幂指模型在害虫密度与作物产量损失研究中的应用

本文首次引入幂指模型 ( y=y L Mexp( - bda) )来模拟害虫密度与作物产量间的关系 ,通过对 15组不同来源的害虫与作物竞争资料的模拟 ,证明幂指模型具有实际的生物学意义 ,能准确地描述多种害虫和多种作物间的危害关系 ,预测害虫危害作物可能造成的产量损失。为害虫的经济防治提供了一种新的研究方法     

间接性害虫为害与作物产量损失的关系Ⅰ.食叶害虫

本文将繁多的农作物害虫分为间接性害虫和直接性害虫.间接性害虫造成的作物的某类器官或组织的损失率小于产量损失率.食叶害虫是间接性害虫中的一大类.作物对叶面积损失的产量反应很不一致,从完全失收到增产10倍.影响叶面积损失与产量关系的首要因素通常是作物在受害时的生长阶段.在叶面积损失率一定时,处于生长中期(最终营养库迅速增大期)的作物出现最大程度减产.在损失率过大,上部功能叶受害,为害持续时间过长,作物矮秆紧凑,水、肥及气象条件不良以及损失的叶面积分布不均匀等情形下,叶片受害后易于减产;反之则减产较少甚至增产.从分散的材料中归纳出这一基本关系,对当前广泛开展的食叶害虫的产量损失评价工作可能有参考和改进意义.     

棉田多虫复合危害互作效应及“两红”复合防治指标应用研究

针对长江中游棉区棉花多虫复合危害问题,设计了6种害虫4种组合的复合危害系统。运用通径分析方法,定量描述了多种害虫对棉花的侵害及其间的互作效应。通过多种害虫对棉花产量和品级的直接影响效应和间接影响效应分析,认为当多虫复合危害时,害虫间的相互作用就其对作物的侵害而言,表现为增强效应和减弱效应。在此基础上,研究并制定了“两红”(棉红铃虫和朱砂叶螨)复合危害动态防治指标,经验证、示范及推广应用,取得了显着的经济、生态和社会效益。     

棉田多虫复合危害互作效应及“两红”复合防治指标应用研究

针对长江中游棉区棉花多虫复合危害问题,设计了６种害虫４种组合的复合危害系统．运用通径分析方法,定量描述了多种害虫对棉花的侵害及其间的互作效应．通过多种害虫对棉花产量和品级的直接影响效应和间接影响效应分析,认为当多虫复合危害时,害虫间的相互作用就其对作物的侵害而言,表现为增强效应和减弱效应．在此基础上,研究并制定了“两红”（棉红铃虫和朱砂叶螨）复合危害动态防治指标,经验证、示范及推广应用,取得了显著的经济、生态和社会效益．     

作物——害虫——天敌系统的研究方法

作物——害虫——天敌系统包括作物——害虫、害虫——天敌两个子系统,其系统模型通过耦合两个子系统模型而建立.本文概述了系统的两种主要研究方法:作物生态学的桥梁作用以及害虫对作物的为害,目的就是为了模拟与控制系统.     

一类大尺度系统中昆虫种群时空动态模拟方法

本文介绍了一类描述大尺度作物系统害虫种群时空动态的模型,该模型包含了寄主作物,昆虫密度以及天敌间的相互作用,并简要介绍了该模型的一些模拟结果在IPM中的应用。     

973项目“重大农业害虫猖獗危害的机制及可持续控制的基础研究”简介

2006年9月,国家重点基础研究发展计划(973)农业领域2006年度项目“重大农业害虫猖獗危害的机制及可持续控制的基础研究”经科技部批准正式立项启动。该项目以全系统管理思想为指导,在基因、个体、种群、生态系统等不同层次,阐明我国重大农业害虫种群分化与暴发的分子基础,解析害虫与寄主作物及天敌间的相互作用机制,建立害虫监测与预警系统,提出重大农业害虫可持续控制的新途径和新方法,为我国农业减灾、经济的可持续发展奠定科学基础。项目的主要研究内容包括:害虫生长发育与生殖调控的分子机制;害虫对环境胁迫的适应机制;杀虫药剂诱导害虫再猖獗的机制;害虫与寄主植物的协同进化;天敌与害虫的互作及控害机制;作物-害虫-天敌食物网关系及其调控机理;重大害虫区域性暴发监测与预警。项目的总体目标为:阐明害虫生长发育、种群分化的分子基础,揭示害虫种群调节的内在机制;解析作物、害虫及天敌间的互作机制,丰富和发展植物-害虫-天敌协同进化理论;阐明主要害虫区域性灾变机理,发展害虫预警新技术;发展与环境相容的、增强自然控害功能的新技术,提出重大农业害虫可持续控制的新途径和新方法;凝炼一支害虫控制基础研究的创新团队,丰富和发展我国害虫管理的科学理论与实践,提升我国有害生物防控的原始创新和集成创新能力,扩大国际影响。     

