Dispersal effects on a discrete two-patch model for plant-insect interactions

A two-patch discrete time plant-insect model coupled through insect dispersal is studied. The model is based on three different phases: Plant growth is followed by the dispersal of insects followed by insect attacks. Our objective is to understand how different intensities of dispersal impact both local and global population dynamics of the two-patch model. Special attention is paid to two situations: When the single-patch model (i.e., in the absence of dispersal) is permanent and when the single-patch model exhibits Allee-like effects. The existence and stability of synchronous and asynchronous dynamics between two patches is explored. If the single-patch system is permanent, the permanence of the system in two patches is destroyed by extremely large dispersals and large attacking rates of insects, thus creating multiple attractors. If the single-patch model exhibits Allee-like effects, analytical and numerical results indicate that small intensity of dispersals can generate source-sink dynamics between two patches, while intermediate intensity of dispersals promote the extinction of insects in both patches for certain parameter ranges. Our study suggests a possible biology control strategy to stop the invasion of a pest by controlling its migration between patches.     

中季稻区稻田害虫—天敌—农药系统的模拟及其优化管理的研究(英文)

本文以中季稻区稻田主要害虫稻飞虱、稻纵卷叶螟和捕食天敌蜘蛛的田间系统调查资料为基础,以害虫—天敌—农药系统为研究对象,应用害虫管理系统工程的原理,处理害虫、捕食天敌与农药三者之间的关系。建立了稻纵叶螟—蜘蛛—甲胺磷和稻飞虱—蜘蛛—甲胺磷两系统优化管理模型,绘制了它们的优化反馈控制策略图,利用微机对系统进行最优监控。使用时输入当前田间害虫与天敌数量,就可对系统作出即时的预测和最优决策。该策略确立的控制害虫的最优性能指标,是使害虫对农作物的为害所造成的损失与防治费用之和最小,并且使害虫和天敌的数量处于系统平衡状态。文中比较分析了该策略与基于经济阈值的常规害虫管理策略,指出了新策略在害虫综合治理中对天敌数量进行控制和管理的作用及其意义。     

SIMULATION AND OPTIMAL MANAGEMENT OF THE PEST-NATURAL ENEMY-INSECTICIDE SYSTEM OF PADDY FIELDS IN MIDDLE SEASON RICE CROPPING REGION*

Abstract Investigations on the pest-natural enemy-insecticide system, including rice leaf roller-spider-tamaron and planthopper-spider-tamaron system, were carried out in the paddy fields in middle season rice cropping region. The relationship among insect pest, natural enemy and insecticide were studied based on the principle of the pest management system engineering. The optimal management models of the two systems were developed. Their diagrams of optimal feedback control strategy were contoured for computer monitoring of the pest-natural enemy-insecticide system. The population densities of pest and natural enemy in the future could be forecasted and the optimal strategy could be made when the current field densities of pest and natural enemy were input into the computer. The optimal performance index, which is a combination of the total cost of using the chemical and the total cost of pest damage to crops, for pest control is minimized. The objective of the system management is to drive the state of the system towards a beneficial equilibrium of the system generally. A comparison of the new IPM strategy with the ordinary strategy based on a single economic threshold is conducted in this paper. The optimal control strategies suggest that both pest and natural enemy populations should be controlled in the integrated pest management.     

Modelling pest population resurgence due to recolonization of fields following an insecticide application

