Field margin vegetation enhances biological control and crop damage suppression from multiple pests in organic tomato fields

Ephemeral cropping systems are characterized by frequent disturbances of ecological processes, which may compromise the conservation of plant and arthropod diversity and the ecosystem services they may provide. Conservation biological control practices include habitat manipulations that provide non‐pest resources and selectively enhance natural enemies' effectiveness. This study, conducted in eight commercial fields of organically grown tomato, compared the effectiveness of sown flower strips with semi‐natural margins in regulating natural enemy abundance, biocontrol, and crop damage. During repeated visits, the abundance of different arthropod groups was recorded. Crop surveys included measurement of aphid abundance, parasitism, and leaf and fruit damage from sap‐sucking and lepidopteran pests. Semi‐natural habitats were associated with higher vegetation diversity, but natural enemies were more strongly associated with sown strips during flowering. Sap‐sucking pests were always recorded in higher abundance in flower strips, but crop damage in the plots adjacent to these strips was lower, suggesting that these strips may act as a trap‐crop. The inclusion of floral supplements enhanced the parasitism rate of aphids in the crop, and reduced the rate of increase of lepidopteran‐caused foliar damage with time. Early in the growing season, semi‐natural strips showed significantly lower levels of crop damage and aphid counts, suggesting that these habitats may be important during early crop colonization by natural enemies. These results indicate that the inclusion of flower strips enhances the conservation of arthropod functional diversity in ephemeral crops, and that diverse mechanisms are important for controlling different pests. However, the efficacy of habitat manipulation is likely to be greater when it is complemented with the conservation of diverse semi‐natural vegetation in the pre‐existing field margin.     

Biological control of tortricidae in tea fields in Japan using insect viruses and parasitoids

Tea is a perennial and evergreen plant. Cultivated tea trees provide a habitat for insect pests and their natural enemies. In Japan, granuloviruses (GVs) have successfully controlled two of the most important pests of tea, Adoxophyes honmai and Homona magnanima (Tortricidae: Lepidoptera). The GVs are produced in vivo and a single application sustains pesticidal efficacy throughout a year, which encompasses 4 to 5 discrete generations of both species. A. honmai and H. magnanima also have various natural enemies, especially hymenopteran parasitoids. Such resident natural enemies also play a role in reducing the pest density in virus-controlled fields, but the effect of virus infection on parasitoids sharing the same host larva has not been well studied. Survival of one of the major parasitoids ofA. honmai, Ascogaster reticulata (Braconidae: Hymenoptera), is reduced by virus infection of the host. Viruses, including GV and entomopoxvirus (EPV), and certain koinobiont endoparasitoids, including A. reticulata, are both known to regulate host endocrinology. However, the GV and EPV have distinct host regulation mechanisms, and consequently have different impacts on the survival of A. retuculata, when A. reticulata parasitizes a host that is infected with either GV or EPV. These additional effects on host regulation displayed by both viruses and parasitoids affect the outcome of virus-parasitoid interactions.     

Habitat manipulation to mitigate the impacts of invasive arthropod pests

Exotic invaders are some of the most serious insect pests of agricultural crops around the globe. Increasingly, the structure of landscape and habitat is recognized as having a major influence on both insect pests and their natural enemies. Habitat manipulation that aims at conserving natural enemies can potentially contribute to safer and more effective control of invasive pests. In this paper, we review habitat management experiments, published during the last 10 years, which have aimed to improve biological control of invasive pests. We then discuss during what conditions habitat management to conserve natural enemies is likely to be effective and how the likelihood of success of such methods can be improved. We finally suggest an ecologically driven research agenda for habitat management programmes.     

