天敌对麦长管蚜和麦二叉蚜种群数量影响程度的分析

通过对１９９３～１９９６年两种麦蚜种群数量及其天敌数量的系统调查,并采用灰色关联分析法,研究各种天敌对两种麦蚜种群数量的影响程度,得出对麦长管蚜种群数量影响最大的是龟纹瓢虫、蚜茧蜂和食蚜蝇;对麦二叉蚜种群数量影响最大的是草间小黑蛛,其次是龟纹瓢虫．     

麦蚜与龟纹瓢虫在麦田的空间格局分析

【目的】为保护麦田天敌并合理利用天敌对麦蚜进行控制。【方法】通过田间网格式取样调查,应用生态位和地统计学方法研究了麦田中麦蚜及其主要天敌龟纹瓢虫Proplaea japonica的时空分布格局。【结果】麦蚜及瓢虫时间序列上的种群动态分析显示,麦田中龟纹瓢虫发生期比麦蚜滞后,麦蚜与龟纹瓢虫的种群数量动态趋势相似,种群相关系数为0.930,表明龟纹瓢虫与麦蚜种群呈明显的跟随关系。在空间上,麦蚜和龟纹瓢虫两者的生态位重叠度随着麦蚜的发生量增多而增高,最高达0.52。麦蚜与龟纹瓢虫的空间格局在时间序列上,随着种群数量改变而变化。在低种群密度下,麦蚜的半变异函数为线性模型,呈随机分布;在高密度下,麦蚜和龟纹瓢虫的的半变异函数均为指数模型,呈聚集分布。Block Kriging空间插值分析,得到二维空间插值模拟图,较好反映了麦蚜和龟纹瓢虫种群在麦田的时空分布。【结论】麦田生态系统中麦蚜与其天敌——龟纹瓢虫在时空分布上具有较强的相似性。同时研究结果提示,评价自然天敌对害虫的控害功能时,要综合分析两者的数量关系和空间分布关系及其控害功能的协同作用,才能提出可靠的防治策略。     

区域性农田景观格局对麦蚜及其天敌种群的生态学效应

明确农田景观格局对害虫及其天敌种群的生态学效应,是开展区域性害虫生态调控的基础.以前的研究大多集中于小空间尺度下、单个景观因子对昆虫种群的作用,而从省级范围的大空间尺度、多个景观因子的分析很少.本文以山东省区域性小麦种植区为研究对象,基于遥感影像和土地覆盖分类数据以及田间调查的昆虫种群数据,分析了景观组成类型(component type)、构成比例(component proportions)和形状结构(shape structure)多因子对麦蚜及其天敌寄生蜂和瓢虫种群的综合作用.结果发现,农田景观组成类型中斑块类型(patch type)越多,越利于麦蚜和天敌瓢虫种群数量的增长;且斑块密度(patch density)越大,越利于麦蚜寄生蜂和天敌瓢虫数量的增加;景观形状结构中边界密度(edge density)越高,也越利于麦蚜寄生蜂和天敌瓢虫种群数量的增加.进一步定量评估了农田景观组成类型、构成比例和形状结构对麦蚜及其天敌种群影响的作用大小.结果表明,三类景观格局因子对麦蚜影响较小,权重为9.81%;而对麦蚜寄生蜂的影响权重为25.87%;对天敌瓢虫种群高达47.86%.本研究清楚地表明,通过优化农田景观中作物与非作物生境布局,可直接调节和增加天敌昆虫种类与数量,有效控制和减少小麦蚜虫的种群数量,从而提高区域性农田景观中天敌昆虫的生物控害服务功能.     

