印楝素及印楝杀虫剂的安全性评价研究进展

目前开发的新农药必须具有安全性高、残留低、与环境相容的无公害的农药,从一些植物材料中分离出杀虫活性物质来防治害虫具有较长的历史和优势,从印楝中可以分离出多种对害虫具有活性的化合物如印楝素及等可以有效地控制多种害虫。自印楝素被分离鉴定以来,其广谱而独特的生物活性受到人们的广泛关注,印楝素具有良好的杀虫、拒食、驱虫、昆虫生长调节作用等多种生物活性,在农药、日化等领域都有广泛的应用;由印楝素制备的印楝杀虫制剂对害虫的广谱作用、无残留,可减缓害虫的抗药性,是用于蔬菜、果树、茶叶等作物的理想农药,已成为一种近乎完美的植物源杀虫剂。针对日益严重的农药残留及热点关注的环境安全性等问题,系统总结了印楝素及印楝杀虫剂对人、动物等的毒性及环境安全性评价,将有利于全面评价印楝杀虫剂的安全性及有效地指导印楝杀虫剂开发、生产及推广应用。     

Farmers' perceptions of constraints to plantain production in Ghana

SUMMARY

Plantain (Musa AAB), a primary food crop in Ghana, is a key component in sustainable agricultural systems in high rainfall zones. Recently, there has been a substantial yield decline and reduction in plantation life. To elucidate the context in which intervention strategies should be developed, a Participatory Rural Appraisal (PRA) was conducted at five villages in the major plantain-producing belt of Ghana. The importance of plantain as a preferred food was confirmed, although farmers tended to sell plantain for cash income, using cheaper, less preferred alternatives for home consumption. Farmers identified decreasing soil fertility, the high cost of labour for weeding, pests and diseases, lack of good quality planting material and marketing-related issues as the major production constraints. Due to declining productivity in less fertile regions, plantain has been replaced with other food crops such as cassava and maize. Farmers overestimated the importance of insect pests but were unaware of the extensive damage that could be caused by nematodes and the foliar disease, black sigatoka. They observed, however, that pest damage is more severe when soil fertility is poor. Clearly, integrated pest management is likely to be most effective when practiced within the context of cropping systems management; sustainable strategies that are being developed for resource-limited plantain farmers in Ghana are discussed.     

Brazilian free-tailed bats as insect pest regulators in transgenic and conventional cotton crops.

During the past 12000 years agricultural systems have transitioned from natural habitats to conventional agricultural regions and recently to large areas of genetically engineered (GE) croplands. This GE revolution occurred for cotton in a span of slightly more than a decade during which a switch occurred in major cotton production areas from growing 100% conventional cotton to an environment in which 95% transgenics are grown. Ecological interactions between GE targeted insects and other insectivorous insects have been investigated. However, the relationships between ecological functions (such as herbivory and ecosystem transport) and agronomic benefits of avian or mammalian insectivores in the transgenic environment generally remain unclear, although the importance of some agricultural pest management services provided by insectivorous species such as the Brazilian free-tailed bat, Tadarida brasiliensis, have been recognized. We developed a dynamic model to predict regional-scale ecological functions in agricultural food webs by using the indicators of insect pest herbivory measured by cotton boll damage and insect emigration from cotton. In the south-central Texas Winter Garden agricultural region we find that the process of insectivory by bats has a considerable impact on both the ecology and valuation of harvest in Bacillus thuringiensis (Bt) transgenic and nontransgenic cotton crops. Predation on agricultural pests by insectivorous bats may enhance the economic value of agricultural systems by reducing the frequency of required spraying and delaying the ultimate need for new pesticides. In the Winter Garden region, the presence of large numbers of insectivorous bats yields a regional summer dispersion of adult pest insects from Bt cotton that is considerably reduced from the moth emigration when bats are absent in either transgenic or non-transgenic crops. This regional decrease of pest numbers impacts insect herbivory on a transcontinental scale. With a few exceptions, we find that the agronomics of both Bt and conventional cotton production is more profitable when large numbers of insectivorous bats are present.     

SO2污染对农业害虫的间接影响

用开顶式熏气罩研究了SO2污染对粘虫、黄地老虎、小菜蛾、桃蚜、萝卜蚜和豆蚜等农业害虫的影响．结果表明，适度SO2污染显著地促进了这些昆虫的生长和／或繁殖，但高浓度SO2污染对它们有明显的不良影响，这种作用是通过食料植物间接发生的．这些昆虫对适度SO2污染的反应因种类而异：3种鳞翅目昆虫表现为幼虫的平均相对生长速率（MRGR）明显加快，成虫繁殖力变化不大；3种蚜虫主要表现为成蚜的繁殖力大幅度提高．若蚜（除豆蚜外）的MRGR也显著增加．对被处理食料植物营养成分的分析表明，SO2污染诱导的蛋氨酸相对含量变化可能是它产生这些间接影响的重要原因．     