本期重点推介

绿盲蝽Apolygus lucorum是可危害多种作物的农业害虫,在Bt棉广泛种植后,在我国北方棉区该虫呈现替代棉铃虫由次要害虫上升为主要害虫的趋势。研究和认识绿盲蝽对Bt棉的分子适应机制对其综合防治有重要意义。     

作物产量的模拟模型

产量模拟模型研究的重点是作物产量与生态因子间的关系。根据农业生态系统中限定产量的主要生态因子不同, 可将作物生产划为不同的生产水平, 并建立相应的生产力模型。各生态因子对预测不同范围的生产力都有其固有的适用性。动态模型是在长期定位观测基础上建立的, 空间变异模型用于农田产量预测, 宏观统计模型则用于区域性产量预测。本文在简要评述各类产量模型及其应用后, 提出了对产量模拟模型研究发展的看法。     

农田作物格局及其对棉花害虫波动性的影响

本文应用模糊聚类分析方法,将本地棉区1961～1987年作物群落的组合,划分成四种作物格局类型,阐述了各类型的特点及其对棉花害虫波动性的影响。基本明确作物格局与棉花害虫的关系;明确纯作棉花——两年四熟旱作和纯作棉花——两年五热水旱轮作是比较合理的种植制度;同时为长期预测棉花害虫变动趋势提供了一定的科学依据。     

Interactive effects of pests increase seed yield

Loss in seed yield and therefore decrease in plant fitness due to simultaneous attacks by multiple herbivores is not necessarily additive, as demonstrated in evolutionary studies on wild plants. However, it is not clear how this transfers to crop plants that grow in very different conditions compared to wild plants. Nevertheless, loss in crop seed yield caused by any single pest is most often studied in isolation although crop plants are attacked by many pests that can cause substantial yield losses. This is especially important for crops able to compensate and even overcompensate for the damage. We investigated the interactive impacts on crop yield of four insect pests attacking different plant parts at different times during the cropping season. In 15 oilseed rape fields in Sweden, we estimated the damage caused by seed and stem weevils, pollen beetles, and pod midges. Pest pressure varied drastically among fields with very low correlation among pests, allowing us to explore interactive impacts on yield from attacks by multiple species. The plant damage caused by each pest species individually had, as expected, either no, or a negative impact on seed yield and the strongest negative effect was caused by pollen beetles. However, seed yield increased when plant damage caused by both seed and stem weevils was high, presumably due to the joint plant compensatory reaction to insect attack leading to overcompensation. Hence, attacks by several pests can change the impact on yield of individual pest species. Economic thresholds based on single species, on which pest management decisions currently rely, may therefore result in economically suboptimal choices being made and unnecessary excessive use of insecticides.     

害虫区域性生态调控的理论、方法及实践

本文在分析害虫生态调控的生态学基础上 ,论述了害虫区域性生态调控的原理与方法 ,并以华北棉田害虫管理实践为例 ,介绍了害虫区域性生态调控的实施过程     

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.     

Many unreported crop pests and pathogens are probably already present

Invasive species threaten global biodiversity, food security and ecosystem function. Such incursions present challenges to agriculture where invasive species cause significant crop damage and require major economic investment to control production losses. Pest risk analysis (PRA) is key to prioritize agricultural biosecurity efforts, but is hampered by incomplete knowledge of current crop pest and pathogen distributions. Here, we develop predictive models of current pest distributions and test these models using new observations at subnational resolution. We apply generalized linear models (GLM) to estimate presence probabilities for 1,739 crop pests in the CABI pest distribution database. We test model predictions for 100 unobserved pest occurrences in the People's Republic of China (PRC), against observations of these pests abstracted from the Chinese literature. This resource has hitherto been omitted from databases on global pest distributions. Finally, we predict occurrences of all unobserved pests globally. Presence probability increases with host presence, presence in neighbouring regions, per capita GDP and global prevalence. Presence probability decreases with mean distance from coast and known host number per pest. The models are good predictors of pest presence in provinces of the PRC, with area under the ROC curve (AUC) values of 0.75–0.76. Large numbers of currently unobserved, but probably present pests (defined here as unreported pests with a predicted presence probability >0.75), are predicted in China, India, southern Brazil and some countries of the former USSR. We show that GLMs can predict presences of pseudoabsent pests at subnational resolution. The Chinese literature has been largely inaccessible to Western academia but contains important information that can support PRA. Prior studies have often assumed that unreported pests in a global distribution database represent a true absence. Our analysis provides a method for quantifying pseudoabsences to enable improved PRA and species distribution modelling.     

