Cascade effects of crop species richness on the diversity of pest insects and their natural enemies

Understanding how plant species richness influences the diversity of herbivorous and predatory/parasitic arthropods is central to community ecology.We explore the effects of crop species richness on the diversity of pest insects and their natural enemies.Using data from a four-year experiment with five levels of crop species richness,we found that crop species richness significantly affected the pest species richness,but there were no significant effects on richness of the pests’natural enemies.In contrast,the species richness of pest insects significantly affected their natural enemies.These findings suggest a cascade effect where trophic interactions are strong between adjacent trophic levels,while the interactions between connected but nonadjacent trophic levels are weakened by the intermediate trophic level.High crop species richness resulted in a more stable arthropod community compared with communities in monoculture crops.Our results highlight the complicated cross-trophic interactions and the crucial role of crop diversity in the food webs of agro-ecosystems.     

Did maize domestication and early spread mediate the population genetics of corn leafhopper?

Investigating how crop domestication and early farming mediated crop attributes, distributions, and interactions with antagonists may shed light on today's agricultural pest problems. Crop domestication generally involved artificial selection for traits desirable to early farmers, for example, in creased productivity or yield, and enhanced qualities, though invariably it altered the interactions between crops and insects, and expanded the geographical ranges of crops. Thus, some studies suggest that with crop domestication and spread, insect populations on wild crop ancestors gave rise to pestiferous insect populations on crops. Here, we addressed whether the emergence of corn leafhopper (Dalbulus ma id is) as an agricultural pest may be associated with domestication and early spread of maize (Zea mays mays). We used AFLP markers and mitochondrial COI sequences to assess population genetic structuring and haplotype relationships among corn leafhopper samples from maize and its wild relative Zea diploperennis from multiple locations in Mexico and Argentina. We uncovered seven corn leafhopper haplotypes contained within two haplogroups, one haplogroup containing haplotypes associated with maize and the other containing haplotypes associated with Z. diploperennis in a mountainous habitat. Within the first haplogroup, one haplotype was predominant across Mexican locations, and another across Argentinean locations;both were considered pestiferous. We suggested that the divergence times of the maize-associated haplogroup and of the "pestiferous" haplotypes are correlated with the chronology of maize spread following its domestication. Overall, our results support a hypothesis positing that maize domestication favored corn leafhopper genotypes preadapted for exploiting maize so that they became pestiferous, and that with the geographical expansi on of maize farming, corn leafhopper colonized Z. diploperennis, a host exclusive to secluded habitats that serves as a refuge for archaic corn leafhopper genotypic diversity. Broadly, our results help explain the extents to which crop domestication and early spread may have mediated the emergence of today's agricultural pests.     

Can the pheromones of predators modulate responses to herbivore‐induced plant volatiles?

Biological control of greenhouse pests has been successfully developed and applied. In greenhouse crops, several entomophagous species (predators and parasitoids) are used simultaneously in the crop cycle. One important aspect of these crops, which represent modified ecosystems, is the interactions among complexes of species, including plants, phytophagous insects, and predators. The chemical relationships (semiochemicals: pheromones and kairomones) among these species likely play an important role in greenhouse crops; however, few studies have focused on these relationships. The aim of this study was to analyse the importance of semiochemicals. Three groups of laboratory trials were conducted with two predatory species: Nabis pseudoferus and Nesidiocoris tenuis (Hemiptera: Nabidae and Miridae, respectively). The results of the first group of trials indicated that the adult females of both species were more attracted to herbivore‐induced plant volatiles (HIPVs) than they were to the control plants or plants with artificial damage. Based on the second group of trials, pheromones triggered an attraction in adult females of both species for conspecifics. Finally, based on the interactions of the adult females of the same species, pheromones changed or modulated the predatory responses to HIPVs. The implications of these results for the biological control of pest species in greenhouses are further discussed.     

Effects of crop species richness on pest-natural enemy systems based on an experimental model system using a microlandscape

The relationship between crop richness and predator-prey interactions as they relate to pest-natural enemy systems is a very important topic in ecology and greatly affects biological control services. The effects of crop arrangement on predator-prey interactions have received much attention as the basis for pest population management. To explore the internal mechanisms and factors driving the relationship between crop richness and pest population management, we designed an experimental model system of a microlandscape that included 50 plots and five treatments. Each treatment had 10 repetitions in each year from 2007 to 2010. The results showed that the biomass of pests and their natural enemies increased with increasing crop biomass and decreased with decreasing crop biomass; however, the effects of plant biomass on the pest and natural enemy biomass were not significant. The relationship between adjacent trophic levels was significant (such as pests and their natural enemies or crops and pests), whereas non-adjacent trophic levels (crops and natural enemies) did not significantly interact with each other. The ratio of natural enemy/pest biomass was the highest in the areas of four crop species that had the best biological control service. Having either low or high crop species richness did not enhance the pest population management service and lead to loss of biological control. Although the resource concentration hypothesis was not well supported by our results, high crop species richness could suppress the pest population, indicating that crop species richness could enhance biological control services. These results could be applied in habitat management aimed at biological control, provide the theoretical basis for agricultural landscape design, and also suggest new methods for integrated pest management.     

