Bamboo charcoal by-products as sources of new insecticide and acaricide

Abstract Bamboo tar, a dark-brown residue of the precipitated part obtained by setting the crude bamboo vinegar for 6 months or by distilling the crude bamboo vinegar under a reduced pressure, was collected from ten bamboo charcoal factories in China. All samples were analyzed by GC–MS for various concentration of phenolic derivatives (the concentration varying from 13.93% to 61.8%) and the highest total phenolics concentration was selected as a highlighting sample, manufacturing the two pesticidal formulations of bamboo tar emulsifiable concentrate (BTEC) and bamboo tar aqueous solution (BTAS). Greenhouse and field tests were conducted to examine the mortality of BTEC and BTAS against the soybean aphid, the citrus red mite, tea spider mites and tea leafhopper. The greenhouse test showed the activity against three pests was: Tetrenychus cinnabarinus  >  Empoasca flavescens  >  Aphis medicaginis . A bioassay showed strong contact toxicity with LC 50 and LC 90 values of 5.84–12.53 g/L of BTEC and 11.66–22.56 g/L (the actual bamboo tar) against three pests, respectively. Field test showed the corrected mortality was not significantly different between the treatment 2 g/L BTEC and the control 0.05 g/L 10% imidacloprid WP, 20% dicofol EC 0.25 g/L, 25% propargite EC 0.032 g/L against the four pests. In addition, 50% BTEC animal (involve in rats, rabbits, or guinea pigs) safety tested showed the acute oral toxicity LD 50 was 4.64 g/kg for males and 3.69 g/kg for females. The acute dermal toxicity is LD 50 >2 g/kg in males and females and it belongs to grade I weak sensitizing matter. Therefore, bamboo tar is a promising material, which might be used as a new natural insecticide and acaricide in the agricultural field to reduce t he dependence on synthetic pesticides.