The Effects Of Landscape Pattern Of Wintering Habitat On The Community Structure And Potential Control Efficacy Of Egg Parasitoid Wasps Against Pine Caterpillars (Dendrolimus Spp.)

For a long time,the biological control measurements against pests has mainly focused on crop habitats,while little attention has been paid to non-crop habitats in agricultural landscapes.Due to large-area single crops planting,crop habitats are often disrupted by farming operations.Thus,the environments of crop habitats are not stable for natural enemies.Therefore,it's very important to study the potential control efficacy of parasitoid group in landscape scales.This study was conducted in the agro-ecosystem across Lingyuan county,Liaoning Province.Multi-interdisciplinary research methods such as landscape ecology,geo-statistics and molecular method were applied to estimate the effects of landscape variables on the occurrence of pests and the control effects of parasitoids in agro-ecosystems.The results will provide references for adjusting and optimizing the agricultural production structure and carrying out ecological agriculture construction,and provide theoretical basis for the conservation of natural enemies under the landscape scale and pest management utilization of Trichogramma in non-crop habitats.The main results are as follows:1.In the survey area,the proportion of farmland was the highest,which was 69.28%;followed by forest,which was 18.05%;and the proportion of man-made materials was the smallest,12.68%.The landscape diversity index ranges from 1 to 0.55 with an average of 2.21.Species of pine caterpillar egg parasitoid wasps include: Trichogrammatid spp.,Ooencyrtus spp.,Telenomus spp.,Pachyneuron spp.,Anastatus spp..Trichogrammatid spp.and Ooencyrtus spp.are the dominant species against pine caterpillar egg parasitoid wasps in this region,accounting for 54.66% and 32.06%,respectively.The parasitoid community wasn't correlatted with landscape or spatial variables.The parasitism rate,abortion rate,and diversity index of parasitoid comunity in pine caterpillar eggs was not influenced by landscape diversity index and habitat ratio.2.The parasitism proportions of Trichogrammatid spp.,Telenomus spp.,and Anastatus spp.were significantly influenced by landscape diversity index and habitat area size.The parasitism proportion of Telenomus spp.increased with landscape diversity index and habitat area size.While both parasitism proportions of Trichogrammatid spp.and Anastatus spp.decreased with landscape diversity index and habitat area size.There was a negative correlation between the parasitism rate of Trichogramma spp.and Ooencyrtus spp.,Telenomus spp.and Ooencyrtus spp.,and the Anastatus spp.and Pachyneuron spp..The total parasitism proportion of parasitoid groups was not influenced by the landscape diversity index,habitat ratio,and diversity index of parasitoid species,but it increased with parasitism rate of pine caterpillar eggs.3.The cultches of Trichogramma spp.collected from each sampling points were infected by Wolbachia.The infection rate ranged from 6.67% to 100%.The auto-correlations between Wolbachia infection rate and landscape or spatial variations were not significant in Trichogramma chilonis.However,in Trichogramma dendrolimi populations,the auto-correlation between Wolbachia infection rate and spatial variations was significant,but not significant between Wolbachia infection rate and landscape variations.The Wolbachia infection rate increased significantly with habitat area size in both Trichogramma species,but decreased significantly with landscape diversity index.The auto-correlations between male ratio or individual size and landscape or spatial variability in T.Dendrolimi were not signifcant.The brood sizes of T.dendrolimi and T.chilonis were not influenced by habitat ratio.The brood size of T.dendrolimi increased with landscape diversity index.The parasitism frequencies of T.dendrolimi and T.chilonis were not influenced by habitat ratio,but they were significantly influenced by landscape diversity index.The parasitism frequencies of T.dendrolimi decreaseed as the increase of landscape diversity index.