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

Waheed Ahmed Abdelhanid Sayed,Helmy El-Bendary,Alexandra El-Helaly

doi:10.1186/s41938-019-0201-1

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.

Highlights

Baculoviruses are one of the most environmental safe bio-pesticides for lepidopteran pests
Impact of tested oils on UV protection Inactivation of SpliMNPV was shown at 30-min exposure time either alone or combined with tea tree and marjoram oils, where the mortality percentages were significantly decreased as the UV exposure times increased
The data of original activity remaining (% OAR) in Table 1 demonstrated that the combination of SpliMNPV with orange oil was higher % OAR (73.67%) than in the combinations with tea tree oil, marjoram oil, and SpliMNPV alone (11.93, 1.16, and 0.0% OAR, respectively) at 120-min UV exposure time

Summary

Background

Baculoviruses are one of the most environmental safe bio-pesticides for lepidopteran pests. The cotton leaf worm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) multiple nucleopolyhedrosis virus (SpliMNPV) is one of the Baculovirus groups that is specific for S. littoralis and can be used effectively in its management. It is severely affected by the UV radiation of sunlight, which leads to pyrimidine dimer formation in the viral DNA chains and reduces the SpliMNPV persistence in the field (Jones et al 1993 and Yoon et al 2000). The present trial aimed to evaluate the use of three commercial plant oils, orange, tea tree, and marjoram, as adjuvants to SpliNPV activity for lepidopteran pest control

Materials and methods

Results and discussion

Conclusions