1. To investigate the effect of insect recolonization on the insecticide-induced resurgence of crop pests, a modified Lotka–Volterra predator–prey model was partitioned into two areas, 'sprayed' and 'unsprayed'.
2. The unsprayed area provided a source of insects to recolonize the sprayed area, resulting in a change in pest dynamics in both areas following an insecticide application.
3. Model sensitivity to insecticide selectivity and rates of predation, insect dispersal and pest population increase were examined.
4. Resurgence risk in the sprayed area increased with increasing pest dispersal rate, but decreased with increasing predator dispersal rate.
5. Pest resurgence could also occur in the unsprayed area, especially when prey dispersal rates were low. The extent of resurgence in the unsprayed area could in some circumstances be worse than in the sprayed area itself.
6. The more efficient and longer-lived the predators, the greater the level of pest resurgence in both areas following insecticide use.
7. More selective insecticides, killing the pest, but not the predator, reduced resurgence provided that the average life-span of the predators was reasonably long. Even highly selective insecticides could cause resurgence of the pest in the unsprayed area.
8. When the prey carrying capacity of the unsprayed area was increased relative to that of the sprayed area, resurgent effects in the unsprayed area were reduced, but could still be significant under some circumstances.     

天敌昆虫抗药性研究进展

天敌昆虫抗药性研究在协调害虫化学防治和生物防治中有着重要的理论和现实意义,其研究的最终目的在于更好地推进抗性天敌在害虫综合治理(IPM)中的应用。抗药性天敌昆虫具有潜在的巨大价值。鉴于此,本文系统地综述了天敌昆虫抗药性最新研究进展,包括杀虫剂对天敌昆虫的影响、天敌昆虫抗药性现状、抗药性机理和限制天敌昆虫抗药性发展因素等。文章最后还对抗药性天敌昆虫的应用前景进行了展望。     

Comparison of management strategies for squash bugs (Hemiptera: Coreidae) in watermelon

Two watermelon pest management practices, a squash trap crop and a standard recommendation using soil-applied carbofuran, were compared using large-scale field plots to assess trap crop suitability as a replacement for the standard in 2000, 2001, and 2002. In both systems, foliar insecticide applications were used to control squash bugs when populations exceeded threshold levels. During 2001 and 2002, a treatment of untreated watermelon was used. Early season adult insects, from seedling to fruit set, are most critical for watermelon. Significantly fewer early adult bugs were found on watermelon in the trap crop than in the standard recommended practice in 1 of 3 yr. In both years, significantly fewer adult squash bugs were found in watermelon in the trap crop than in untreated fields. The standard recommended practice significantly reduced adult squash bugs in watermelon compared with the untreated in 1 of 2 yr. There was no significant correlation of watermelon yield and squash bug density, indicating that squash bug densities were too low to impact yield. Although squash bugs were reduced significantly by the trap crop, marketable watermelon yields were lower in the squash trap crop than in untreated watermelon, suggesting that pest management treatments may interfere with crop productivity factors other than squash bug colonization. Results suggest that mid-season production squash bug should be managed by monitoring populations and using insecticides as needed rather than using at-plant treatment. Further research is needed to compare treatments during early-season production.     

Implementing reduced-risk integrated pest management in fresh-market cabbage: improved net returns via scouting and timing of effective control

During 1998-2001, field studies were done to assess the efficacy of an integrated pest management (IPM) program using an action threshold and "reduced-risk" insecticides. The IPM program was compared with a conventional grower-based program. Program performance was evaluated based on management of Trichoplusia ni (Hiibner), Pieris (=Artogeia) rapae (L.), and Plutella xylostella (L.), as well as the economic impact of each program on net returns. The action threshold used in the IPM program consisted of 10% plants infested with T. ni larvae, based on previous small-plot experiment station trials. In all years of the study, the IPM program resulted in significantly lower percentages of plants infested than the conventional program or untreated check. The mean reduction in insecticide applications for the IPM program compared with the conventional program was 23.5%, whereas, on average, the costs of the IPM program were 46.0% higher than the conventional program. Pest reduction in the IPM program resulted in an average of 10.5% higher marketable yields than the conventional program. Percentages of marketable heads in the IPM program ranged from 82 to 99% and from 63 to 96% in the conventional program. Mean net returns for the IPM program exceeded the conventional program by $984.20/ha. These results indicated that the IPM program reduced insecticide use overall, even though costs of the IPM program, with either spinosad or indoxacarb, were sometimes higher. Overall, net returns of the IPM program were higher due to active pest scouting, improved application timing, and increases in marketable yield. Given the potential decrease in insecticide applications and increases in net profit resulting from this IPM program, additional analyses should be conducted to quantify the economic risk, or consistency of the results, to fully evaluate the benefits of the IPM program compared with a conventional program.     

