Evaluation of Origanum majorana L. (Lamiaceae) essential oil and its encapsulation in nanoformulation system on mortality and repellency against Tetranychus urticae Koch (Αcari: Tetranychidae)

Abstract: Tetranychus urticae Koch (Acari: Tetranychidae) is a serious pest of many crops.
Development of alternative means for its control such as miticides based on essential oils (EOs) of aromatic plants hold promise. Our study focused on the assessment of the EO of Origanum majorana L. in the control of T. urticae with emphasis on possible enhancement and extension of its activity after its encapsulation in biodegradable and biocompatible carriers (yeast cells and β-cyclodextrin). Mortality of T. urticae larvae or adults was recorded daily for 7 days after the application of 1 ‰ (v/v) EO emulsion or encapsulated oil. In a repellency bioassay, the number of females presented on each side of a bean leaf disc half-dipped in the emulsion or encapsulated oils was recorded 1 h, 2 h, 4 h and 24 h after treatment. Terpinen-4-ol, γ-Terpinene and α-Terpinene were the main components of the EO. Mortality of nymphs was 84 % and kept at similar levels after the application of the encapsulated oils whereas mortality of adults was 60 % that increased to 88 % but decreased to 48 % in the case of β-cyclodextrin and yeast cells, respectively. The encapsulated oils showed a much longer period of bio-activity than the emulsion (4 to 5 days in comparison to 1-2 days for the emulsion). The EO was highly repellent and similar results were recorded for both encapsulated EOs. Therefore, the EO of O. majorana can be effective in the control of T. urticae and its encapsulation in β- cyclodextrin significantly increases its efficacy and persistence.