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。     

Risk assessment and ecological effects of transgenic Bacillus thuringiensis crops on non-target organisms

The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.     

层次分析法在上海市农田有害生物治理中的应用

以上海市农业示范区(松江区)农药用量减少优化为例,在对其稻田农药用量现状进行调查分析的基础上,运用层次分析法的基本原理和数学模型进行了农药用量对策研究,建立了综合效益和综合代价的层次分析结构模型,将综合效益分为经济、社会、生态效益3个元素,综合代价分为经济、社会、生态代价3个元素。建立了判断矩阵,并作一致性检验,求出相应的权重;提出代价效益比RCP概念(综合代价与综合效益的比),对稻田农药用量对策进行排序,并依此作为衡量稻田农药用量的参考因子。根据分析结果,认为采用杀虫灯和施用化学农药5次(有效成分为2.23kg.hm-2)”相结合,是上海市水直播稻田有害生物的最佳防治策略。     

Spatio‐temporal analysis of plant pests in a greenhouse using a Bayesian approach

• 1 The present study aimed to propose a method that can improve our understanding of pest outbreaks and spatio‐temporal development in greenhouse crops.
• 2 The experiment was carried out in a greenhouse rose crop grown under integrated pest management (IPM) for 21 months. The main pests observed were powdery mildew, two‐spotted spider mites and western flower thrips. A quick visual sampling method was established to provide continuous monitoring of overall crop health.
• 3 A Bayesian inferential approach was then used to analyse temporal and spatial heterogeneity in the occurrence of pests. Interactions between pest dynamics and properties of spatial evolutions were exhibited revealing the influence of biotic and abiotic factors on crop health.
• 4 In the context of IPM, this information could be used to improve monitoring strategies by identifying periods or locations at risk. It could also facilitate the implementation of the whole IPM procedure through the identification of key factors that have a negative impact on overall crop health.

     

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.     

Vertical farming systems bring new considerations for pest and disease management

Vertical farming is an emerging area of food production that aims to provide sustainable intensification of agriculture by maximising the obtainable yield per unit area of land. This approach commonly utilises stacked horizontal levels of crop growth in glasshouse or controlled environment (CE) facilities. Vertical farming has, however, received relatively little scientific investigation to date. Consequently, important factors such as economic feasibility, system design and optimisation of production methods are still being evaluated. Vertical farming methods bring additional considerations for the effective management of pests and diseases compared with conventional protected horticulture, such as movement of both pest and beneficial insects between growth levels. This article aims to provide a perspective on the positive and negative issues facing pest and disease control in Vertical farming systems. We highlight important considerations for system optimisation and areas for future investigation.     

Functional Invertebrate Prey Groups Reflect Dietary Responses to Phenology and Farming Activity and Pest Control Services in Three Sympatric Species of Aerially Foraging Insectivorous Birds

Farming activity severely impacts the invertebrate food resources of farmland birds, with direct mortality to populations of above-ground arthropods thorough mechanical damage during crop harvests. In this study we assessed the effects of phenological periods, including the timing of harvest, on the composition and biomass of prey consumed by three species of aerial insectivorous birds. Common Swifts Apus apus, Barn Swallows Hirundo rustica and House Martins Delichon urbica breed sympatrically and most of their diet is obtained from agricultural sources of invertebrate prey, especially from oil-seed rape crops. We categorized invertebrate prey into six functional groups, including oil-seed rape pests; pests of other arable crops; other crop-provisioned taxa; coprophilous taxa; and taxa living in non-crop and mixed crop/non-crop habitats. Seasonality impacted functional groups differently, but the general direction of change (increase/decrease) of all groups was consistent as indexed by prey composition of the three aerial insectivores studied here. After the oil-seed rape crop harvest (mid July), all three species exhibited a dietary shift from oil-seed rape insect pests to other aerial invertebrate prey groups. However, Common Switfts also consumed a relative large quantity of oil-seed rape insect pests in the late summer (August), suggesting that they could reduce pest insect emigration beyond the host plant/crop. Since these aerially foraging insectivorous birds operate in specific conditions and feed on specific pest resources unavailable to foliage/ground foraging avian predators, our results suggest that in some crops like oil-seed rape cultivations, the potential integration of the insectivory of aerial foraging birds into pest management schemes might provide economic benefits. We advise further research into the origin of airborne insects and the role of aerial insectivores as agents of the biological control of crop insect pests, especially the determination of depredation rates and the cascading effects of insectivory on crop damage and yield.     