蚜虱净对苜蓿主要害虫及天敌种群数量的影响

在甘肃省定西市九华沟系统研究了喷施蚜虱净对苜蓿主要害虫及天敌种群数量动态的影响。结果表明,施药田蚜虫和蓟马的季节平均数量极显著高于对照田,而盲蝽和瓢虫、小花蝽、蜘蛛等大多数天敌的季节平均数量则极显著低于对照田,寄生蜂与对照田没有湿著差异。喷施蚜虱净对种群数量时序动态的影响在不同害虫和天敌种类中表现不同,5月底施药后7d对照田蚜虫和蓟马的种群数量分别为施药田的4．13倍和5．2倍,此后施药田害虫的种群数量开始迅速增加,到6月底2种害虫的种群数量均与对照田无显著差异,到7月中旬以后反而显著高于对照田。施药对盲蝽种群数量时序动态的影响与蚜虫和蓟马不同,5月底施药后盲蝽的种群数量一直显著低于对照田,直到7月下旬以后,种群数量才恢复到对照田的水平。喷施蚜虱净对天敌种群数量的时序动态有极显著的影响,大多数天敌的种群数量在5月底施药后到7月底都一直显著低于对照田,直到8月上旬才恢复到对照田的水平。施用杀虫剂在防治害虫的同时杀伤大量天敌,使害虫的种群数量迅速增加,甚至造成更严重的为害。因此在菖蓿上使用对天敌杀伤力小的杀虫剂对保持天敌的自然控制能力有重要作用。     

Influence of the public's perception,attitudes, and knowledge on the implementation of integrated pest management for household insect pests

Households are mini‐ecosystems that provide a variety of conditions in which a variety of insect species can develop. Whether these insects are considered pests, largely depends on the perception, attitudes, and knowledge of the human inhabitants of the house. If considered unacceptable, residents can attempt to manage the insects themselves, or hire a professional. A pest management professional can provide a quick‐fix solution, often relying on the sole use of insecticides, or a sustainable solution through integrated pest management (IPM). In this review, it is discussed how the public's perception, attitudes, and knowledge affect the implementation of IPM in the household through the following steps: inspection, identification, establishment of a threshold level, pest control, and evaluation of effectiveness. Furthermore, recent and novel developments within the fields of inspection, identification, and pest control that allow to address pest infestations more effectively are described and their implementation in the household environment is discussed. In general, pest management in the household environment is reactive instead of pro‐active. The general public lacks the knowledge of the pest insects’ biology to identify the species, perform a proper inspection and identify causes of pest presence, as well as the knowledge of the available tools for monitoring and pest control. The percentage of individuals that seek professional aid in identification and pest control is relatively low. Moreover, the perception of and attitudes towards household insects generally result in low threshold levels. Current developments of methods for monitoring, identification, and control of insect pests in the household environment are promising, such as DNA barcoding, matrix‐assisted laser desorption/ionization time‐of‐flight and RNA interference. Efforts should be strengthened to alter the perception and attitude, and increase the knowledge of the non‐professional stakeholders, so that correct pest management decisions can be taken.     