植物篱对小麦蚜虫及其天敌种群的影响

采用坡地种植蓑草、苜蓿、香根草和紫穗槐等植物篱的方法,研究了其对小麦蚜虫及其天敌种群的影响.结果表明： 在20°坡度试验区,紫穗槐植物篱显著抑制了麦蚜种群的发生,且麦田拟寄生物的密度等于或显著低于香根草区.在12°坡度试验区,苜蓿和蓑草推迟了麦蚜种群发生的高峰期,蓑草作为植物篱可以显著抑制麦蚜种群数量;苜蓿区麦田拟寄生物密度显著高于对照,瓢虫种群密度等于或显著高于蓑草区.蓑草挥发物对麦长管蚜和禾谷缢管蚜均有驱避作用,而显著引诱猫蛛科1种蜘蛛;苜蓿挥发物对麦长管蚜具有引诱作用;苜蓿和蓑草挥发物对瓢虫的行为反应均无明显影响.紫穗槐和蓑草作为坡地植物篱,不仅能防护水土流失,而且有助于调控害虫及其天敌种群.     

小麦和牧草上的蚜虫与天敌种群动态及其相互关系

2008年4月底至6月初在山东禹城调查了小麦和3种牧草上的蚜虫和天敌种群密度。结果表明,麦蚜种群高峰期在5月中旬,寄生蜂和瓢虫的高峰期比蚜虫分别滞后5—10d和15～20d;麦蚜种群增长率与天敌种群密度变化呈负相关,其中与瓢虫的相关性达到显著水平;4月底至5月初小麦抽穗期是麦蚜种群爆发的关键时期,天敌密度低、害益比大是爆发的重要原因;4月底至5月初,牧草上的天敌密度是小麦上的2～3倍。牧草在麦蚜种群生态调控中具有潜在应用价值。     

七星瓢虫对两种麦蚜控制作用的模拟研究

应用二次回归旋转组合设计方法研究了七星瓢虫成虫、幼虫与两种麦蚜共存系统中瓢虫对麦长管蚜和禾谷缢管蚜的捕食量模型.结果表明七星瓢虫对两种麦蚜的捕食量随着瓢虫密度的增加而减少,随着该种麦蚜密度的增加而增加,且七星瓢虫无选择性.七星瓢虫不同个体间的干扰作用对其捕食麦长管蚜数量有显著影响,两种麦蚜数交互作用对七星瓢虫捕食禾谷缢管蚜数量影响显著.该模型可用来预测田间蚜虫的变化,指导麦田蚜虫防治.     

一类食饵种群中具有传染病的捕食-被捕食系统

对疾病仅在食饵种群传播的有比例依赖的捕食-被捕食系统的动力学进行了分析,给出了每个平衡点附近系统的性态,定义了决定疾病灭绝和成为地方病的阁值R_0．得出的结论是:在比例依赖的捕食-被捕食系统中,染病食饵种群可以充当一个生物控制量,以抑制种群的绝灭．     

红基盘瓢虫和红星盘瓢虫实验种群生命表的初步研究

本文组建了红基盘瓢虫和红星盘瓢虫的实验种群生命表,并应用Ｍｏｒｒｉｓ模式探讨影响种群数量变动的主要因子;计算了两瓢虫的内禀增长率（ｒ＿ｍ）及其它有关的生态学统计量。在实验室条件（平均温度２９．５±１．５℃和相对湿度７０．０±４．９％）下,红基盘瓢虫和红基盘瓢虫的内禀增长率（ｒ＿ｍ）、周限增长率（γ）均相近,而两者的种群趋势指数（Ｉ）、净繁殖率（Ｒ＿０）和世代平均历期（Ｔ）差异较大。红基盘瓢虫的内禀增长率ｒ＿ｍ＝０．０８４１,种群数量以每８．２天增长一倍的速率发展;红星盘瓢虫的内禀增长率ｒ＿ｍ＝０．０８８７,种群以每７．８天增长一倍的速率发展。生殖力减退是影响两瓢虫实验种群数量变动的主要因子。在盛夏进行两瓢虫的大量繁殖并应用于橄榄星室木虱的防治是可行的。     

