Effects Of Landscape Pattern On Enemy Occurrence And Aphid Biocontrol In Corn Fields

North China plain is one of the major grain production areas in China,and maize is one of the major crops in north China.New type urbanization and rural land circulation are in progress,so the level of agricultural intensification will be constantly improved.Under the background of adjusting of the agricultural industrialization pattern,it is crucial to study on the relationship between agricultural landscape pattern and pest abundance and natural enemies abundance,especially the relationship between the agricultural landscape pattern and pests or natural enemies population changes,and pests catastrophe mechanism.We investigated the population dynamic of aphids,ladybeetles and parasitoids within different agricultural landscapes at whorl stage and tasseling stage of 2015 and 2016.We also identified the land use pattern by ground verification,and then compared the competition models and regression models containing landscape variables and landscape diversity with aphids or ladybeetles abundance,in order to clarify the occurrence mechanism of predators and parasitoids.The main results were as follows:1.At whorl stage,ladybeetle abundance was negatively related to maize/non-crop habitat.Propylaea japonica as the dominant ladybeetle species had the same relationship with landscape parameters as the ladybeetle complex populations.Aphid population density was negatively related to maize/other host crops.And it had extremely significantly negative correlation with predator-prey-radio,but no significant correlation with ladybeetle complex population abundance.2.At tasseling stage,ladybeetle abundance significantly increased with the rise of the maize and non-crop habitat ratio.The dominant ladybeetle species,P.japonica had the same relationship with landscape parameters as the ladybeetles abundance.And predator prey radio was positively related to non-crop habitat,while aphid abundance was negatively related to predator prey radio.So the predator prey radio was beneficial to the control aphid population.3.At whorl stage,no mummies was found,and only few mummies were found at tasseling stage,with the density of 0.091±0.047 per 100 plants and parasitism rates of 0.006±0.004%.The emerged parasitoids were morphologically identified Aphidius uzbekistanicus(Luzhetski)and Pachyneuron aphidis(Bouthe).