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一、新垦和垦种数年的湖滩灭螺效果重点调查. (一)波阳乐安草洲:系波阳湖蓄洪内湖,面积3万余亩,垦前滩地钉螺平均密度每平方市尺8.24——29.56只,最高为411只;阳性螺框占4.1%.垦种稻田后,钉螺平均密度每平方市尺减少为0——0.19只,最高密度减至16只;无螺框占95——100%,有螺面积相应缩小.阳性螺框出现率降低为0.85%.但在未经处理的水沟、水塘及漏耕滩地的钉螺,仍保持较高的密度及阳性率;其中尤以水沟为最高,钉螺平均密度每平方市尺4.96只,阳性螺出现框数占调查总框数的23.78%.
(A) Beiyang Le Ann Cao Chau: Department of Bo Yang Lake flood lakes, an area of more than 30,000 acres, Keni beach before the average density of Oncomelania snail per square City scale 8.24--29.56, the highest is 411, the positive screw frame accounts for 4.1% .After cultivation of paddy field, the average density of Oncomelania reduced to 0--0.19 per square foot, the highest density reduced to 16; Accounting for 95--100%, with a corresponding reduction of snail area, the positive rate of screw frame decreased to 0.85%, but in untreated ditches, ponds and farmland oncomelania still maintain a high density and positive rate ; Especially in the highest ditch, the average density of snails per square foot 4.96 only, the number of positive snails accounted for 23.78% of the total number of surveys.