生境异质度对稻田捕食性天敌及水稻害虫的生态调节有效性

【目的】探索生境高异质度对稻田捕食性天敌及水稻害虫的生态调节有效性,了解这种策略是否会引起其他植食性昆虫成为水稻重要害虫的风险。【方法】2017-2018年连续2年种植单季稻,在稻田边缘种植花生与大豆,构建高异质性边缘生境稻田(rice paddy with high heterogeneous marginal habitats, HHR),调查HHR稻田与简单低异质性边缘生境稻田(rice paddy with low heterogeneous marginal habitats, LHR)中捕食性天敌与水稻害虫功能团的发生规律与相关性,计算益害比。【结果】2017年在HHR稻田中采集到捕食性天敌40种,1 667头;在LHR稻田中采集到捕食性天敌30种,991头。2018年在HHR稻田中采集到捕食性天敌33种,1 384头;在LHR稻田中采集到捕食性天敌34种,1 031头。HHR与LHR两类稻田中获得的捕食性天敌群落重要值P_i≥0.01的物种相似度很高,优势种相似。2017年HHR稻田的捕食性天敌物种丰富度明显高于LHR稻田,这种差异主要由群落重要值P_i<0.01的种类引起。2018年两类稻田的捕食性天敌物种丰富度没有差异。单位样方面积内的捕食性天敌个体数量,HHR中明显高于LHR,这种差异在2017年的分蘖期与成熟期达显著水平(P<0.05),在2018年的开花期极显著(P<0.01)。2017年在HHR中采集到水稻害虫22种,637头;在LHR中采集到水稻害虫19种,743头;物种相似性系数0.88。2018年在HHR中采集到水稻害虫16种,1 011头;在LHR中采集到水稻害虫16种,2 014头;物种相似性系数0.75;主要害虫物种组成结构相同。水稻害虫数量发生的时间动态分析表明,在分蘖期,虽然HHR稻田中的水稻害虫数量明显高于LHR(P<0.05),但此期害虫的数量不多,发生较轻。在孕穗期、开花期与成熟期,HHR稻田中的水稻害虫数量明显低于LHR稻田,这种差异在2017年的成熟期与2018年的孕穗期极显著(P<0.01),在2018年的成熟期差异显著(P<0.05)。2017年HHR和LHR中个体数量益害比N_pi值分别为2.62和1.33;2018年分别为1.37和0.51。【结论】具有高异质性边缘生境的稻田,能提高系统对捕食性天敌物种的涵养潜力,显著提高稻田捕食性天敌个体数量,提高益害比,具有更好的控制害虫的物质基础,促进捕食性天敌对水稻害虫的生态控制效能,不会引起其他植食性昆虫演变为水稻重要害虫风险,可为保护稻田生态系统天敌发挥生态效能提供可借鉴的策略与方法。     

Does experimental evolution produce better biological control agents? A critical review of the evidence

Biological control of crop pests is considered a good alternative or complement to the use of pesticides. However, legislation restricts the importation of natural enemies of pests. A potential way to circumvent this limitation is by using experimental evolution and/or artificial selection to improve native biological control agents. Here, we review studies that have used these methodologies and evaluate their success. Experimental evolution or artificial selection has been used on a wide range of traits, with most focusing on improving the performance of natural enemies in ecologically relevant environments, such as in the presence of pesticides or at different temperatures. Although most studies were poorly replicated, the selected traits generally improved following the selection process. However, correlated responses (often in the form of trade‐offs) with other traits of interest were common. We suggest that the selection procedure can be improved by increasing replication and performing experimental evolution under more semi‐natural environments, to ensure that the most useful traits are being selected.     

石菖蒲提取物对四种储粮害虫的生物活性研究

研究了石菖蒲4种溶剂无水乙醇、丙酮、乙酸乙酯、石油醚提取物对玉米象、谷蠹、长角扁谷盗和锯谷盗4种储粮害虫的驱避作用和触杀作用。结果表明：石菖蒲4种溶剂提取物对4种试虫均有明显的驱避作用和触杀作用,处理60 h的平均驱避等级均达到Ⅲ级以上,对4种试虫的触杀死亡率均达到41.11%以上。     

Commercial opportunities for pesticides based on plant essential oils in agriculture, industry and consumer products

In spite of intensive research on plant natural products and insect-plant chemical interactions over the past three decades, only two new types of botanical insecticides have been commercialized with any success in the past 15 years, those based on neem seed extracts (azadirachtin), and those based on plant essential oils. Certain plant essential oils, obtained through steam distillation and rich in mono- and sesquiterpenes and related phenols, are widely used in the flavouring and fragrance industries and in aromatherapy. Some aromatic plants have traditionally been used for stored product protection, but the potential for development of pesticides from plant essential oils for use in a wide range of pest management applications has only recently been realized. Many plant essential oils and their major terpenoid constituents are neurotoxic to insects and mites and behaviourally active at sublethal concentrations. Most plant essential oils are complex mixtures. In our laboratory we have demonstrated that individual constituents of oils rarely account for a major share of the respective oil’s toxicity. Further, our results suggest synergy among constituents, including among those that appear non-toxic in isolation. Repellent effects may be particularly useful in applications against public health and domestic pests, but may be useful in specific agricultural applications as well. In all of these applications, there is a premium on human and animal safety that takes priority over absolute efficacy. In agriculture, the main market niche for essential oil-based pesticides is in organic food production, at least in developed countries, where there are fewer competing pest management products. There is also scope for mixing these oils with conventional insecticides and for enhancing their efficacy with natural synergists. Some examples of field efficacy against agricultural pests are discussed.     

