Insecticidal properties of tea seed saponin against the mulberry snout moth, Glyphodes pyloalis Walker (Lepidoptera: Crambidae)

The mulberry snout moth, Glyphodes pyloalis Walker, is an important and destructive pest of mulberry in Asia. Because of its extensive damages on mulberry leaves and making obstacle in sericulture, it is inevitable application of synthetic and biorational insecticides. Excessive application of insecticides may lead to develop resistance and to pollute environment mainly water resources therefore use of natural products (like botanical insecticides) is of great importance as an alternative. In the present study, a saponin was extracted from tea seeds and treated against G. pyloalis larvae. Results showed that a concentration of 2.8 % saponin caused 50 % mortality in treated larvae compared to the control, and the LT₅₀ (Median Lethal Time) was 6.34 days. Also, the repellency index increased in a dose-dependent manner. Tea saponin treatment increased the duration of egg hatching, larval and pre-pupae periods compared to the control. Activities of digestive carbohydrates and proteases were significantly reduced in the exposed larvae. Additionally, saponin treatment significantly decreased the activity of digestive enzymes but it statistically induced antioxidant system in G. pyloalis larvae. The obtained results suggested that tea saponin can affect important biological and physiological processes of G. pyloalis and it may be used as an efficient biopesticide in control of G. pyloalis population.