麦蚜和寄生蜂对农业景观格局的响应及其关键景观因子分析

大量研究表明多样性的农业景观格局能够影响蚜虫及寄生蜂的分布。本文利用并设计了两种尺度的麦田农业景观格局,依据麦蚜种群发生特点,分为迁入期、增长期与高峰期三个时期,论述了不同尺度下农业景观元素对麦蚜及寄生蜂系统的影响,通过逐步回归筛选了不同时期麦蚜及寄生蜂分布的关键景观元素,最后通过CANOCO软件模拟了麦蚜及寄生蜂的分布排序格局。结果表明不同景观因子对麦蚜及寄生蜂种群影响不同,迁入期两种尺度下裸地最有利于两种有翅蚜的迁飞入田,塑料大棚对有翅蚜种群的入田有抑制作用。增长期草地与林地生境对麦蚜种群增长率促进最大,塑料大棚同样抑制了麦蚜的种群增长率;但塑料大棚、草地与林地对蚜茧蜂的种群增长率有促进作用,非麦类作物生境对蚜茧蜂种群增长率抑制作用最大;草地与林地有利于重寄生蜂的种群增长率;高峰期裸地比例大的农业景观下麦蚜的最大种群密度较大,草地与林地对蚜茧蜂与重寄生蜂的最大种群密度均有促进作用。两种尺度下的研究结果一致。不同麦物种的对不同景观元素反应与形态学与生活史特征有关,而且景观结构中特定的植物种类、非作物植物的密度与物候期都可能影响寄生蜂群落的多样性与功能。     

小种群的灭绝旋涡

小种群比大种群更易趋于灭绝.小种群迅速灭绝的三个主要原因是遗传变异性丧失、统计波动以及环境变化或自然灾害.统计波动、环境变化和遗传因子的共同效应被比作一种灭绝旋涡,它促使小种群走向灭绝.     

新疆农田系统瓢虫资源调查与多样性研究

为全面了解新疆农田系统瓢虫资源组成以及多样性结构差异,本研究采用网捕法于2018年、2019年连续两年对新疆11个地州50个县/市/区15种农作物生境的406个采集点开展了瓢虫资源系统调查.结果表明:共获7001号瓢虫标本,隶属3亚科13属26种,其中多异瓢虫Hippodamia variegata为绝对优势种类,其个...     

Soybean plant stage and population growth of soybean aphid

The soybean aphid, Aphis glycines Matsumura, is a newly invasive species of aphid in North America. Previous studies disagree as to whether soybean, Glycine max (L.) Merr., plant stage has an impact on aphid intrinsic rate of increase. Therefore, the growth rate of soybean aphids on soybean plants of different stages was examined at two different scales in the field. A planting date experiment was used to measure the population growth of soybean aphids on plants of different stages. Clip-cages were used to measure life history characteristics of individual aphids on plants of different stages. No differences were found in the population growth or dynamics of soybean aphids in the planting date experiment. The life history characteristics of individual aphids also showed no significant difference when feeding on different growth stages of soybean plants. The impact of these findings on soybean aphid management is discussed and the possible reasons why the results differ from previous estimates of the aphid growth-plant stage relationship are considered.     

Indirect Effect of a Transgenic Wheat on Aphids through Enhanced Powdery Mildew Resistance

In agricultural ecosystems, arthropod herbivores and fungal pathogens are likely to colonise the same plant and may therefore affect each other directly or indirectly. The fungus that causes powdery mildew (Blumeria graminis tritici) and cereal aphids are important pests of wheat but interactions between them have seldom been investigated. We studied the effects of powdery mildew of wheat on two cereal aphid species, Metopolophium dirhodum and Rhopalosiphum padi. We hypothesized that aphid number and size will be smaller on powdery mildew-infected plants than on non-infected plants. In a first experiment we used six commercially available wheat varieties whereas in the second experiment we used a genetically modified (GM) mildew-resistant wheat line and its non-transgenic sister line. Because the two lines differed only in the presence of the transgene and in powdery mildew resistance, experiment 2 avoided the confounding effect of variety. In both experiments, the number of M. dirhodum but not of R. padi was reduced by powdery mildew infection. Transgenic mildew-resistant lines therefore harboured bigger aphid populations than the non-transgenic lines. For both aphid species individual size was mostly influenced by aphid number. Our results indicate that plants that are protected from a particular pest (powdery mildew) became more favourable for another pest (aphids).     

