Effects Of Biochar Amendment To Soils On Life History Traits And Food Utilization Of The Rice Leaf Folder Cnaphalocrocis Medinalis (Lepidoptera:Pyralidae)

Biochar has been found to improve soil physical and chemical properties,reduce carbon and nitrogen emissions,absorb heavy meatal irons and increase crop productions.A growing attention has been focued on biochar effect on herbivorous insects.Previous studies have exbhited that biochar amendment to soils impairs developmental and reproductive performances of phloem-sucking planhoppers on rice and aphids on wheat.The only study on chewing herbivors showed that biochar did not have strong effect on folivorous caterpillar Mythimna separate on wheat.More studies on chewing insects are needed.This thesis study focued on the rice leaf folder Cnaphalocrocis medinalis to address the following questions by laboratory and field experiments:(1)How does biochar amendment to soil affect the life history traits of C.medinalis?(2)How does biochar amendment to soil affect the feeding and food utilization of C.medinalis?(3)How does biochar amendment to soil affect the population of C.medinalis in paddy field?1.Effects of biochar amendment to soil on life history traits.Four biochar amendment rates were applied to soil:0(CK),1.5%(WB15),3.0%(WB30)and 5.0%(WB50)for growing rice plants.Plant leaves were excised to feed of C.medinalis larvae,whose developmental and reproductive performances were recorded.Biochar amendments significantly prolonged larval development period and redeuced fresh body weight of both male and female pupae.The pupal body weight under WB30 was 23.1%(male)and 22.8%(female)less than CK.Adult longevity of was significantly shortened by biochar amendments.With female adults being reduced by 36.3%under WB30 and 27.9%under WB50 compared to CK.Biochar amendments did not influence fecundity.The results from the current study suggest that biochar amendment to soil has a negative effect on larval development and adult longevity,yet does not have an effect on reproductive potential.2.Effects of biochar amendment to soil on feeding and food utilization.Four biochar amendment rates(0,1.5%,3.0%and 5.0%)were applied to soil for growing rice seedlings.Leaves were excised to feed C.medinalis 5th instar larvae.Food utilization coefficients were estimated.Biochar amendments significantly afect food consumption with a decrease by 40.30%under WB30 and 16.63%under WB50 compared to CK,but an increase by 14.66%under WB15.Biochar amendments reduced the food digestion by 27.61%under WB30 and 16.26%under WB50 compared to CK,but increased it by 15.39%under WB15.Biochar amendments did not affect body weight gain.But the classical food utilization index has significant differences.Specifically,biochar amendments increased the food conversion,digestion and approxiamate digestibility and reduce the efficiency of conversion of digested food and the efficiency of conversion of ingested food under WB15 compared to CK,while WB30 and WB50 is contrary to WB15.Biochar amendments increased the relative consumption rate and the relative growth rate compared to CK.The results suggested that WB30 and WB50 has negative effects on feeding and food utilization of C.medinalis larvae.3.Effects of biochar amendment to soil on population of C.medinalis in field.Complete random plot design and split-plot design were applied in paddy fields at Changshu and Luhe sites.Biochar was applied at rate 20 t·hm-2.Sampling of adults was made by visually counting flying moths when disturbing rice plants.The results showed that biochar amendments significantly affected population size at Changshu site and did not at Luhe site.