Dispersal of potato tuber moth estimated using field application of Bt for mark-capture techniques

A new mark-capture technique involving field applications of Bacillus thuringiensis Berliner (Bt) to study the dispersal of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated as a tool to improve information on the potential impact of insect pest dispersal on crop infestation and insecticide resistance. The acquisition and persistence of Bt on moths were characterized and potential contamination of moths from naturally occurring Bts was examined. This mark-capture technique was developed to mark larger numbers of moths than had been previously achieved with laboratory marking using fluorescent dyes in mark-release-recapture experiments. Applications of commercial preparations of Bt to 0.3 and 1.0 ha potato fields were estimated to have marked ca. 50 000 moths in each experiment. Pheromone trap catches of potato tuber moths in the Bt-sprayed fields and in potato fields at distances of ca. 80, 200, 350, and 750 m were assayed for the Bt marker using selective microbiological media and identification of characteristic Bt crystal inclusions. Marking rates of moths were 78–100% in the sprayed fields and, compared with our previous mark-release-recapture studies, marking at ca. 200 m was increased by 15–18-fold to >3.0 moths per trap. This capture rate allowed the calculation of a dispersal curve that improved the reliability of estimates of movement at farm-scale distances. These estimates indicated that 10% of the population dispersed to 240 m in 3 days, and suggested that moths can potentially disperse throughout a typical potato-growing area in one growing season. This level of dispersal has implications for the spread and management of potato tuber moth populations, especially if insecticide resistance is present.     

Landscape refuges delay resistance of the European corn borer to Bt-maize: a demo-genetic dynamic model

We constructed a reaction-diffusion model of the development of resistance to transgenic insecticidal Bt crops in pest populations. Kostitzin’s demo-genetic model describes local interactions between three competing pest genotypes with alleles conferring resistance or susceptibility to transgenic plants, the spatial spread of insects being modelled by diffusion. This new approach makes it possible to combine a spatial demographic model of population dynamics with classical genetic theory. We used this model to examine the effects of pest dispersal and of the size and shape of the refuge on the efficiency of the “high-dose/refuge” strategy, which was designed to prevent the development of resistance in populations of insect pests, such as the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera, Crambidae). We found that, with realistic combinations of refuge size and pest dispersal, the development of resistance could be considerably delayed. With a small to medium-sized farming area, contiguous refuge plots are more efficient than a larger number of smaller refuge patches. We also show that the formal coupling of classical Fisher–Haldane–Wright population genetics equations with diffusion terms inaccurately describes the development of resistance in a spatially heterogeneous pest population, notably overestimating the speed with which Bt resistance is selected in populations of pests targeted by Bt crops.     

Tracking pyrethroid resistance in the polyphagous bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae), in the shifting landscape of a cotton-growing area

In cotton-growing areas of Central Africa, timing of host crops and pest management practices in annual rainfed cropping systems result in a shifting mosaic of habitats that influence the dynamics and resistance of Helicoverpa armigera (Hübner) populations on spatial scales, both within and across seasons. From 2002 to 2006, regional and local resistance was monitored among cotton fields and among the major host plants of the bollworm. From 2002, pyrethroid resistance increased within and across cotton-growing seasons to reach a worrying situation at the end of the 2005 growing season. Cotton crops played a fundamental role in the increase in seasonal resistance, even if the intensive use of insecticides on local tomato crops strongly concentrated resistance alleles in residual populations throughout the off-season. Due to the relative stability of resistance in H. armigera populations despite a long off-season, we believe that after the dispersal of the moths southwards at the end of the growing season, reverse migration mainly accounts for the reconstitution of populations at the onset of the following growing season. In addition, local resistance monitoring in 2005 and 2006 showed that it was possible to control the increase in resistance by temporarily stopping the use of pyrethroids during the period of peak infestation of cotton by H. armigera. On the other hand, the similar resistance frequency of populations sampled from sprayed and unsprayed synchronous hosts confirmed the absence of reproductive isolation between adults. As a result, diversity in cropping systems should be encouraged by planting alternative host plants to provide a mosaic of habitats, which in return would provide insecticide-free refuges. The implications for insecticide resistance management in annual cropping systems are discussed.     

