Effects Of Biochar Amendment To Soils On Feeding Behavior And Abundences Of The English Grain Aphid Sitobion Avenae

Biochar amendments to soils have attracted growing attention recently owing to the potential in greenhouse gas mitigation,soil improvement and increasing crop productivity.However,less attention has been focused on the influence of biochar amendments on herbivorous insect pests.The English grain aphid,Sitobion avenae(Fabricius)is among the most important pests on wheat crop.Plot trial were carried in paddy fields to examine the effect of biochar amendments on abundances of S.avenae in the field.To investigate the potential of biochar amendments in affecting S.avenae feeding behavior,laboratory experiments were carried out to evaluate effects of biochar type(made out of corn,wheat or rice)by amount added to soils(three levels:0,30,and 50 g/kg)on feeding behaviors of aphids on wheat leaves.Electrical penetration graph(EPG)technique was used to measure feeding performances of eight waveforms,named as Np(non-penetration),C,G,pd,Gspot,F,El,and E2.These waveforms describe stylet penetration activities,with NP for no stylet penetration,C for reaching to the epidermis and mesophyll without salivation and ingestion,G for actively ingesting xylem sap,pd for piercing cell membrane,Gspot for ingesting actively before salivating and ingesting,F for encountering resistance,E1 for starting ingestion of phloem sap,and E2 for passively ingesting phloem sap.These electrical waves were individually measured by frequency,duration and latency to start.The main results and conclusions from the bioassay are summarized as follows.1.Influence of biochar treatments on frequency of electrical waveformsThe bioassay showed that the 30 g/kg and 50 g/kg biochar treatments had a significant effect on the number of stylet probing,pd,Gspot,and E1 waves.The stylet probing in number increased by 49.7%and 69.5%the pd wave increased in frequency by 29.4%and 59.5%,the Gspot wave in frequency increased by 86.9%and 64.2%,under the 30 g/kg and 50 g/kg treatments compared to the controls.The E1 wave was influenced in frequency by the interaction between application level and kind of biochar used,increasing by 53.9%under the 50g/kg biochar treatment compared to that under the 30g/kg treatment,yet decreasing by 35.5%under the 50g/kg treatment compared to that under the 30g/kg biochar treatment.The results suggest that biochar amendments increase the difficulty of feeding on wheat leaf by S.avenae.2.Influence of biochar treatments on the duration of electrical waveformsThe bioassay showed that the 30 g/kg and 50 g/kg biochar amendments had a significant effect on the duration of stylet probing,Np,E2,and C waves.The duration of Np wave increased by 73.0%and 91.3%,and of C wave by 24.1%under the 50g/kg treatment in comparison to the control.The duration of E2 wave decreased by 28.1%and 30.8%under the 30 g/kg and 50 g/kg treatments in comparison to the control.These results suggest that biochar application can increase the time for non-penetration and stylet penetration reaching to the target cell to ingest phloem.3.Influence of biochar treatments on the occurrence of respective electrical waveformsThe bioassay showed that biochar amendments had no effect on the occurrence of all electrical waveforms.The results suggest that biochar amendments had no effect on the occurrence probability of each waveforms.4.Effects of biochar amendment on abundances of S.avenae in the fieldThe abundance of the English grain aphid decreased by 16.8%in the biochar amended wheat field compared to that in control field.The result suggests that biochar amendments to wheat field had a negative effect on S.avenae population growth.