Diversity and abundance of lepidopteran stem borers and their host plants in Ethiopia

Lepidopteran stem borers are among the most important insect pests of maize, sorghum and sugarcane in sub‐Saharan Africa. Except for Chilo partellus, the other stem borer pests in Ethiopia are indigenous to Africa and are assumed to have coevolved with some native grasses and sedges in the natural habitat. In addition to pest species, natural habitats harbour diverse non‐economic stem borer species, some of which are new to science. However, with the growing threats to natural habitats, some non‐economic stem borer species may switch or expand their host ranges to include cultivated crops and evolve as “new” pests. Besides host switch, some of the unknown species currently limited to natural habitats may disappear. We examined the diversity, abundance and interactions of lepidopteran stem borers and their wild host plants in five different vegetation mosaics in Ethiopia. The stem borer species diversity varied among vegetation mosaics and host plants. Forty‐four stem borer species belonging to 14 different genera in the families of Noctuidae, Crambidae, Pyralidae and Tortricidae were recorded from 34 wild host plants and through light trap. Among these families, Noctuidae was the highest in species richness in which 31 species were identified, out of which 15 species and two genera were new to science. This paper discusses the ecological interpretation of host plant–stem borer species interactions, particularly in relation to habitat disturbances.     

生物防治利用生物多样性保护生物多样性

本文论述了生物防治与保护生物多样性的关系,提出生物多样性是生防作用物的必要来源,生物防治是保护生物多样性的重要措施。文中分析了自然界和农田生态系统中天敌的多样性和寄主专一性,并从外来种的治理、濒危物种和栖境的保护等几个方面探讨了生物防治对于保护生物多样性的作用。作者还强调应加强国际间天敌资源的交换,建立严格的天敌引种释放法规,以便开展更多的安全有效的生物防治项目。     

噻虫嗪灌根对四种叶菜上害虫的防治效果及残留检测

为明确噻虫嗪灌根对叶菜类蔬菜害虫的防治效果及残留情况,采用1.04 mg/株、1.39 mg/株和2.08 mg/株噻虫嗪对苗期快菜、青梗菜、菠菜以及叶用莴苣进行灌根处理,并调查对其主要害虫的防治效果及产品中的残留量。结果表明,在噻虫嗪有效成分为1.04 mg/株、1.39 mg/株和2.08 mg/株处理浓度下,能够将4种叶菜上的虫口数控制在2头/株以下,且产品中噻虫嗪残留量在0.0015-1.504 mg/kg,符合国际标准。因此,采用噻虫嗪有效成分1.04-2.08 mg/株的药剂浓度在苗期对叶菜类蔬菜进行灌根,可有效控制蚜虫等害虫的危害,并保证残留量符合安全标准。     

棉花耐害补偿临界指标及其应用的探讨

棉花耐害补偿反应可归纳为三种动态类型：1)不足补偿动态反应型;2)完全——不足补偿动态反应型;3)超越——完全——不足补偿动态反应型。其临界指标的建立及其应用可优化棉花病虫害综防决策．以研究害虫防治决策为例,剖析了利用害虫自然种群,人为改变害虫自然种群、人为地接放一定虫量与人工损害模拟等不同测定棉花耐害补偿能力方法的利弊。并探讨改进措施．分析论述了不同量化棉花耐害补偿能力的方法,并就棉花耐害补偿临界指标的建立及其意义作了探讨．棉花耐害补偿临界描标在棉田生态系统有害生物综合治理中可用于指导防治决策或直接用于防治决策,有着十分广阔的应用前景．最后就棉花耐害补偿临界指标及其应用的研究方向及有关问题作了讨论。     