The influence of management practice on the spatial distribution of Lepidopteran pests in <Emphasis Type="Italic">Brassica</Emphasis> crops in the Democratic People’s Republic of Korea: implications for sequential sampling plans

Plutella xylostella and Pieris rapae are the key components of a pest complex that attacks Brassica crops in the Democratic People’s Republic of Korea (DPRK). We examined the spatial distributions of these insects within crops both as individual species and when combined as a standard insect that was derived from their relative feeding rates. The influence of standard co-operative management practice and an integrated pest management (IPM) strategy on the dispersion of the standard insect was tested. Iwao’s m* − m relation was then used to describe the distribution of standard insects by management categories and of Pieris rapae using all data. Pest management practices only affected the distribution of the species when they were combined into standard insects. Enumerative sampling plans were therefore designed for standard insects based on population data derived from IPM-managed fields and for Pieris rapae from population data from all experimental fields. The presented plans have the potential to make a significant contribution to managing lepidopteran pests in the DPRK. The approach will be useful in the design of sequential sampling plans for other geographical regions where these pests co-occur and can also contribute to the development of sequential sampling plans for other pest complexes for which standard insects can be derived.     

我国农业害虫综合防治研究现状与展望

害虫综合防治作为农业生产的一项重要策略,在农业可持续发展中具有举足轻重的作用。近年来,针对我国害虫防治所存在的技术需求,科技部等部门先后通过973计划、863计划、科技支撑计划和农业行业专项等对重要害虫防治研究立项支持。通过这些项目的实施,我国建成了一支由国家和省级科研单位和大学组成的专业科研队伍和研究平台,对害虫监测预警技术、基于生物多样性保护利用的生态调控技术、害虫生物防治技术、化学防治技术、抗虫转基因作物利用技术等方面的研究取得了一系列的重要进展,研究建立了棉花、水稻、玉米、小麦和蔬菜等作物重要害虫的综合防治技术体系,并在农业生产中发挥了重要作用。以基因工程和信息技术为代表的第二次农业技术革命的到来,推动了害虫综合防治的理论发展,为害虫综合防治技术的广泛应用提供了新的机遇。地理信息系统、全球定位系统等信息技术和计算机网络技术的应用,提高了对害虫种群监测和预警的能力和水平,转基因抗虫作物的商业化种植等技术的应用显著增强了对害虫种群的区域性调控效率。针对产业结构调整和全球气候变化所带来的害虫新问题,进一步发展IPM新理论与新技术将成为我国农业昆虫学研究的重要方向之一。     

Spontaneous electrical activity recorded from the aphid central nervous system

Whilst many classes of insecticides target the insect central nervous system (CNS), their effects in the CNS of pest aphids have not been demonstrated. In this report, we describe an electrophysiological method for recording spontaneous neuronal activity from the giant willow aphid (Tuberolachnus salignus). Using extracellular recording electrodes and two analysis methods (threshold and template search), spontaneous spike activity was shown to exhibit sensitivity to the neuroexcitatory insecticide imidacloprid. This method allows changes in the frequency of action-potentials to be monitored during direct bath exposure to chemical agents, enabling a means of assessing and comparing neurotoxic effects of insecticides in a previously inaccessible superfamily of pest insects.     

Does Tetranychus urticae (Acari: Tetranychidae) use flying insects as vectors for phoretic dispersal?

Whether the spider mite Tetranychus urticae uses flying insects as vectors for phoretic dispersal was experimentally tested. Two bean plants were placed in a microcosm, and a mite population was introduced onto one of the plants. Either Phaenicia cuprina Wiedemann (Diptera: Calliphoridae) or Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) was then introduced into the microcosms as a hypothetical vector insect. T. urticae populations on the second bean plant were monitored to detect any evidence of phoretic dispersal. Instances of dispersal were detected at extremely low frequency, suggesting that phoretic dispersal of T. urticae mediated by winged insects is probably rare in the wild.     