Seasonal abundance of aphids (Homoptera: Aphididae) in wheat and their role as barley yellow dwarf virus vectors in the South Carolina coastal plain

Aphid (Homoptera: Aphididae) seasonal flight activity and abundance in wheat, Triticum aestivum L., and the significance of aphid species as vectors of barley yellow dwarf virus were studied over a nine-year period in the South Carolina coastal plain. Four aphid species colonized wheat in a consistent seasonal pattern. Greenbug, Schizaphis graminum (Rondani), and rice root aphid, Rhopalosiphum rufiabdominalis (Sasaki), colonized seedlingwheat immediately after crop emergence, with apterous colonies usually peaking in December or January and then declining for the remainder of the season. These two aphid species are unlikely to cause economic loss on wheat in South Carolina, thus crop managers should not have to sample for the subterranean R. rufiabdominalis colonies. Bird cherry-oat aphid, Rhopalosiphum padi (L.), was the second most abundant species and the most economically important. Rhopalosiphum padi colonies usually remained below 10/row-meter until peaking in February or March. Barley yellow dwarf incidence and wheat yield loss were significantly correlated with R. padi peak abundance and aphid-day accumulation on the crop. Based on transmission assays, R. padi was primarily responsible for vectoring the predominant virus serotype (PAV) we found in wheat. Pest management efforts should focus on sampling for and suppressing this aphid species. December planting reduced aphid-day accumulation and barley yellow dwarf incidence, but delayed planting is not a practical management option. English grain aphid, Sitobion avenae (F.), was the last species to colonize wheat each season, and the most abundant. Sitobion avenae was responsible for late-season virus transmission and caused direct yield loss by feeding on heads and flag leaves during an outbreak year.     

Comparing and contrasting life history variation in four aphid hyperparasitoids

1. In primary parasitoids, significant differences in life history and reproductive traits are observed among parasitoids attacking different stages of the same host species. Much less is known about hyperparasitoids, which attack different stages of primary parasitoids. 2. Parasitoids exploit hosts in two different ways. Koinobionts attack hosts that continue feeding and growing during parasitism, whereas idiobionts paralyse hosts before oviposition or attack non‐growing host stages, e.g. eggs or pupae. 3. Koino‐/idiobiosis in primary parasitoids are often associated with different expression of life history trade‐offs, e.g. endo‐ versus ectoparasitism, high versus low fecundity and short versus long life span. 4. In the present study, life history parameters of two koinobiont endoparasitic species (Alloxysta victrix; Syrphophagus aphidivorus), and two idiobiont ectoparasitic species (Asaphes suspensus; Dendrocerus carpenteri) of aphid hyperparasitoids were compared. These hyperparasitoids attack either the parasitoid larva in the aphid before it is killed and mummified by the primary parasitoid or the parasitoid prepupa or pupa in the dead aphid mummy. 5. There was considerable variation in reproductive success and longevity in the four species. The idiobiont A. suspensus produced the most progeny by far and had the longest lifespan. In contrast, the koinobiont A. victrix had the lowest fecundity. Other developments and life history parameters in the different species were variable. 6. The present results reveal that there was significant overlap in life history and reproductive traits among hyperparasitoid koinobionts and idiobionts, even when attacking the same host species, suggesting that selection for expression of these traits is largely association specific.     

Spatial Simulation of Epizootics Caused by Beauveria bassiana in Russian Wheat Aphid Populations

Models of disease dynamics commonly make the assumption of spatial homogeneity in the underlying host population. However, insect behavior may result in spatially heterogeneous populations with which pathogens interact. We modified a simulation model of temporal and spatial population dynamics of the Russian wheat aphid, Diuraphis noxia, on preferred or nonpreferred host plants, by incorporating effects of the entomopathogenic fungus, Beauveria bassiana. Epizootic parameters included time from inoculation of aphids until death, duration of sporulation, and estimated exposure probability. Simulations first predicted results of previously described experiments in which D. noxia adults were inoculated with conidial suspensions or water and placed on wheat or oat seedlings in 81-plant grids in cages. Subsequently, large-scale simulations were run for hypothetical field situations on 50 × 50-plant grids of wheat or oat. With B. bassiana present for both cage and larger scale simulations, results indicated that, on oat, an expanding infection front lagged behind the expanding aphid population front. Continual aphid movement from hosts resulted in many escapes, and the aphid population persisted at slightly reduced levels. On the preferred wheat host, patterns developed with pockets of infected aphids and other pockets of healthy aphids. Localized aphid populations that escaped initial infestation were able to proliferate, whereas other local populations were greatly reduced or became extinct due to lack of movement from the hosts, resulting in increased exposure to pathogen inoculum. Thus, proliferation and fluctuation of the pathogen were strongly influenced by the plant hosts' effects on aphid movement behavior. Incorporating spatial dynamics into disease models should prove useful in other efforts to predict biological control efficacy by entomopathogenic fungi in heterogeneous habitats.     

