Effect Of Agricultural Landscape Structure On Biological Control Of Parasitoids For Chilo Suppressalis

The rice stem borer Chilo suppressalis is one of the most serious pests of rice in China,the parasitoids,as the important natural enemy,can effectively regulate the population of C.suppressalis in rice fields.In this paper,based on the context of the C.suppressalis and diversity of agricultural landscape in Jiangxi Province,evaluating the population dynamics and collection methods of egg parasitoids of C.suppressalis in rice field,analyzing the parasitism rate and dominant parasitoids of overwintering larvae in C.suppressalis from different counties of Jiangxi province and effect of agricultural landscape pattern on control function of parasitoids on overwintering larvae of C.suppressalis.1 The population dynamics and collection methods of egg parasitoids on Chilo suppressalis in the rice fieldThe population dynamics and collection methods of egg parasitoids of C.suppressalis were studied during May to October in rice fields,results show egg parasitoids of C.suppressalis were first founded in late June,and had two peaks in middle July and in late August with the highest egg parasitism rate 66.7% and 24.1%,respectively.The numbers of egg parasitoids during middle rice period was more than during early and late rice period.Comparison with the alive rice,fresh rice leave and artificial egg card used to collect egg parasitoids,show the method of alive rice was best.2 The parasitism rate and dominant parasitoids of overwintering larvae in C.suppressalis from different counties of Jiangxi provinceThe depressing effect on the overwintering population is essential in integrated pest management,but little is known about biological mortality factors that regulate C.suppressalis populations during the entire overwintering processes.Here,we test the bio-control effect of larval parasitoids on overwintering larvae,assume that key parasitoids strengthen the over-wintering population depressing.The natural parasitism incidence and related dominant parasitoids on overwintering larvae were investigated in two successive winters in 2015 and 2016.Parasitism rate were also assessed in larvae that collected from fifteen different counties in 2016.The results showed that parasitism incidence and the dominant parasitoids on overwintering C.suppressalis larvae were significantly different in different sampling date and sites.Overwintering larvae of C.suppressalis were mainly parasitized by Cotesia chilonis,and fewer individuals were parasitized by Eriborus sinicus and Microgaster russata.Regression analysis indicated that the natural parasitic incidences on overwintering C.suppressalis larvae were positively influenced by the over-wintering larval population density.The current work provides support for the pests overwintering population control hypothesis by showing that bio-mortality factors that regulate C.suppressalis population during the entire winter and the effectiveness of parasitoid communities.3 Effect of agricultural landscape pattern on control function of parasitoids on overwintering larvae of C.suppressalisThis study focus on the ecological service function of agricultural landscape diversity in rice planting area,and assessing the effect of agricultural landscape pattern on control function of parasitoids on overwintering larvae of C.suppressalis.Survey show the parasitism rates of overwintering larvae of C.suppressalis rang from 1.6% to 44.4% in 2017 and 1.1% to 52.3% in 2018,respectively.Five species of parasitoids were founded,among them the dominant species were C.chilonis and E.sinicus,with the highest rates of 50% and 15%,respectively.Total parasitism rate was negatively related to the proportion of non-crop habitats and positively related to the proportion of crop land,however,the relationship between the parasitism rates of two parasitoids on C.suppressalis and non-crop habitats was completely opposite,the parasitism rates of C.chilonis on C.suppressalis was negatively related to the proportion of non-crop habitats,but the parasitism rates of E.sinicus on C.suppressalis was positively related to the proportion of non-crop habitats.