The results of the study revealed that garlic volatile oils of the three cultivars have insecticidal, oviposition inhibitory and ovicidal activities against the test insect, and the responses were dose and exposure period related. The efficacy of the three types of garlic oils followed the order; Chinese> Egyptian> Sudanese oil.