山地玉米植株及田间草地贪夜蛾幼虫的空间分布特征

Spatial distribution of larvae Spodoptera frugiperda (J. E. Smith) in mountainous corn plants and field

  • 摘要: 【目的】明确草地贪夜蛾幼虫在山地玉米植株上的空间分布特征,为草地贪夜蛾的预测预报、抽样调查和防治提供理论依据。【方法】以云南省曲靖市师宗县龙庆乡山地玉米种植区为调查研究点,设置系统调查田3块,每块田采用W型五点调查取样法,调查并记录不同生育期和不同部位玉米植株上草地贪夜蛾不同龄期幼虫数量;采用聚集指标、Iwao回归分析法和Taylor幂法则等方法分析山地玉米田草地贪夜蛾幼虫的空间分布格局,并基于空间分布结果,进一步拟合提出幼虫密度的理论抽样模型和基于幼虫密度防治指标的序贯抽样技术。【结果】不同生育期玉米植株上草地贪夜蛾各龄期幼虫的组成不同。除1龄幼虫在雄穗上无分布外,各龄期幼虫在玉米不同部位上均有分布,幼虫数量由大到小的分布顺序为心叶>雌穗>茎/叶>雄穗。玉米齐苗期、拔节期、大喇叭口期和吐丝期草地贪夜蛾低龄幼虫数量比例较高,分别为100.00%、71.45%、63.39%和78.07%,抽雄期、散粉期、灌浆期、乳熟期和蜡熟期草地贪夜蛾高龄幼虫数量比例较高,分别为70.01%、83.55%、81.35%、95.94%和95.56%;玉米心叶和雌穗上虫量占比较高,分别为37.73%和34.49%,其中雌穗虫量最高达237.78头/100穗;草地贪夜蛾低龄幼虫在山地玉米田呈聚集分布,高龄幼虫呈均匀分布;综合来看,山地玉米田草地贪夜蛾幼虫呈聚集分布,且聚集度具密度依赖性。基于空间分布的草地贪夜蛾低龄、高龄和全部幼虫样本的最佳理论抽样数计算模型分别为N = (\frac3.84D^2)(\frac3.2575m^2 + 0.2874)、N = (\frac3.84D^2)(\frac1.008m - 0.0644)和N = (\frac3.84D^2)(\frac1.4718m + 0.3370),基于防治指标的低龄、高龄和全部幼虫样本的序贯抽样区间计算公式分别为T_\rmIwao(n) = 0.33n \pm 1.96\sqrt 1.1063n 、T_\rmIwao(n) = 0.33n \pm 1.96\sqrt 0.3257n 和T_\rmIwao(n) = 0.33n \pm 1.96\sqrt 0.5224n 。【结论】云南山地玉米田草地贪夜蛾低龄幼虫呈聚集分布,高龄幼虫呈均匀分布,整个生育期田间草地贪夜蛾幼虫总体呈聚集分布;可通过拟合的模型计算低龄和高龄幼虫取样的最佳理论抽样数及序贯抽样区间。

     

    Abstract: 【Objective】 To clarify the spatial distribution characteristics of Spodoptera frugiperda(J. E. Smith) larvae on mountainouscorn plants, and provide basis for the prediction, sampling investigation and control of the pest.【Method】 From June to October in 2021, the population density of S. frugiperda was investigatedin the mountainous corn planting area of Longqing Township, Shizong County, Qujing City, Yunnan Province, using the W type 5-point survey sampling method in 3 maize fields, the population density of different instar larvae in different growth stages and different parts of the corn plant was recorded. The spatial distribution pattern and sampling technology of larvae were analyzed by aggrega-tion index, Iwao regression analysis method and Taylor power law. Based on the results of spatial distribution, the theoretical sampling model of larval density and the sequential sampling technique based on the control index of larval density were further fitted.【Result】The composition of larvae of S. frugiperda at each instar was different in corn plants at different growth stages. No 1st instar larvae were found on the male ear, the larvae of each instar could be found in different parts of corn. The population density of larvae S. frugiperda on corn plants followed the rank of heart leaf>cornsilk>stem/leaf> tassel. At corn seedling stage, jointing stage, big bell mouth stage and silking stage, the number proportion of young larvae of S. frugiperda was higher, which were 100.00%, 71.45%, 63.39% and 78.07% respectively. At male drawing stage, powdering stage, grain filling stage, milk mature stage and wax mature stage, the number proportion of old larvae of S. frugiperda was higher, which were 70.01%, 83.55%, 81.35%, 95.94% and 95.56% respectively.The numbers of insects on the heart leaf and female ear of corn plant were 37.73% and 34.49% respectively, of which the number of insects on 100 ears of female ear was the highest, up to 237.78 insect/100 ears. The young instar larvae of S. frugiperda were clustered in mountain corn fields;the old instar larvae were evenly distributed. The spatial distribution of all larva samples in mountain maize field showed aggregation distribution, and the aggregation degree was density dependent. The best theoretical sampling number models of young instar larvae, old instar larvae and all samples of larvae were:N = (\frac3.84D^2)(\frac3.2575m^2 + 0.2874), N = (\frac3.84D^2)(\frac1.008m - 0.0644) and N = (\frac3.84D^2)(\frac1.4718m + 0.3370). The calculation formulas of sequential sampling interval under the control indexes of samples of young instar larvae, old instar larvae and all samples of larvae were as follows:TIwao(n) =0.33n±1.96 √1.1063n, TIwao(n) =0.33n±1.96 √0.3257n and TIwao(n) =0.33n±1.96 √0.5224n.【Conclusion】The young instar larvae of S. frugiperda in Yunnan mountainous corn fields are clustered and the old instar larvae are evenly distributed. The larvae of S. frugiperda are clustered and distributed in the whole growth period. The optimal theoretical sampling number and sequential sampling interval of young and old larvae can be calculated by the fitted model.

     

/

返回文章
返回