Effects Of Chilo Suppressalis Under Parasitic Wasp Control On Ecological Results And Rice Yield In Double-cropping Rice Fields

Parasitoid is the dominant natural enemy of Chilo suppressalis,which can regulate the growth and development of the suppressor through various parasitic factors,and effectively prevent and control insect pests without polluting the environment and enhancing the tolerance of the suppressor.So,this study investigated effects of different inoculation modes?Chilo suppressalis+Trichogramma chilonis Ishii,and Chilo suppressalis in 2017;Chilo suppressalis+Chelonus murakatae Munakata,and Chilo suppressalis in 2018?on greenhouse gas emissions and rice yield.The main results of this study are shown as follows.?1?Parasitoids and Chilo suppressalis significantly affected withered sheath rate and root morphology of rice.The withered sheath rates of Trichogramma chilonis Ishii,Chelonus murakatae Munakata and Chilo suppressalis treatments were 13.8%-15.9%,13.1%-14.8%,and 20.5%-21.8%,respectively.Compared with the control,root length,root surface area,root volume,root volume,and root bleeding rate of Chilo suppressalis treatment were significantly decreased by 14.62%-46.14%,27.24%-48.80%,30.23%-53.35%,and 34.62%-51.72%,respectively.Compared with the control,the parasitoid treatment also increased root length,root surface area,root volume,root volume,and root bleeding rate by 14.59%-21.16%,8.59%-29.89%,33.33%-40.82%,and 28.57%-33.33%respectively.The Trichogramma chilonis Ishii treatment increased the root length,root surface area,root volume,root volume,and root bleeding rate by14.59%-21.16%,8.59%-29.89%,33.33%-40.82%,28.57%-33.33%,and the Chelonus murakatae Munakata treatment increased these indicators by 40.50%-52.05%,10.85%-35.35%,30.05%-40.82%,and 11.76%-57.14%.?2?Parasitoids and Chilo suppressalis significantly affected soil physical and chemical properties.Compared with the control,the contents of nitrate nitrogen and soluble organic carbon?DOC?in Chilo suppressalis treatment were significantly reduced by 26.42%-28.67%and 24.37%-30.69%,respectively.No significant difference was observed in nitrate nitrogen content between parasitoids and Chilo suppressalis treatments.Compared with Chilo suppressalis treatment,the DOC content of Chelonus murakatae Munakata treatment was significantly increased by 20.53%.Compared with the control,the ammonium nitrogen content of Chilo suppressalis treatment was increased by 36.35%-42.25%.Compared with the treatment of Chilo suppressalis,the treatments of Trichogramma chilonis Ishii and Chelonus murakatae Munakata were decreased by 15.92%-16.13%and 18.56%-20.02%,respectively?3?Parasitoids and Chilo suppressalis significantly affected gene abundance,net nitrification and denitrification potentials,and N₂O emissions.Compared with the control,the Chilo suppressalis treatment decreased the abundances of AOA-amoA and AOB-amoA by 20.00%-24.71%and 25.36%-34.38%,and increased the abundances of nirS,nirK and nosZ by 38.47%-53.85%,24.81%-26.80%and 28.38%.Moreover,Compared with the control,the Chilo suppressalis treatment decreased net nitrification potential by 11.04%-18.94%and denitrification potential by 28.12%-36.85%,and the N₂O emissions by 12.50%-31.88%subsequently.Compared with the treatment of Chilo suppressalis,the parasitoids treatment could improve AOA-amoA,AOB-amoA abundance and reduce nirS,nirK and nosZ abundance.Compared with the Chilo suppressalis treatment,the Trichogramma chilonisIshii treatment increased AOA-amoA A,AOB-amoA by 16.84%,30.38%,reduced nirS,nirK,nosZ abundance by 23.40%,22.40%,20.01%,respectively.The AOA-amoA and AOB-amoA abundances of Chelonus murakatae Munakata treatment were increased by 12.49%and 20.87%respectively,and the abundance of nirK and nirS were decreased by 18.74%and 12.39%respectively.Compared with Chilo suppressalis treatment,the net nitrification potential of Trichogramma chilonisIshii treatment were significantly increased by 14.34%and the denitrification potential were decreased by 15.22%.Compared with Chilo suppressalis treatment,the N₂O emissions were increased by 14.29%-25.97%and 7.21%-15.94%in Trichogramma chilonis Ishii and Chelonus murakatae Munakata treatments respectively.Compared with the control,the N₂O emissions of Trichogramma chilonisIshii treatment were not significantly reduced,and the N₂O emissions of Chelonus murakatae Munakata were reduced by 11.86%-12.09%.?4?Parasitoids and Chilo suppressalis significantly affected CH₄ emissions and related functional microorganism gene abundance.Compared with the control group,the Chilo suppressalis treatment increased the abundance of mcrA by 21.61%,decreased the abundance of pmoA by 25.54%,and CH₄ emissions was decreased by 19.40%-35.07%.Compared with the Chilo suppressalis treatment,there was no significant difference of CH₄ emissions in Trichogramma chilonis Ishii treatment,and the Chelonus murakatae Munakata treatment increased CH₄ emissions by 19.92%-33.02%.Compared with the control,the CH₄ emissions of Trichogramma chilonis Ishii treatment was decreased by 5.56%-9.40%,and the Chelonus murakatae Munakata treatment was decreased by 13.64%-19.17%.?5?Parasitoids and Chilo suppressalis significantly affected rice yield.Compared with the blank control,the Chilo suppressalis reduced rice yield by 18.24%-32.30%.Compared with the Chilo suppressalis treatment,the Trichogramma chilonis Ishii treatment increased rice yield by 6.82%-23.43%,and the Chelonus murakatae Munakata treatment increased rice yield by 5.41%-15.14%.?6?Correlation analysis showed that the withered sheath rates were significantly negatively correlated with root length,root volume,root surface area and root injury flow,while root indexes were significantly positively correlated with nitrate nitrogen,DOC,MBC,MBN,net nitrification potential,AOA-amoA,AOB-amoA,pmoA gene abundances,and significantly negatively correlated with ammonium nitrogen,denitrification potential,nirS,nirK,nosZ,mcrA gene abundances.Combined with the structural equation model,our study showed that the Chilo suppressalis damaged rice,caused withered sheath,damaged aeration tissue and root growth,affected gas exchange,nutrient transport,soil physical and chemical properties,nitrification,denitrification and related microorganisms,regulated greenhouse gas emissions.In addition,Chilo suppressalis can cause bug to injure a plant,cause empty and dented grain to increase and reduce production.As mentioned above,parasitoids can effectively control Chilo suppressalis,and thus increase rice yield and mitigate greenhouse gases compared with the healthy rice fields.So,our results suggest that this measure is an efficient,ecological and biological control method.