Searching for wheat resistance to aphids and wheat bulb fly in the historical Watkins and Gediflux wheat collections

Insect pests can reduce wheat yield by direct feeding and transmission of plant viruses. Here we report results from laboratory and field phenotyping studies on a wide range of wheat, including landraces from the Watkins collection deriving from before the green revolution, more modern cultivars from the Gediflux collection (north‐western Europe) and modern UK Elite varieties, for resistance to the bird cherry‐oat aphid, Rhopalosiphum padi (Homoptera: Aphididae) and the English grain aphid, Sitobion avenae (Homoptera: Aphididae). A total of 338 lines were screened for R. padi and 340 lines for S. avenae. Field trials were also conducted on 122 Watkins lines to identify wheat bulb fly, Delia coarctata, preference on these landraces. Considerable variation was shown in insect performance among and within different wheat collections, with reduced susceptibility in a number of varieties, but phenotyping did not identify strong resistance to aphids or wheat bulb fly. Field trials showed within collection differences in aphid performance, with fewer aphids populating lines from the Watkins collection. This differs from development data in laboratory bioassays and suggests that there is a pre‐alighting cue deterring aphid settlement and demonstrates differences in aphid preference and performance on older plants in the field compared with seedlings in the laboratory, highlighting the need for phenotyping for aphid resistance at different plant growth stages. No association was identified between performance of the different insect species on individual varieties, potentially suggesting different nutritional requirements or resistance mechanisms.     

On the concept of attractor for community-dynamical processes II: the case of structured populations

In Part I of this paper Jacobs and Metz (2003) extended the concept of the Conley-Ruelle, or chain, attractor in a way relevant to unstructured community ecological models. Their modified theory incorporated the facts that certain parts of the boundary of the state space correspond to the situation of at least one species being extinct and that an extinct species can not be rescued by noise. In this part we extend the theory to communities of physiologically structured populations. One difference between the structured and unstructured cases is that a structured population may be doomed to extinction and not rescuable by any biologically relevant noise before actual extinction has taken place. Another difference is that in the structured case we have to use different topologies to define continuity of orbits and to measure noise. Biologically meaningful noise is furthermore related to the linear structure of the community state space. The construction of extinction preserving chain attractors developed in this paper takes all these points into account.     

麦长管蚜和禾谷缢管蚜对小麦植株挥发物及蚜害诱导挥发物的行为反应

用四臂嗅觉计测定了麦长管蚜Macrosiphum avenae和禾谷缢管蚜Rhopalosiphum padi对小麦植株挥发物及麦蚜取食诱导挥发物的行为反应,揭示了2种麦蚜的嗅觉及小麦植株的诱导防御反应特点.在所选的13种小麦植株挥发物及蚜害诱导挥发物组分中,6-甲基-5-庚烯-2-酮、6-甲基-5-庚烯-2-醇和水杨酸甲酯对这2种蚜虫表现出强的驱拒作用;反-2-己烯醛对麦长管蚜的有翅和无翅蚜的吸引作用最强;反-2-己烯醇对禾谷缢管蚜的无翅蚜吸引作用最强,反-3-己酰醋酸酯对禾谷缢管蚜有翅蚜的吸引作用最强.说明麦蚜取食能诱导小麦植株的防御反应,麦长管蚜和禾谷缢管蚜及其不同蚜型间嗅觉反应的特点不同.