苹果绵蚜与苹果绵蚜日光蜂种间关系的模拟研究——Ⅱ.自然系统的模拟及灵敏度分析

本文在生物学特性研究的基础上,组建了苹果绵蚜(Eriosoma lanigerum)及其日光蜂(Aphelinus mali)寄主——天敌作用系统的Boxcar train模型,对苹果绵蚜猖獗期的二种群数量进行了模拟,其结果与果园调查基本吻合。用此模型做系统的灵敏度分析,结果表明系统的内部因子(如蚜蜂的基数比例)和外部因子(温湿度)对系统均有影响。温度升高,二种群数量增加,反之则下降。湿度增加,苹果绵蚜日光蜂种群数量上升,反之则下降。湿度变化对苹果绵蚜无不良影响。比较而言,温度对系统的影响比湿度大得多。减少苹果绵蚜基数比增加日光蜂基数对系统的影响大,据此可从理论上估计生物防治的局限性。     

苹果绵蚜为害产量损失测定

苹果绵蚜为害苹果的树干、枝,新稍及根部,从中吸取大量营养,使寄主生长发育不良,产量降低。经测定苹果绵蚜发生群落数与造成的产量呈负相关,而与产量损失率成正相关,在苹果单株产量108．19～154．20kg,苹果绵蚜群落数±30～＞150个的情况下,小国光和青香蕉品种的产量损失率分别为4．10％～38．81％和7．5％～32．04％。     

苹果绵蚜防治技术研究简报

苹果绵蚜 ( Eriosoma lanigerum Hausmann)俗称绵虫、棉花虫、血色蚜虫 ,是我国规定的植物检疫性有害生物 ,也是苹果属 ( Malus)果树的重要害虫。该虫在烟台发生较普遍 ,为害较严重 ,并有逐渐向非发生地区扩散蔓延为害趋势。为寻找经济、快速、有效的防治方法 ,笔者多年进行了这方面的研究 ,取得显著的效果 ,现简报如下 :1材料与方法在山东海阳、蓬莱、莱州等选择苹果绵蚜发生较重的老果园 ,树龄 2 0 - 30年之间 ,树势中等。供试药剂为 4 0 %氧化乐果乳油 (山东张店农药厂 )。设 5个处理 ,分别是 :( 1 )涂干 :在距地面 50 cm左右的主干处 …     

苹果绵蚜生活史与防治研究

1.苹果绵蚜在青岛地区1年中最高繁殖代数为17代,平均8—9代。 2.绵蚜1年中繁殖率从6月中旬至7月中旬(22—25℃)为最高,当平均气温连续多日高达26℃以上时其繁殖率显著下降。生长季节一般低温对绵蚜总繁殖率影响不大。 3.夏季有翅蚜发生时期为5月下旬至6月下旬,为数较少,出现时期也很零散,可胎生无翅胎生绵蚜与雌雄性蚜。秋季有翅蚜自8月底开始发生,盛期在9月中旬至10月中旬,10月中旬以后即极少发生,其后代为雌雄性蚜。 4.有翅蚜无口吻,约于7—9日内脱皮4次即行交尾,雌蚜仅产卵1粒,未经交配者不产卵。性蚜自然死亡率很高(平均81.2％),在田间尚未发现有越冬卵。 5.棉蚜主要越冬场所均在其原寄生部位,如伤口、裂缝内与根部不定芽上。越冬虫态以Ⅰ、Ⅱ龄绵蚜为主。 6.绵蚜之迁移以Ⅰ龄若虫为主,5月下旬至7月中旬为主要迁移为害时期。 7.绵蚜可在苹果的萼洼内寄生为害。 8.除西洋苹果、山荆子、花红与海棠外,尚未发现绵蚜有其他寄主。 9.20倍松脂合剂加0.02％γ可湿性666或5％—6％蒽油乳剂,为防治越冬绵蚜的有效药剂。生长季节可用666乳剂或可湿性666防治。 10.666酸霉味对果实品质能引起不良影响,经初步试验其施用时期最晚不应迟于采收前1个半月至2个月。     

