稻田放养满江红对蚊虫孳生影响的初步观察

实验室笼内研究表明,容器水面覆盖细绿萍可阻止库蚊在其中产卵,但对中华按蚊产卵无显著作用。1987年在湖南桂东县对放养细绿萍的稻田观察结果,库蚊(主要是三带喙库蚊)幼虫密度明显比对照田为低,而且随着覆盖面积比例扩大而下降率愈大,当覆盖面积达到95％时,平均下降率达78.96％,但对按蚊幼虫密度下降率甚微,这与实验室观察结果相符。在桂东县,养萍稻田每亩可收鲜萍1500-2000公斤,可用作禽畜饲料或其他作物基肥。养萍稻田也可使稻谷增产8％左右。由于养萍既可减少库蚊幼虫孳生,也有较好的经济效益,是在稻田蚊虫综合治理中值得采用的方法之一。

CULTIVATION OF A FERN, AZOLLA FILICULOIDES IN RICE FIELDS FOR MOSQUITO CONTROL*

Results of the field observations in Guangtung County2 Hunan Province in 1987 demonstrated that cultivation of A, filiculoides in rice paddies could prevent the oviposition and hence reduce the larval density of culicine mosquitoes, mostly Culex tritaeniorhynchus. Increase of the area of Azolla-covered water surface resulted in greater reduction of the larval population. An average of 79% reduction of the culicine larval density was found when 95% of the water surface was covered with the fern. The population of Anopheles sinensis, however, was not significantly reduced. These results were in concur with that of the previous laboratory studies. As an animal feed and green manure, 22,500-30,000 kg/ha of fresh fern could be .harvested by the local farmers. It was also found that the rice yield of the fields with cultivated Azolla increased by 8%, comparing to the fields without the fern.