两种育秧方式下稻水象甲幼虫的空间分布型及其抽样技术

The spatial distribution patterns and sampling technique of Lissorhoptrus oryzophilus larvae under two seedling-raising methods

为探讨稻水象甲幼虫在贵州高原山地环境下空间分布结构,应用6种聚集度指标法和2种回归模型法,研究了旱育秧和两段式育秧方式对其空间分布型的影响。2种育秧方式稻田中稻水象甲幼虫均呈密度依赖性负二项聚集分布,基本成分是个体群,个体间相互吸引。旱育秧稻田稻水象甲幼虫聚集的原因是由环境因素所致,而两段式育秧稻田幼虫聚集的原因是由环境因素与昆虫本身聚集习性共同引发。当防治阈值为12头/丛、置信水平为1.96时,旱育秧稻田幼虫序贯抽样公式为:T1(n),T0(n)=12n±15.2943槡n;两段式育秧稻田为T1(n),T0(n)=12n±17.7580槡n,两类稻田中百丛虫量分别达到1353头和1378头以上时需要进行防治。旱育秧稻田稻水象甲幼虫最适宜的抽样方法为平行线取样法,而两段式育秧稻田则为棋盘式取样法。

The spatial distribution patterns of larvae of rice water weevil, Lissorhoptrus oryzophilus Kus- chel in mountainous region of Guizhou Plateau were studied using six aggregation indexes examination and two regressions analysis, to compare the spatial distribution differences between dry nursery seedling rai- sing and two stages seedlings-raising methods. The results indicated that the larvae of L. oryzophilus had an aggregated spatial pattern and fit to negative binomial distribution with density dependence under two seedling-raising methods. The basic component of distribution was individual group, the larvae attracted mutually among individuals. The aggregation was caused by environmental factors in dry nursery seedling field, while caused by both congregation habit of pest and environmental factors in two stages seedlings field. Under control threshold of larvae with 12 head/clump and the confidence level with 1.96, the se- quential sampling formula were T1（n） , T0（n） = 12n ± 15. 2943n for dry nursery seedling-raising and T1（n） , To（n） = 12n ± 17. 7580nfor two stages seedlings-raising, respectively. It was necessary to take actions when the larva numbers were more than 1 353 head/100 clumps in the dry nursery seedling-raising field and 1 378 head/100 clumps in the two stages seedlings-raising field, respectively. Parallel lines sam- pling was the best method for dry nursery seedling raising method, while chessboard sampling for twostages seedlings-raising method.