旅大苹果绵蚜检疫工作介绍

苹果绵蚜(Eriosoma lanigera Hausman)属半翅目蚜虫科,是国际上被列为植物检疫对象的危险性害虫之一,果树受害後,树势衰弱,产量减低,严重时全树枯死,由於绵蚜为害造成伤口,遭致其他病虫寄生为害。此虫原产於美国,在十八十九世纪曾广泛传播於欧亚各国。据记载,1930年我国首先发生於大连,後传至     

苹果绵蚜蚜小蜂——对苹果绵蚜有控制潜能的寄生蜂

苹果绵蚜蚜小蜂是苹果绵蚜的重要寄生蜂。本文综述了苹果绵蚜蚜小蜂的研究概况,包括该寄生蜂的引种与分布、寄主范围、生物学特性、控制效果与影响因素、重寄生蜂及合理利用等,指出应加快苹果绵蚜蚜小蜂的规模化生产,充分发挥其对苹果绵蚜的控制作用。     

苹果绵蚜的生物学特性及其综合治理

苹果绵蚜是一种重要的外来人侵性害虫,在世界的各苹果种植区均有分布,对苹果造成严重危害。本文主要介绍了苹果绵蚜的生物学特性、发生危害特点以及各种防治措施,包括植物检疫、农业防治、生物防治、化学防治和抗性育种等,为在我国广大果区对苹果绵蚜进行综合治理提供依据。     

温度对苹果绵蚜生长发育的影响

苹果绵蚜Eriosoma lanigerum(Hausm.)是云南苹果树的毁灭性害虫。苹果栽培面积不断扩大,由于检疫措施不严和防治工作跟不上,苹果绵蚜仍在蔓延。但云南过去未对苹果绵蚜生物学进行过系统研究。作者根据生产需要,对苹果绵蚜的有关生物学进行了观察研究。     

氧化乐果对苹果绵蚜的药效试验简报

<正> 苹果绵蚜Eriosoma lanigerum Hausmanu为害苹果树的地上部及根部,使被害部渐成瘤状,阻止了水分、养分的输导和吸收,影响花芽分化,使产量降低,一般减产20—30％,为害严重的年份,减产可高达60—70％,影响幼树枝条发育,推迟结果,甚至引起死亡。 如何防冶苹果绵蚜,是当前昆明市苹果生产上急待解决的重要课题。我们采用40％氧化乐果乳油(北京农药二厂生产),进行田间药效试验,结果简报如下:     

Age-related infection and transmission patterns of human cysticercosis

Neurocysticercosis is recognised as an important but neglected cause of epilepsy in developing countries where the parasite occurs. Data on the transmission dynamics of the parasite in endemic areas are scarce. Individuals living in these areas are likely to be highly exposed to the parasite, but relatively few of them develop active infections. The present study aimed to describe and gain insights into changes in antibody responses and infection patterns related to age and/or gender in a south Ecuadorian rural population by combining antibody and antigen serological data with demographic characteristics. In 25% of the population, antibodies to Taenia solium cysticerci were detected whilst 2.9% had circulating parasite antigens. The proportion of antibody-positive individuals increased significantly until the age of 40 years to become stable in older individuals. A rule-based simulation model was developed to explain these variations and to reflect the dynamics of exposure to, and transmission of, the parasite. In contrast, the proportion of people presenting circulating parasite antigens, reflecting an active infection, was significantly higher in people older than 60 years. Immunosenescence could explain such an observation since a weaker immune system in the elderly would facilitate the establishment and maintenance of viable cysticerci compared with fully immunocompetent younger individuals. This work points out the role of the immune system in the development of cysticercosis within an exposed population and highlights new essential issues in understanding the transmission dynamics of the parasite, its incidence and the resulting immunological response at a population level.     

Population dynamics of a vertically transmitted, parasitic sex ratio distorter and its amphipod host