呋喃丹降解菌CFDS-1的筛选鉴定及降解特性

为有效治理呋喃丹的污染,从受呋喃丹长期污染的土壤中分离筛选到一株高效降解呋喃丹的菌株CFDS-1,经形态、生理生化、16S rDNA(GenBank accession No.AY702969)同源性及系统发育地位等分析,将其初步鉴定为Sphingomonas sp.当接种量为5%时,CFDS-1能在48 h内降解100 mg L-1的呋喃丹,对于高达300 mg L-1的呋喃丹依然有降解效果;CFDS-1对呋喃丹的降解率与起始接种量呈正相关;降解呋喃丹的最适pH是8.0～9.0;在20～42℃范围内,温度对CFDS-1降解呋喃丹没有显著影响;该菌在250 mL三角瓶中装液量为100 mL时,对呋喃丹的降解效果最好.土壤实验表明,该菌株同样能有效地降解土壤中的呋喃丹残留.     

Dynamics of insect resistance in Bt-corn

The development of genetically modified Bt-corn, incorporating various toxin genes from Bacillus thuringiensis that act as a chemical defense against insect pests, such as the European Corn Borer, provides farmers with a new pest management option. However, the emergence of insect resistance is a threat to the continued use of Bt-corn. The United States Environment Protection Agency (US EPA) has developed planting strategies, for preventing insect resistance by planting a mixture of Bt- and non-Bt-corn. Decisions about the exact proportion of Bt- and non-Bt-corn are based on complex spatially explicit mathematical models using detailed biological assumptions about the population genetics and life history of the European Corn Borer. We develop an alternative simpler model for the spread of resistance based on the logistic growth model, which we believe has utility in situations where it is impossible or impractical to estimate the different life history and genetics parameters required by more detailed models. We use our model to investigate the US EPA’s planting rules for Bt-corn and find that short-term economic behavior is likely to lead to these rules not being followed. Our results add weight to existing work on this problem. We also investigate the economics of planting Bt-corn in markets where consumers do and do not differentiate between the modes of production for the corn. We find that Bt-corn appears to be economic in markets that do not differentiate and uneconomic in markets where consumers do differentiate.     

The semiochemically mediated interactions between bacteria and insects

In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests.     

Effects of Elevated Atmospheric Carbon Dioxide on Insect-Plant Interactions

Abstract: In the enriched carbon dioxide atmosphere expected in the next century, many species of herbivorous insects will confront less nutritious host plants that will induce both lengthened larval developmental times and greater mortality. The limited data currently available suggest that the effect of increased atmospheric CO₂ on herbivory will be not only highly species-specific but also specific to each insect-plant system. Several scenarios can be predicted, however: (1) local extinctions will occur; (2) the endangered species status as well as the pest status of some insect species will change; (3) geographic distributions for some insect species will shift with host-plant ranges; and (4) changes in the population dynamics of affected insect species will influence their interactions with other insects and plants. For insect conservation purposes, it is critical to begin long-term studies on the effects of enhanced CO₂ levels on insect populations. An analysis of the available literature indicates that many orders containing insect species important for ecosystem conservation, and even those important as agricultural or medical pests, have not been examined. Without a major increase in research on this topic, we will be unprepared for the species changes that will occur, we will lose the opportunity to document just how some insects adapt to elevated CO₂ levels, and we will lack the information necessary for effective conservation efforts.     

Avian Diversity and Functional Insectivory on North-Central Florida Farmlands

Abstract:  We studied the potential for native birds to control insect pests on farms. We assessed habitat factors correlated with diversity, distribution, and insect-foraging activity of native birds on farms in north-central Florida and then characterized common bird species that consumed insect biomass in crops as "functional insectivores" (birds most likely to contribute to pest control). Analyses of point-count survey data and foraging observations collected over 2 years on paired organic and conventional farm sites indicated that (1) farms supported most (82–96%) land birds known to breed in the region; (2) bird species richness and abundance varied significantly with matrix habitat and field border type (but not with year or farm management type); (3) the highest bird abundances were associated with mixed crop plantings, field borders, and adjacent matrix composed of forest and hedge; and (4) abundances of 10 species identified as functional insectivores were primarily influenced by crop type (mixed crops attracted significantly more insect foragers into fields than monocrops). We documented birds eating pest insects in crops and did not observe substantive crop damage by birds during growing-season observations. We advocate use of the term functional insectivore to emphasize the potential positive role of avian insectivory on farms during the growing season.     