包虫清对水稻前期害虫的控制效果及安全性

研究包虫清(有效成分：氟虫腈、杀虫单)种衣剂不同包衣方式处理水稻种子对水稻生长前期主要害虫的控制效果。结果表明,不同处理对稻蓟马、稻飞虱防治效果达90％以上,持效期达30d以上。其中包衣旱育处理对三化螟、二化螟控制效果达85％以上。包虫清种衣剂对水稻种子、植株和稻田的主要蜘蛛较安全。     

小蜂滞育的研究进展

滞育现象在多种小蜂类天敌昆虫中存在,通过研究小蜂滞育技术,可实现蜂种的长期贮存、延长防控作用时间、提高产品的抗逆性,对小蜂工厂化生产及应用具有重要意义。本文在分析国内外小蜂总科昆虫滞育文献的基础上,总结了已开展滞育研究的69种小蜂类昆虫的滞育虫态、滞育持续期、主要诱导因子以及亲代效应等,分属小蜂科、赤眼蜂科、姬小蜂科、跳小蜂科、金小蜂科、蚜小蜂科、旋小蜂、长尾小蜂科、广肩小蜂、四节小蜂科10科。小蜂多以幼虫或预蛹滞育,其滞育敏感阶段因种不同而异。滞育持续期相对较长,大多可维持数月。一种寄生麦红吸浆虫的金小蜂Macroglenes penetrans在2.5℃的土壤中,其滞育持续期可达16个月。低温、短日照和寄主是影响多数小蜂滞育的主要因子;但也有少数小蜂进行夏滞育,如普金姬小蜂Chrysocharis pubicornis、Aphelinus flavus、车轴草广肩小蜂Bruchophagus platypterus等。另外,亲代也可对小蜂滞育产生一定影响。目前,对小蜂滞育后发育生物学评价的研究报道较少,尚待进一步探索研究。     

The dominant species of natural enemies of Pentatomidae in the peak period

This paper aims to analyse how to effectively protect and scientifically utilize the natural enemies of Pentatomidae in tea plantations in the peak period. In this paper, the spatial, quantitative and temporal relationships between Pentatomidae and its natural enemies in “Pingyangtezao”, “Wuniuzao”, “Huangshandayezhong”, “Anjibaicha”,”Longjing 43″ and “Nongkangzao” tea gardens in Hefei, China were comprehensively compared and analyzed with the methods of geostatistical analysis, gray system analysis and temporal ecotone overlap index analysis. According to the size of the closeness index, the top three natural enemies with the largest sum of spatial, quantitative, and temporal closeness indexes in the six tea gardens were Clubiona japonicola (X₇, 16.514), Oxyopes sertatus (X₅, 16.390) and Xysticus ephippiafus (X₂, 16.270). The size of the ratio between the number of Pentatomidae individuals and natural enemies largely determines whether the natural enemies follow Pentatomidae pests closely or not. The better the growth of tea plantations and the richer the diversity of pest species, the more accurately the predation preference of natural enemies can be reflected. In the control of Pentatomidae, specific analysis should be made according to the occurrence characteristics of target pests in different tea plantations and the basic attributes of tea plantations (species, growth, population characteristics of natural enemies and pests, etc.) in order to scientifically utilize its natural enemies.     

Strain improvement of fungal insecticides for controlling insect pests and vector-borne diseases

Insect pathogenic fungi play an important natural role in controlling insect pests. However, few have been successfully commercialized due to low virulence and sensitivity to abiotic stresses that produce inconsistent results in field applications. These limitations are inherent in most naturally occurring biological control agents but development of recombinant DNA techniques has made it possible to significantly improve the insecticidal efficacy of fungi and their tolerance to adverse conditions, including UV. These advances have been achieved by combining new knowledge derived from basic studies of the molecular biology of these pathogens, technical developments that enable very precise regulation of gene expression, and genes encoding insecticidal proteins from other organisms, particularly spiders and scorpions. Recent coverage of genomes is helping determine the identity, origin, and evolution of traits needed for diverse lifestyles and host switching. In future, such knowledge combined with the precision and malleability of molecular techniques will allow design of multiple pathogens with different strategies and host ranges to be used for different ecosystems, and that will avoid the possibility of the host developing resistance. With increasing public concern over the continued use of synthetic chemical insecticides, these new types of biological insecticides offer a range of environmental-friendly options for cost-effective control of insect pests.     

