Population dynamics in changing environments: the case of an eruptive forest pest species

In recent decades we have seen rapid and co‐occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major forest pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi‐annual landscape‐wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co‐occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed‐species and age‐heterogeneous forests with good site‐matching tend to be less susceptible to large‐scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating forestry practices should be adopted as soon as possible considering the time lags involved.     

黏膜抗体在疫苗免疫效力评价中的前景

简单介绍目前疫苗效力检验的方法、黏膜抗体的功能及其在实验室疫苗效果效力评价中的应用,提出了黏膜抗体作为疫苗免疫效力试验的替代指标或免疫监测的主要抗体的建议。     

Multiple attractors of host-parasitoid models with integrated pest management strategies: eradication, persistence and outbreak

Host-parasitoid models including integrated pest management (IPM) interventions with impulsive effects at both fixed and unfixed times were analyzed with regard to host-eradication, host-parasitoid persistence and host-outbreak solutions. The host-eradication periodic solution with fixed moments is globally stable if the host’s intrinsic growth rate is less than the summation of the mean host-killing rate and the mean parasitization rate during the impulsive period. Solutions for all three categories can coexist, with switch-like transitions among their attractors showing that varying dosages and frequencies of insecticide applications and the numbers of parasitoids released are crucial. Periodic solutions also exist for models with unfixed moments for which the maximum amplitude of the host is less than the economic threshold. The dosages and frequencies of IPM interventions for these solutions are much reduced in comparison with the pest-eradication periodic solution. Our results, which are robust to inclusion of stochastic effects and with a wide range of parameter values, confirm that IPM is more effective than any single control tactic.     

Source area of spring population of meadow moth, Loxostege sticticalis L. (Lepidoptera: Pyralidae), in Northeast China

The meadow moth, Loxostege sticticalis L., is an important outbreak pest in Northeast China. The spring population in Northeast China was considered as immigrants from North China; however, the population dynamics during 1996–2007 was not consistent with this traditional theory. In this study, the source area of the spring population of the meadow moth in Northeast China was identified by trajectory analysis using the wind field simulated by mesoscale numerical forecast model MM5. The results indicated that the population of the meadow moth in North China was able to migrate into Northeast China, but had not made a crucial contribution to the outbreaks there since the weather systems were generally adverse for such a long range migration in most of the years. On the other hand, high density cocoons of L. sticticalis have frequently been found in autumn in Northeast China since 1996. The trajectory analyses indicated that most of L. sticticalis in Northeast China in spring emerged from the cocoons that had overwintered either locally or in neighboring countries, i.e. Mongolia and Russia. The development of overwintering areas at higher latitudes coincides with the increased frequency of second-generation larvae; both phenomena might be attributed to the regional climate change associated with global warming.     

Brucellosis in India — a review

Brucellosis is an important re-emerging zoonosis with a worldwide distribution. It is still an uncontrolled serious public health problem in many developing countries including India. Brucellosis in India is yet a very common but often neglected disease. Currently, Brucella melitensis accounts for most recorded cases globally with cattle emerging as a important reservoir with the few cases of B. suis. Isolated cases of non-terrestrial brucellosis and continuing transmission from wild animals have raised important epidemiological issues. Routine serological surveillance along with high clinical suspicion and screening of family members of index cases would be essential in delineating the real magnitude of human brucellosis in endemic countries. Increased business and leisure travel to endemic countries have led to diagnostic challenge in non-endemic areas. Laboratory testing is indispensable for diagnosis. Advances in newer rapid, sensitive, and specific testing methodologies and alternate treatment strategies are urgently needed. A safe and effective vaccine in human is not yet available. Prevention is dependent upon increasing public awareness through health education programmes and safe livestock practices. Active co-operation between health and veterinary services should be promoted. This review collates world literature and its impact to the discovery, isolation and diagnosis and epidemiology along with the control measures adapted in the Indian scenario.     

