Effects of five plant essential oils on the protein content and digestive enzymes of Ephestia kuehniella.

The Mediterranean flour moth or mill moth Ephestia kuehniella is a common pest of cereal grains, especially flour. In this research, the sublethal effects of essential oils isolated from five medicinal plants including Allium sativum, Glycyrrhiza glabra, Rosmarinus officinalis, Salvia officinalis, and Piper nigrum were investigated on the protein content and digestive enzymes activity of the fifth instar larvae, under laboratory conditions. The GC-MS analysis of the essential oils showed that tetracosamethyl cyclododeca siloxan, aristolene, α-pinene, β-thujone, and caryophyllene were the dominant constituents for each essential oil, respectively. The enzymatic activity was investigated by the treatment using the LC30 concentration against the larvae that were 2.86, 12.03, 2.19, 7.84, and 9.39 µl/l air, respectively. Results revealed that there were significant differences among the treatments on total protein content and enzymatic activities (F5,12 = 2.95, 3.56, and 7.07). About the total protein content, the control and treatment with R. officinalis essential oil showed the highest and lowest concentrations (1.0288 ± 0.0212 mg/ml versus 0.7333 ± 0.0329 mg/ml). The highest amylolytic activity was also seen in the control (0.0551 ± 0.0025 mU/mg) and the lowest being in R. officinalis oil treatment (0.0373 ± 0.0009 mU/mg). Moreover, the highest and lowest proteolytic activities were observed in the control (5.5063 ± 0.1086 U/mg) and R. officinalis essential oil (3.3028 ± 0.1077 U/mg). Accordingly, R. officinalis essential oil could be applied for the control of E. kuehniella.