Releases of biological control agents of insect pests on Easter Island (Pacific Ocean)

For half a century, agriculture on Easter Island has been affected by an increasing number of accidentally introduced insect pests. Due to the absence of natural enemies and other factors, these have reached high density levels which claimed for intensive use of pesticides. A project supported by the National Funds for Regional Development (FNDR) was established in 1984 to develop a biological control program against these pest species. Presently, 60 beneficial species have been introduced to control agricultural pests and flies that affect cattle and humans. Some of the natural enemies have established and are reducing pest populations thereby decreasing the requirement for insecticidal treatments. Fly density has also decreased noticeably. This can be attributed to the activity of natural enemies and dung beetles which compete with larval fly for food.     

Do weaver ants affect arthropod diversity and the natural‐enemy‐to‐pest ratio in horticultural systems?

High biodiversity is an important component of sustainable agricultural systems, and previous studies have found that increases in the diversity of the natural enemies of pests are associated with decreases in pest populations. Weaver ants are well known for their highly territorial and aggressive behaviour and for their control efficiency of many insect pests in tropical crop trees. Because of this, the ants have been used as a key component in integrated pest management (IPM) programmes for tropical crop trees. In implementing the IPM programmes, we received a number of enquiries related to whether weaver ants have negative effects on arthropod diversity and other natural enemies in orchard systems due to their aggressive behaviour. To answer these questions, we regularly sampled canopy arthropods in cashew and mango orchards in the Northern Territory of Australia in 1996, 2002 and 2003. We sampled, using a vacuum sampler, orchards with and without weaver ants. Cashew and mango plots with abundant weaver ants had similar or higher canopy arthropod and natural enemy diversity and similar ratios of natural enemies to insect pests, compared with plot where the weaver ant was absent. The study also showed that the application of insecticides reduced arthropod diversity and the ratio of natural enemies to insect pests in a mango orchard. However, insecticide spray did not affect natural enemy diversity and abundance, which may be related to a high immigration rate of natural enemies in small plots surrounded by areas that were not sprayed.     

Phytoseiid mites (Acari: Mesostigmata) associated with tea gardens in north of Iran

Predator mites of Phytoseiidae family are among the most important biocontrol agents in the world. These beneficial mites are considered as natural enemies of many pests and herbivore mites, and can feed on different growth stages of pests (egg, larva or nymph). Five species of Phytoseiidae mites were found during a survey conducted on tea plants, Camellia sinensis (Theaceae), in the Mazandaran and Guilan Provinces in the north of Iran, on the coast of the Caspian Sea, the major tea-growing region of Iran. Some of these species are recorded for the first time in tea gardens of Iran.     

Adaptive defense of pests and switching predation can improve biological control by multiple natural enemies

One of the most important questions in biological control is whether multiple natural enemies can provide greater suppression of agricultural pests than a single best enemy. Intraguild predation (IGP) among natural enemies has often been invoked to explain failure of biological control by multiple enemies, and classical theoretical studies on IGP have supported this view. However, empirical studies are inconclusive and have yielded both positive and negative results. We extend classical models by considering anti-predator behavior of pests and diet switching of omnivorous natural enemies, and examine their effects on pest control. We assume that the pest can adaptively allocate effort toward the specific defense against each predator, and that the omnivorous natural enemy can consume disproportionately more of the relatively abundant prey (switching predation) by type III functional responses to prey items. The model predicts that adaptive defense augments pests but favors introduction of multiple natural enemies for controlling pests if IGP is weak. In contrast, switching predation does not make pest control by multiple natural enemies advantageous as in classical studies, in the absence of adaptive defense. However, switching predation reduces the necessity of defense by the pest against the omnivore and offsets the effect of adaptive defense. Thus, it makes the introduction of multiple natural enemies advantageous for pest control when the pest employs adaptive defense even if IGP is strong. These results suggest that types and combinations of behavior of prey and predators may greatly affect qualitative outcomes of biological control by multiple natural enemies.     

Towards greener pastures—Pathogens and pasture pests

Two of New Zealand's most important insect pests, grass grub and porina, are endemic species which have successfully colonised improved pastures. Population densities of these insects within this new environment are far greater than in the native plant systems in which they evolved. Within these high populations diseases have flourished, and high numbers of diseases are recorded from each of these pests. These include bacteria, fungi, nematodes, viruses and protozoa. Diseases have been frequently associated with population collapses in both grass grub and porina, and the role of diseases in natural population regulation is discussed. Insect diseases can also be applied artificially and can have a useful role in pest management.