转基因植物对农业生物多样性的影响

论述了近年来转基因植物对农业生态系统生物多样性影响的研究进展．主要在遗传多样性、物种多样性和生态系统多样性3个层次上予以评述．包括转基因植物对作物遗传多样性的影响;转基因植物的外源基因向杂草和近缘野生种转移;转基因抗虫植物对目标害虫的影响。抗除草剂转基因植物对作物和杂草的影响,抗病毒转基因植物对病毒的影响;转基因植物对非目标生物的影响,对土壤生态系统的影响等．     

气候变暖对寒地大豆作物两种害虫发生的影响

【目的】研究温度上升对中国寒地大豆作物上植食性害虫种群发生及种间关系的影响,有利于做好田间多种害虫发生的长期预测预报。【方法】本研究在人工气候箱内模拟气候变暖,调查了低温和高温对大豆蚜Aphis glycines(Matsumura)及朱砂叶螨Tetranychus cinnabarinus(Boisduval)种群在大豆植株上的发生及二者种间关系的影响;并用"叶子圆片法"测试了两种害虫在不同大豆品种上共同发生时的相互作用影响。【结果】低温有利于大豆蚜种群发展,高温有利于朱砂叶螨的种群发生;在高温下,两种害虫的种间竞争系数下降,即环境容纳量会增大。另外,在现有的气温条件下,两种害虫在大豆上的发生关系是"偏利共存",易于共同发生的,特别是大豆蚜更易于成灾,尤其是一些感虫性比较高的当地主栽大豆品种,即不同大豆品种的抗虫性有显著差异。【结论】这些情况表明:当前寒地大豆作物上不甚严重的几种害虫在未来有较高的成灾风险,需要准备一些防控预案,譬如,选育一些抗虫性较高而又适宜本地栽种的大豆品种。     

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     

Connecting scales: Achieving in‐field pest control from areawide and landscape ecology studies

Areawide management has a long history of achieving solutions that target pests, however, there has been little focus on the areawide management of arthropod natural enemies. Landscape ecology studies that show a positive relationship between natural enemy abundance and habitat diversity demonstrate landscape‐dependent pest suppression, but have not yet clearly linked their findings to pest management or to the suite of pests associated with crops that require control. Instead the focus has often been on model systems of single pest species and their natural enemies. We suggest that management actions to capture pest control from natural enemies may be forth coming if: (i) the suite of response and predictor variables focus on pest complexes and specific management actions; (ii) the contribution of “the landscape” is identified by assessing the timing and numbers of natural enemies immigrating and emigrating to and from the target crop, as well as pests; and (iii) pest control thresholds aligned with crop development stages are the benchmark to measure impact of natural enemies on pests, in turn allowing for comparison between study regions, and generalizations. To achieve pest control we will need to incorporate what has been learned from an ecological understanding of model pest and natural enemy systems and integrate areawide landscape management with in‐field pest management.     

Soil‐dwelling insect pests of tree crops in Sub‐Saharan Africa,problems and management strategies—A review

This review aims to draw the attention of researchers, ecologists and farmers to the threats of soil‐dwelling insect pests on important tree crops in sub‐Saharan Africa, with a special focus on termites. It synthesizes the information on the effects of various factors affecting soil pest occurrence and damage, suggesting that the resultant undesirable effects of soil pests in this region are largely as a result of indiscriminate tree cutting, slash‐and‐burn agriculture and indiscriminate use of pesticides. Major insect orders, their host ranges and the nature of damage on selected tree crops are described. This study further critiques existing soil pest management practices, showing that majority of soil pest management practices are ineffective. Thus, management strategies like “attract and kill” approach based on entomopathogenic fungi need to be studied, developed and emphasized for the management of soil insect pests in sub‐Saharan Africa. A conclusion section attempts to offer suggestions for ways in which future work on soil pests in sub‐Saharan Africa could proceed.     

