Biological activity of tannins extracts from processed Camellia sinensis (black and green tea), Vicia faba and Urtica dioica and Allium cepa essential oil on three economic insects
Ahmed F. El-Aswad, Justus Aisu, M. H. Khalifa
Abstract
Abstract Nowadays to move toward a more sustainable agriculture, use of pesticide alternatives that have positive effects and play critical roles toward reducing the use of pesticides should be used. Laboratory bioassays were carried out to analyze the bioactivity of tannins isolated from urtica weed leaves (U), bean hull (B), black tea (BT) and green tea (GT) against larvae of cotton leafworm Spodoptera littoralis (Boisduval) using food mixing technique and essential oil isolated from onion against larvae of cotton leafworm, adults of rice weevil and houseflies using fumigation technique. The results showed that during the first week of treatment, tannins extracted from U had the strongest antifeedant activity with an EC 50 of 33.034 μg/g followed by tannins extracted from B (EC 50 = 47.839 μg/g). In the second and third week, tannins isolated from B depicted highest antifeedant activity (EC 50 = 37.733 and 84.828, respectively). Furthermore, the isolated tannins induced notable larval growth inhibition on S littoralis . On the other hand, mortality percentage of onion essential oil on tested insects clearly increased with both increased concentration and exposure time. The LC 50 (μg/cm 3 ) at 30 min reflected that the essential oil had a greater toxicity to cotton leafworm with a LC 50 = 2.15 μg/cm 3 while least toxic to house flies (LC 50 = 16.09). The repellency action based on LT 50 values was seen to be highly effective in houseflies (LT 50 = 1.85 min). The results demonstrated that tannins and essential oil could be applicable in the management of insect pests to decrease ecologically detrimental effects of synthetic insecticides.