中国河北省卢龙县儿童轮状病毒腹泻研究

轮状病毒是我国儿童重症腹泻的主要病原。按照WHO轮状病毒监测方案,于1999年7月至2003年6月,在河北省卢龙县开展了医院和社区为基础<5岁儿童轮状病毒腹泻的监测。结果表明:卢龙县<5岁儿童腹泻的发病率为1 3次/人/年。4年中全县共有2350名<5岁急性腹泻患儿住院,占所有住院儿童的38%(2350/6213)。住院的腹泻患儿每年有两个高峰,一个是夏季(6～8月),占全年腹泻住院病例的22%;另一个在冬季(12月至次年2月),占58%。住院的轮状病毒腹泻只有一个高峰,是在冬季(12月至次年2月),高峰期的轮状病毒腹泻住院患儿数占全年轮状病毒腹泻患儿住院数的86%。按全年统计,轮状病毒腹泻占住院腹泻患儿的46%,轮状病毒腹泻的住院率为11/1000儿童/年。在门诊腹泻患儿中轮状病毒腹泻患儿占28%,在社区腹泻患儿中轮状病毒腹泻占10%。轮状病毒毒株的分布,G3型(45%)最常见,其次为G1型(35%)、G2型(8%)、G4型(3%)、G9型(0 6%),混合感染较少(1%)。还有8%的毒株未能分出型别。在轮状病毒腹泻患者中,9～11月龄的儿童检出率最高(53%),其次是12～17月龄(51%)、18～23月龄(36%)和6～8月龄(30%)。在4年研究期间共有5～10名1～59月龄儿童可能因为轮状病毒腹泻死亡,其中有1例确诊为P[8]G1型毒株感染。初步估计,该县1～59月龄儿童轮状病毒腹泻的死     

Conditions for pathogen elimination by immune systems

Summary A continuous harvest effort can lead a population to extinction. How an “unconscious” immune system would perpetrate such an effort in order to eliminate a self-replicating antigen (a pathogen) becomes an intriguing problem if the system responses are functions of the pathogen population: the responses cannot be a continuous effort as the pathogen vanishes. On theoretical grounds, we show some qualities an immune response must have to support pathogen elimination. Then, three specific mechanisms are addressed: a pathogen-independent positive feedback loop among the responding cells of the system (e.g., B-lymphocyte and T-helper); the persistence of antigen bound to presenting cells; and the programmed expansion/contraction of a pool of responding cells. The maintenance of responding cells due to these mechanisms is the essential feature to the effective clearance of self-replicating agents. Thus, evolutionarily, the primary function of a helper lymphocyte would be to amplify a response and the primary function of memory would be the very elimination of pathogens.     

Effects of insects on primary production in temperate herbaceous communities: a meta-analysis

Abstract.  1. The effects of insects on primary production in temperate herbaceous communities were investigated in a meta-analysis. The following hypotheses were tested: (1) the effect of insects on primary production depends on community type, (2) the effect of insects on primary production varies as a function of productivity, (3) insects have a greater effect on primary production in communities with low species diversity, and (4) insects have a larger effect on primary production during outbreaks.
2. Data were collected from 24 studies in which insecticides were used to suppress insects in self-sown or pastoral communities. Effect sizes were calculated from sprayed and control plot standing crop or yield, expressed as the log response ratio, ln (sprayed plot phytomass/control plot phytomass).
3. There was a significant increase in primary production as a result of insect suppression. Forb-dominated communities showed a more variable response than graminoid communities. During outbreaks, insects had a greater negative impact on primary production. Effect size was unaffected by productivity or plant species richness.
4. Although insects lower primary production in a diversity of temperate herbaceous communities, the basic measures by which such communities are often described have little effect on the proportional impact that insects have on primary production. While outbreaks are significant predictors of higher negative impact on primary production, causes of outbreaks are not always related to traits of the plant community.     

我国蝗虫暴发成灾的现状及其持续控制对策

概述并分析了我国蝗虫暴发成灾的现状及原因 ,认为全球气候变暖和区域性气候异常、人类活动的影响、监测预警技术手段落后、成灾蝗种增多和发生为害类型复杂、蝗虫研究队伍锐减及基础理论与高新技术研究滞后导致了近年来蝗虫的暴发成灾。对此 ,作者从蝗虫灾害的规律性、监测预警高新技术和综合治理技术等方面提出了实现蝗灾可持续控制的对策     

警惕沙漠蝗的猖獗发生

沙漠蝗在史前期就是北非、西亚和印度等热带荒漠地区的河谷与绿洲上的农业大害虫。我国云南和西藏自治区的聂拉木均有沙漠蝗的分布记载 ,虽尚未发生灾害 ,但是沙漠蝗猖獗发生的最大扩散区已达我国云南接壤的缅甸和西藏接壤的尼泊尔、印度。故我国的西藏自治区和云南省的有关边防及农业植物保护机构应予以高度重视并加强监测和预警 ,谨防沙漠蝗的发生危害