Changes in the distribution of multispecies pest assemblages affect levels of crop damage in warming tropical Andes

Climate induced species range shifts might create novel interactions among species that may outweigh direct climatic effects. In an agricultural context, climate change might alter the intensity of competition or facilitation interactions among pests with, potentially, negative consequences on the levels of damage to crop. This could threaten the productivity of agricultural systems and have negative impacts on food security, but has yet been poorly considered in studies. In this contribution, we constructed and evaluated process‐based species distribution models for three invasive potato pests in the Tropical Andean Region. These three species have been found to co‐occur and interact within the same potato tuber, causing different levels of damage to crop. Our models allowed us to predict the current and future distribution of the species and therefore, to assess how damage to crop might change in the future due to novel interactions. In general, our study revealed the main challenges related to distribution modeling of invasive pests in highly heterogeneous regions. It yielded different results for the three species, both in terms of accuracy and distribution, with one species surviving best at lower altitudes and the other two performing better at higher altitudes. As to future distributions our results suggested that the three species will show different responses to climate change, with one of them expanding to higher altitudes, another contracting its range and the other shifting its distribution to higher altitudes. These changes will result in novel areas of co‐occurrence and hence, interactions of the pests, which will cause different levels of damage to crop. Combining population dynamics and species distribution models that incorporate interspecific trade‐off relationships in different environments revealed a powerful approach to provide predictions about the response of an assemblage of interacting species to future environmental changes and their impact on process rates.     

The impact of secondary pests on Bacillus thuringiensis (Bt) crops

The intensification of agriculture and the development of synthetic insecticides enabled worldwide grain production to more than double in the last third of the 20th century. However, the heavy dependence and, in some cases, overuse of insecticides has been responsible for negative environmental and ecological impacts across the globe, such as a reduction in biodiversity, insect resistance to insecticides, negative effects on nontarget species (e.g. natural enemies) and the development of secondary pests. The use of recombinant DNA technology to develop genetically engineered insect‐resistant crops could mitigate many of the negative side effects of insecticides. One such genetic alteration enables crops to express toxic crystalline (Cry) proteins from the soil bacteria Bacillus thuringiensis (Bt). Despite the widespread adoption of Bt crops, there are still a range of unanswered questions concerning longer term agro‐ecosystem interactions. For instance, insect species that are not susceptible to the expressed toxin can develop into secondary pests and cause significant damage to the crop. Here, we review the main causes surrounding secondary pest dynamics in Bt crops and the impact of such outbreaks. Regardless of the causes, if nonsusceptible secondary pest populations exceed economic thresholds, insecticide spraying could become the immediate solution at farmers’ disposal, and the sustainable use of this genetic modification technology may be in jeopardy. Based on the literature, recommendations for future research are outlined that will help to improve the knowledge of the possible long‐term ecological trophic interactions of employing this technology.     

Fitness costs associated with Cry1F resistance in the European corn borer

Crops producing insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are widely planted to manage insect pests. Bt crops can provide an effective tool for pest management; however, the evolution of Bt resistance can diminish this benefit. The European corn borer, Ostrinia nubilalis Hübner, is a significant pest of maize and is widely managed with Bt maize in the Midwest of the United States. When Bt crops are grown in conjunction with non‐Bt refuges, fitness costs of Bt resistance can delay the evolution of resistance. Importantly, fitness costs often vary with ecological factors, including host‐plant genotype and diapause. In this study, we examined fitness costs associated with Cry1F resistance in O. nubilalis when insects were reared on three maize lines. Fitness costs were tested in two experiments. One experiment assessed the fitness costs when Cry1F‐resistant and Cry1F‐susceptible insects were reared on plants as larvae and experienced diapause. The second experiment tested resistant, susceptible and F1 heterozygotes that were reared on plants but did not experience diapause. Despite some evidence of greater adult longevity for Cry1F‐resistant insects, these insects produced fewer fertile eggs than Cry1F‐susceptible insects, and this occurred independent of diapause. Reduced fecundity was not detected among heterozygous individuals, which indicated that this fitness cost was recessive. Additionally, maize lines did not affect the magnitude of this fitness cost. The lower fitness of Cry1F‐resistant O. nubilalis may contribute to the maintenance of Cry1F susceptibility in field populations more than a decade after Cry1F maize was commercialized.     

农田景观格局变化对昆虫的生态学效应

景观格局变化是全球变化的一个重要内容。农田是由人类赖以生存所种植的人工栽培作物组成的生态系统。在该景观系统中,多种植物-害虫-天敌相互作用、相互制约,形成有机整体。研究农田景观格局对害虫和天敌种群动态影响,不仅在害虫生物防治的实践中有重要意义,而且对于揭示人类活动对生物多样性结构与功能的影响,阐明农田景观中生物多样性整合、维持机理有重大的理论意义。本文从农田景观格局的"质、量、形、度"4个方面,系统地论述了农田景观格局变化对害虫和天敌的作用,分析了农田景观的生物控制服务功能,指出了未来研究发展的方向。