The biology of insecticidal activity and resistance

Identifying insecticide resistance mechanisms is paramount for pest insect control, as the understandings that underpin insect control strategies must provide ways of detecting and managing resistance. Insecticide resistance studies rely heavily on detailed biochemical and genetic analyses. Although there have been many successes, there are also many examples of resistance that still challenge us. As a precursor to rational pest insect control, the biology of the insect, within the contexts of insecticide modes of action and insecticide metabolism, must be well understood. It makes sense to initiate this research in the best model insect system, Drosophila melanogaster, and translate these findings and methodologies to other insects. Here we explore the usefulness of the D. melanogaster model in studying metabolic-based insecticide resistances, target-site mediated resistances and identifying novel insecticide targets, whilst highlighting the importance of having a more complete understanding of insect biology for insecticide studies.     

中国棉花害虫综合防治的新进展

<正> 一、历史回顾 建国以来防治棉花害虫早已采用多种手段互为补充的综合防治。随着防治技术的发展,防治手段的重点亦随之而异。50年代后期到60年代农药的迅速发展,高效广谱农药相继出现,几乎所有主要害虫均可以用农药防治,农药遂成为防治棉虫的主要手段。由于过多地依赖农药致使一些害虫产生了抗药性。首先是棉蚜与叶螨对内吸磷和乐果的抗性,继之棉叶蝉、棉铃虫、红铃虫对滴滴涕也产生了抗性,使这些原来是高效的农药相继退出了应用市场。同时农药造成的严重环     

Monitoring Tribolium castaneum (Herbst) in pilot-scale warehouses treated with beta-cyfluthrin: are residual insecticides and trapping compatible?

Integrated pest management strategies for cereal processing facilities often include both pheromone-baited pitfall traps and crack and crevice applications of a residual insecticide such as the pyrethroid cyfluthrin. In replicated pilot-scale warehouses, a 15-week-long experiment was conducted comparing population trends suggested by insect captures in pheromone-baited traps to direct estimates obtained by sampling the food patches in untreated and cyfluthrin-treated warehouses. Warehouses were treated, provisioned with food patches and then infested with all life stages of Tribolium castaneum (Herbst). Food patches, both those initially infested and additional uninfested, were surrounded by cyfluthrin bands to evaluate if insects would cross the bands. Results show that insect captures correlated with population trends determined by direct product samples in the untreated warehouses, but not the cyfluthrin-treated warehouses. However, dead insects recovered from the floor correlated with the insect densities observed with direct samples in the cyfluthrin-treated warehouses. Initially, uninfested food patches were exploited immediately and after six weeks harbored similar infestation densities to the initially infested food patches. These data show that pest management professionals relying on insect captures in pheromone-baited traps in cyfluthrin-treated structures could be deceived into believing that a residual insecticide application was suppressing population growth, when the population was actually increasing at the same rate as an untreated population.     

CPR和P450基因在昆虫抗药性中的作用研究进展

P450酶系在昆虫代谢农药中有重要作用,NADPH-细胞色素P450还原酶（NADPH-cytochrome P450 reductase,CPR）和细胞色素P450（P450）在该酶系起核心作用。昆虫具有P450超基因家族,但只有一个单一的CPR基因,CPR是昆虫所有参与农药代谢的P450酶的唯一电子供体,其影响P450活性。P450基因的高水平表达在害虫抗药性中具有重要作用,P450基因介导的昆虫抗药性是最重要的代谢抗性类型。不同P450基因的高表达的调控机制不同,引起P450基因过量表达的原因可能有P450基因的编码区突变、顺式作用元件和反式作用因子变化、基因扩增等。细胞色素P450介导的抗药性存在一定程度的进化可塑性,即同种昆虫不同种群对相同的农药产生抗药性时,导致抗性产生的P450基因不同;同一昆虫品系在某种农药的抗性选择压力下,影响抗性的P450基因的种类和表达特性会随着持续的农药选择而发生变化。最近的研究显示,CPR的变异和昆虫抗药性相关,但是昆虫CPR基因介导抗药性的机制还缺乏深入研究。全面阐释P450酶系介导昆虫抗药性的机制、建立基于P450基因表达量变化与CPR突变的抗性分子标记,对于害虫抗药性治理具有重要意义。