We investigate the population dynamics of a vertically transmitted, parasitic sex ratio distorter ( Nosema granulosis ) and its amphipod host ( Gammarus duebeni ), using field measurements to quantify and test alternative theoretical models of the interaction. We measure parasite, host population and transmission parameters at four locations on the Isle of Cumbrae, Scotland at monthly intervals for two years. We develop a simple infinite population model and test its predictions for parasite prevalence using field measurements of the parameters. Parasite prevalence is maintained at relatively low levels at all four sites (20–42%), consistently below that predicted. The parasite imposes a slight fitness cost on its host by reducing female fecundity, but this cost cannot account for the relatively low prevalences observed. We also investigate the importance of population structure, comparing parasite prevalence across sites and sampling intervals to look for evidence of spatial and temporal asynchrony as predicted by metapopulation models. We find significant temporal and spatial heterogeneity in parasite prevalence although there was also evidence that parasite dynamics were synchronous across sites. These data suggest that the parasite is unlikely to drive local population dynamics through cycles of extinction and recolonization at the scale measured. As the host (adult) population sex ratio was male-biased, local population crashes are unlikely to be induced by the parasite, contrary to theoretical predictions.     

Population dynamics of host-parasite interactions in a cockroach-oxyuroid system

Host-parasite interactions of an urban cockroach, Blattella germanica , and its oxyuroid parasite, Blatticola blattae , were investigated. Life history data of host and parasites were collected under laboratory conditions. These data were used to model the effect of the parasite on the population dynamics of the host in order to understand the parasite's impact on the host population. The aggregation of parasites within a host was under-dispersed. Hosts normally were found to be infected with only one male and one female and rarely two or three. However, the primary sex ratio after hatching was 1.1 (males/females). Female parasite longevity equalled the life span of its host. B. blattae had a significant impact on the survival rate of the cockroach larvae and their time to reach maturity, but no effect on the survival rate of the adults. Infected host females produced fewer first oothecae than uninfected ones. Using the population parameters a simple model was developed to estimate the parasite's effect on the population dynamics of its host. According to the model the parasite suppresses the cockroach populations by ca 11%. Hence, the effect of the parasite does not appear strong enough to be used as a biological control agent by itself.     

The immunoepidemiology of nematode parasites of farmed animals: a mathematical approach.

The population dynamics of farmed animals are controlled by humans, and often involve high host densities, which encourage higher parasite burdens than would be usual in wild animals. As a result, the immunity to reinfection acquired by the host is an important determinant of parasite population dynamics. For example, lambs are highly susceptible to gastrointestinal nematodes as they begin to graze, but develop an immunity that accounts for the observed within-year variation in parasite load and pasture contamination. In the longer term, control measures are compromised by the development of parasite strains resistant to chemotherapy, focusing attention on the development of 'natural' measures, including the selection for resistant hosts and the development of antiparasite vaccines. Mick Roberts here considers the immunoepidemiology of parasites of farmed animals on three levels: the interaction between the parasite and the host's immune system determining the individual's level of protection; the development of acquired immunity determining the within-year parasite population dynamics; and the long-term effects of control measures on the between-year parasite population dynamics.     

Density dependence and the control of helminth parasites

1. The transient dynamics and stability of a population are determined by the interplay between species density, its spatial distribution and the positive and negative density-dependent processes regulating population growth. 2. Using the human-helminth parasite system as an example, we propose that the life-stage upon which negative density dependence operates will influence the rate of host reinfection following anthelmintic chemotherapy, and the likely success of control programmes. 3. Simple deterministic models are developed which highlight how a parasite species whose population size is down-regulated by density-dependent establishment will reinfect a host population at a faster rate than a species with density-dependent parasite fecundity. 4. Different forms of density dependence can produce the same equilibrium behaviour but different transient dynamics. Under-representing the nature and magnitude of density-dependent mechanisms, and in particular those operating upon establishing life-stages, may cause the resilience of the parasite population to a control perturbation to be underestimated.     

Heligmosomoides polygyrus (Nematoda): the dynamics of primary and repeated infection in outbred mice

