Geostatistics and GIS analysis of spatial patterns of Myzus persicae and Hylyphantes graminicola in peach orchards under chemical pesticide stress

The overuse of chemical pesticides not only kills insect pests and natural enemies, but also affects the spatial relationship between insect pests and their natural enemies. Hylyphantes graminicola is a key predator of Myzus persicae in peach orchard eosystems. In this paper, we systematically investigated M. persicae and its predator H. graminicola populations in peach orchards under chemical pesticide stress at different times (from mid April to early September), used geostatistics and geographic information system (GIS) to analyze the spatial structure, and used ordinary Kriging interpretation with Gaussian, Exponential, Spherical and Circular models to simulate the spatial distribution of the two species.The aim of the study was to understand the spacial distribution of M. persicae and its predator H. graminicola under long-term applicaiton of chemical pestcides and provide the theoretical support for ecological control of peach garden pests. The results suggested that both H. graminicola and M. persicae had random spatial arrangement within 10 iterative times of investigations. The proportions of spatical sturcture C0/(C+ C0) of populations of H. graminicola and M. persicae were 0.788 80.983 9 and 0.811 60.980 6 indicating weak spacial relathship bewteen two populaitons under long-term chemical pestcide stress. The nugget values and partial sills of H. Graminicola, M. persicae were respectivel 0.254 2 4.896 3, 0.218 40.749 9 and 0.010 50.250 0, 0.004 80.075 7, respectively, indicating random spatial arrangement, too. The correlation of spatial distribution distance of two species was relatively weak, the distance ranges for the two species was 6.863 0 43.174 1 m. Though the model parameters of semivariograms for M. persicae and H. graminicola at different times were changed greatly due to population density, temperature, and peach growth, the spatial patterns of the two populations were random under long-term chemical pesticide stress. Our study demonstrated that under long-term and excessive use of chemical pesticides in peach orchards, the proportions of H. graminicola and M. persicae spatial structure was greater than 0.750 0, and their spatical patterns were random. This suggested that there was no obvious effect of H. graminicola on M. persicae and that H. graminicola had minimal predatory effect on M. persicae.