A survey was carried out to understand the occurrence of Tetranychus urticaein Yinchuan Ningxia from May to September 2014. The results showed that as follows: the natural population dynamics of Tetranychus urticae were divided into five stages,the spatial patterns of the mite were aggregated,and the aggregation intensity decreased with increasing population density. The population began to colonize with low quantity on a few corns and low damage index in early July,increased slowly with low density and high aggregation intensity in mid-July,meanwhile the damage index and the rate of Mite corn are increased,rose quickly and distributed in whole cornfields with high density and declining aggregation intensity from the end of July to mid-August,the rate of Mite corns has reached 100%,damage index increased significantly;reached the highest with the lowest aggregation intensity in the end of August;declined quickly in September.%2014年5-9月在宁夏银川地区对二斑叶螨田间种群动态及危害情况进行调查研究.结果表明,玉米二斑叶螨田间种群动态可划分为5个阶段且均为聚集分布格局:7月上旬为种群初建期, 叶螨在玉米田刚开始发生,零星分布于玉米下部叶片,螨株率及危害指数均很低;7月中旬为种群缓慢增长期,主要分布于玉米下部以及中下部叶片, 聚集强度高, 危害指数及螨株率有所增加;7月下旬至8月中旬为种群快速增长期,此时叶螨整株分布,螨株率达 100%,种群数量高,增长迅速,聚集强度下降,危害指数显著增加;8月下旬为种群高峰期,此时叶螨田间种群数量、危害指数及螨株率均达最高;9 月以后由于玉米受害严重及玉米进入生长后期,中下部叶片大部分均已枯死,上部叶片也已老化、营养水平下降,加之气温下降,叶螨种群数量迅速下降.
展开▼