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.     

Non-crop habitats concurrently drive crop colonization by the millet head miner and regulation by natural enemies

Non-crop habitats, depending on their composition, can enhance the abundance and diversity of natural enemies of crop pests, but also at the same time provide resources to pests, thereby reducing the effect on pest incidence and resulting yield losses. The objective of the present study was to test (1) the effect of semi-natural habitats in the landscape on crop colonization by pests and natural regulation, and (2) the relationship between natural regulation and pest incidence. The pearl millet head miner (MHM) was selected as a case study because it is a key pest of millet cultivated in traditional pesticide-free tree-crop agroforestry systems in which its control mostly relies on the action of natural enemies.A set of 24 millet fields were selected in a 20×20 km area in Senegal, from the analysis of high-resolution satellite images (Pléiades), and hypotheses on the relative abundance of semi-natural habitats (here trees and rangelands) in the agricultural landscape. Millet fields were monitored for pest infestation of panicles and pest natural regulation. We used partial least squares structural equation modelling (PLS-PM) to evaluate the relationships between the abundance and diversity of semi-natural habitats at the landscape scale, crop colonization, natural pest regulation, and pest incidence.Panicle colonization by the MHM was generally high (14–92%) and increased with the abundance of trees and to a lesser extent with the rangeland area at a 1000 m-radius around millet fields. However, regulation provided by natural enemies was amplified by the abundance of trees at a local scale (250 m-radius around millet fields). This was particularly true at early crop colonization of the MHM with parasitism and direct predation on eggs and young larvae. This multi-scale effect of semi-natural habitats on crop colonization and natural regulation could explain why no clear relationship between crop colonization and pest incidence, nor natural regulation and pest incidence, was observed. Future studies on the identification of complex species-specific interactions between trees and natural enemies should provide a better understanding of the ecological processes underlying the performance of natural regulation of MHM populations.     

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.     

Genetic engineering, integrated pest management and the evolution of pests

It is well known that pest populations can evolve resistance to pesticides. The bollworm complex (Heliothis spp.), which attacks cotton plants, is a particularly good example of a highly adaptable pest. To achieve long-term success, genetic engineering projects for the production of 'insecticidal' crop plants, including cotton, need to take account of the adaptive potential of pests. Using the bollworm complex as a model, it is possible to show how an integrated approach to pest management, involving genetic engineers, evolutionary biologists and ecologists, could lead to the development of safe and effective transgenic cultivars.     

Evaluation of biorational insecticides and DNA barcoding as tools to improve insect pest management in lablab bean (Lablab purpureus) in Bangladesh

Lablab bean (Lablab purpureus) is a popular vegetable crop in Bangladesh, but farmers growing this crop experience significant losses to insect pests despite heavy reliance on conventional insecticides. We conducted field studies to improve pest management in lablab bean by testing biorational insecticides as alternatives to conventional insecticides for the control of pod borers (Maruca vitrata) and aphids (Aphis craccivora), and characterizing flower-inhabiting thrips as an emerging pest in this crop. In field experiments, spinosad was the most promising biorational we tested, suppressing pod-boring caterpillars more effectively than thiamethoxam or quinalphos. In contrast, azadirachtin (neem) did not significantly suppress any of the insect pests we measured, although target aphid populations were generally low at our research site. Using DNA barcoding at the coxI locus combined with morphological identification, we found eight thrips taxa inhabiting lablab bean flowers, dominated by Megalurothrips usitatus and M. distalis/peculiaris. A preliminary regression analysis indicated that these flower-inhabiting thrips reduced lablab bean yield. Our results suggest that spinosad may be useful within lablab bean IPM programs, and that these programs will likely need to incorporate tactics against thrips to effectively protect yield. Finally, we found that DNA barcoding was a valuable tool for pest identification in an understudied crop and region, but that to reach its full potential will require an investment in more comprehensive reference libraries.