Effect Of Biochar Amendment To Soils On Bionomics And Food Utilization Of The Oriental Armyworm Mythimna Seperata(Lepidoptera:Noctuidae)

Biochar amendments to soils have aroused increasing interest in studies,which show their potential for greenhouse gas mitigation,soil improvement and increased crop productivity.A recent study shows a negative effect on a phloem-sucking rice planthopper.However,little attention has been focused on the influence of biochar amendments on herbivorous chewing insects.This thesis study investigated effects of biochar addition on feeding and life history traits the oriental armyworm,Mythimna seperata.Following questions are addressed in this study.(1)How do corn-straw biochar amendments to soils influence immature growth and adult reproduction of M.seperata?(2)Does application of corn-straw biochar affect food consumption and utilization of M.seperata larvae?(3)Does application of wheat-straw biochar influence food consumption and utilization of M.seperata larvae?The study showed that corn-straw biochar may improve M.seperata reproduction,but wheat-straw biochar has negative effects on food consumption and utilization of M.seperata larvae.The main results and conclusions of this study are as follows.1.Effects of corn-straw biochar amendment to soils on immature growth and reproduction of M.seperataTo explore the potential of corn-straw biochar amendments to soils in influencing chewing insect pests,laboratory experiments were conducted using the oriental armyworm Mythimna seperata(Lepidoptera:Noctuidae)as a model.Two types of biochar were tested:corn and wheat straw.Biochar was added at the level of 0,15,30,or 50 g/kg to soils to the pot in which wheat was planted.Neonate larvae were individually transferred onto potted wheat seedlings and observed throughout their development.Larval duration showed a linear downward trend across increasing levels of biochar treatment,from 20.33 d under the control down by 7%to 19.0 d at the highest level of biochar treatment.Pupal weight showed an downward trend across levels of biochar application,from 0.32 g under the control by a decrease of 12.5%to 0.28 g at the highest level.Larval pupation rate(92.08%)and adult eclosion rate(69.89%)did not change across biochar amendment levels.However,lifetime fecundity demonstrated a linear upward trend across levels of application of biochar,from 142 eggs laid per female under the control to 605 eggs at the highest level of biochar treatment,with a substantial increase of 3.3 times.The results suggest that biochar amendment to soils may improve M seperata reproduction.2.Effects of corn-straw biochar amendment to soils on food consumption and utilization of M seperataTo explore the potential of corn-straw biochar amendments to soils in influencing chewing insect pests,laboratory experiments were conducted using the oriental armyworm M.seperata as a model.Biochar was added at the level of 0,15,or 30 g/kg to soils in the pot in which wheat was planted and grown for 8-11 days before fed to M.seperata larvae.The results showed that the amendment of the corn-straw biochar had no significant impact on food consumption and utilization of M.seperata lavae.The study suggests that corn-straw biochar amendment by 30 g/kg or less had no significant impact on M seperata larvae in food utilization.3.Effects of wheat-straw biochar amendment to soils on food consumption and utilization of M.seperataTo explore the potential of wheat-straw biochar amendments to soils in influencing chewing insect pests,laboratory experiments were conducted using the oriental armyworm M.seperata as a model.Biochar was added at the level of 0,15,or 30 g/kg to soils to pot soils in which wheat was planted and grown for 15-18 days before fed to M seperata larvae.The results showed that,food consumption,digestion and weight increase significantly decreased with increasing concentration of biochar.Food consumption showed a linear downward trend across levels of biochar treatment,from 115.48 mg uder the control down by 11.37%to 102.35 mg at the highest level of biochar treatment.In addition,food digestion coefficient showed a linear downward trend across levels of biochar treatment,from 64.98 mg under the control down by 19.16%to 52.53 mg at the highest level of biochar treatment.Weight increase showed a downward trend across levels of biochar application,from 15.23 mg under the control down by 18.45%to 12.42 mg at the highest level.Biochar application affected food utilization indices.Relative growth rate,relative consumption rate and approximate digestibility showed an inward-curved trend,but efficiency of conversion of digested food and efficiency of conversion of ingested food a outward-curved trend,across levels of biochar treatment.The result of the study suggest that amendment of wheat-straw biochar to soils has an inhibition effect on food utilization of M.seperata larvae.