Increasing the efficacy of the cotton leaf worm Spodoptera littoralis nucleopolyhedrosis virus using certain essential oils

Abstract

Baculoviruses inactivation by UV sunlight is considered one of the most important factors that reduce their potential use in insect management programs. The three antioxidant essential oils, marjoram, orange, and tea tree were tested as protective additives to the multiple nucleopolyhedrosis virus (SpliMNPV) against UV. The results revealed that the orange oil was promising for virus protection, while the tea tree oil and marjoram oil did not protect the virus. The results also showed that the pathogenicity of the combination treatment of SpliMNPV and orange oil was increased drastically by adding the LC50 (1.0%) concentration of the oil to the virus concentrations. Consequently, the LC50 of the mixture was reduced to 5.3 × 103 PIB/ml compared to 3.2 × 105 PIB/ml concentration of virus alone. Concomitantly, the ovicidal and larvicidal effects of orange oils were determined. The results suggested that the combination treatment of orange oil and SpliMNPV could be used as an effective method for the cotton leaf worm, Spodoptera littoralis (Boisd.), management.