The population dynamics of Heligmosomoides polygyrus were studied in outbred male MF1 mice subject either to primary or repeated experimental infection. Little variability in susceptibility was observed between mice, but heterogeneity increased with both duration and intensity of primary infection; this result indicates that there are differences in parasite survival between hosts. The rate of parasite-induced host mortality was 4 X 10(-4) per parasite per host per parasite lifespan. The mortality rates of male and female larvae during their development in the intestinal wall were estimated as 0.033 and 0.021 per parasite per day respectively, and estimates of the expected lifespans of the adult male and female parasites in primary infection of 11.22 and 9.92 weeks were obtained. Approximately 40% of female worms were observed in copula at any one time, although this proportion was significantly depressed in hosts harbouring fewer than 50 parasites and during the first four weeks of infection. Parasite fecundity was markedly age-dependent; each female worm produced approximately 31,000 eggs during its lifespan. No density dependence in either worm survival or fecundity in primary infection was apparent. The only detectable effect of worm density was in association with spatial distribution in the intestine; high levels of infection were associated with a posterior shift in the location of a proportion of the parasite population. Characterization of the dynamics of primary infection allowed predictions to be made about the expected dynamics of repeated infection. The comparison of predicted results and observed data revealed unequivocal epidemiological evidence for the density-dependent regulation of parasite population growth during repeated infection, affecting both parasite survival and parasite fecundity. The results also demonstrated the existence of two types of host individual in which the dynamics of repeated infection were markedly different. It is concluded that immunological differences between mice (possibly under genetic control) may be responsible for the observed effects; approximately 25% of MF1 mice seem unable to generate any protective immunity against H. polygyrus, whereas 75% become almost completely refractory to reinfection. This experimental system could be used for quantitative investigation of the impact of acquired immunity and genetic heterogeneity on helminth population dynamics. Both are of obvious relevance with respect to the control of infections of medical and veterinary significance.     

Helminth parasites of the blue-footed booby on Isla Isabel, México

A survey of the helminth fauna of the blue-footed booby, Sula nebouxii, on Isla Isabel, off the Pacific coast of México, is presented. Eight parasite species were found: 4 digeneans (Galactosomum puffini , Mesostephanus microbursa, Opisthometra planicollis, and Renicola thapari), 3 nematodes (Contracaecum sp., Porrocaecum sp., and Tetrameres sp.), and 1 cestode (Tetrabothrius sp). All these species are reported for the first time in the blue-footed booby, and they represent 8 new locality records as well. Species accumulation curves suggest these 8 parasite species comprise the total helminth fauna of this population of boobies. The most frequent and abundant parasite was R. thapari, inhabiting the kidney of its host. In male boobies, a significant negative correlation was found between abundance of R. thapari and host body condition.     

The population dynamical implications of male-biased parasitism in different mating systems

Although there is growing evidence that males tend to suffer higher levels of parasitism than females, the implications of this for the population dynamics of the host population are not yet understood. Here we build on an established 'two-sex' model and investigate how increased susceptibility to infection in males affects the dynamics, under different mating systems. We investigate the effect of pathogenic disease at different case mortalities, under both monogamous and polygynous mating systems. If the case mortality is low, then male-biased parasitism appears similar to unbiased parasitism in terms of its effect on the population dynamics. At higher case mortalities, we identified significant differences between male-biased and unbiased parasitism. A host population may therefore be differentially affected by male-biased and unbiased parasitism. The dynamical outcome is likely to depend on a complex interaction between the host's mating system and demography, and the parasite virulence.     

Importance of infection of haemosporidia blood parasites during different life history stages for long‐term reproductive fitness of collared flycatchers

The interaction between birds and haemosporidia blood parasites is a well‐used system in the study of parasite biology. However, where, when and how parasites are transmitted is often unclear and defining parasite transmission dynamics is essential because of how they influence parasite‐mediated costs to the host. In this study, we used cross‐sectional and longitudinal data taken from a collared flycatcher Ficedula albicollis population to investigate the temporal dynamics of haemosporidia parasite infection and parasite‐mediated costs to host fitness. We investigated host–parasite interactions starting at the nestling stage of the bird's life‐cycle and then followed their progress over three breeding attempts to quantify their fitness – measured as the number of offspring they produced that recruited back into the breeding population. We found that the majority of haemosporidia blood parasite infections occurred within the first year of life and that the most common parasite lineages that infected the breeding population also infected juvenile birds in the natal environment. Moreover, our findings suggest that collared flycatcher nestlings in poorer condition could be at a higher risk of haemosporidia blood parasite infection. In this study, only female and not male bird fitness was adversely affected by parasite infection and the cost of infection on female fitness depended on the timing of transmission. In conclusion, our study indicates that in collared flycatchers, early‐life is potentially important for many of the interactions with haemosporidia parasite lineages, and evidence of parasite‐mediated costs to fitness suggest that these parasites may have influenced the host population dynamics.