Sustainability aspects of vegetable production in the peri-urban environment of Bogotá, Colombia

Although the peri-urban region around Bogotá, Colombia contains a diversified horticulture sector, local vegetable production suffers from a critical lack of research and availability of un-biased, scientifically validated information on crop management. In this study, we identify current trends and deficiencies in fertilisation and pest management for local vegetable production. We relate pesticide type with target pests, evaluate temporal patterns in pesticide and fertiliser use for a key crop (i.e. spinach) and conduct basic nutrient budget accounting. Personal interviews with vegetable growers were combined with a detailed follow-up of management activities and soil nutrient profiles on pilot farms in two different peri-urban municipalities. Most (84%) vegetable growers relied on personal experience, and indicated a lack of unbiased information on fertiliser effectiveness and pesticide action spectra. The majority of farmers used pesticide mixtures on a calendar basis and commonly applied products below recommended doses. Soil nutrient accounts indicate insufficient fertilisation and a progressive depletion of key nutrients. Extraction rates for the principal vegetable crops exceeded by 33.6%, 20.5% and 93.0% soil nutrient availability of N, P and K, respectively. Organic products are included in local fertilisation schemes, with chicken manure as the principal source, at an average application rate of 6 t ha^?1. Our findings could help policymakers and local institutions set a research and extension agenda to promote sustainable peri-urban vegetable production and help secure peri-urban livelihoods while ensuring healthy and safe horticultural production.     

After the flames then what? exploring the linkages between wildfires and household food security in the northern Savannah of Ghana

ABSTRACT

This study deploys the livelihoods theory in political ecology together with integrated methods including remote sensing, participatory geographic information systems, interviews and focus group discussions to explore the intricate and dynamic linkages between perennial wildfires and household food insecurity among smallholder farmers in the northern savannah zone of Ghana. Our results suggest that wildfires are a major pathway to household food insecurity in two ways, as perceived by the farmers. First, in instances where wildfires destroy the major crops of smallholders, they are unable to find enough food for the lean season which results in transitory food insecurity. Secondly, in the long term, the environmental impacts of wildfires on the soil lead to lower yields and inadequate food to meet household nutritional needs. Farmers then deploy certain strategies such as early-harvesting and switching to early-maturing crops to avoid with the perennial fires and these strategies further reinforce other dimensions of food insecurity such as nutrition insecurity. Because livelihoods strategies such as crop farming, hunting, charcoal production and herding intersect in the northern savannah zone, we recommend policy options that will engage community members in finding common ways of using shared spaces sustainably. Government should also adopt policies that will encourage domestication of certain livelihood strategies such as cattle herding.     

Identification of agricultural factors for improving sustainable land resource management in northern Thailand: A case study in Chiang Mai Province

This paper aims to identify the land-use factors benefiting sustainable land management in terms of environmental conservation. For evaluating the impacts of land use on the environment, the following parameters were used: chemical fertiliser and pesticide use, land-use structure and diversity. The farmers' income, land tenure and farming scale were selected for their influence on agricultural sustainability. The analysis shows a rapid increase in use of chemical fertiliser and pesticide in the past 40 years, and an observable increase in land-use diversity. The amount of chemical fertiliser used per unit area in large-scale farming was lower than that at small scales, but large-scale farming consumes more pesticide than small-scale farming. A significant negative correlation was observed between the proportions of the holdings possessing land and the holdings using the chemical fertiliser. In order to achieve sustainable agriculture, it is necessary to manage crop systems and land use towards selecting new strains and varieties of crops and fruits with a lower demand for chemical fertiliser and a higher resistance to disease and pests, balancing large- and small-scale farming, and ensuring land tenure and economic incentives.     

Population dynamics of farmland ladybug resources and dominant species in Nyingchi,Tibet, China北大核心CSCD

捕食性瓢虫是重要的天敌昆虫,有利于害虫的生物防治.为查清西藏林芝地区农田瓢虫资源与种群现状,明确优势种类及种群动态和规律,对林芝不同生态区域的青稞、小麦、油菜3种作物农田开展瓢虫资源调查研究,同时选取固定样地定期进行种群动态分析.结果显示:林芝地区农田瓢虫分为2个亚科4个族10个属,共13种,其中11种为捕食性瓢虫.主要优势瓢虫种类为横斑瓢虫、多异瓢虫、二星瓢虫.其中横斑瓢虫在全部调查样地中均有分布,在农田中总体优势度指数、相对多度为最高.3种优势瓢虫在不同作物中种群动态变化规律存在差异,其中横斑瓢虫虫口密度长期高于其余优势瓢虫,且与蚜虫密度曲线有较为明显的重合现象.横斑瓢虫种群密度峰值主要集中在6月中旬至7月上旬,但在不同作物农田中具体峰值时期存在差异.可见,林芝地区农田不同种类瓢虫之间有较大数量差异,在不同生态区域与作物环境下具有不同的种群特征,但是优势瓢虫种类与种群规律较为明确,可用于农田蚜虫生物防治;结果可为保护当地重要昆虫资源及开展生物防治提供基础数据支撑.(图4表6参23)     

Tracing individual movements of aphids reveals preferential routes of population transfers in agroecosystems.

Agricultural pests are not restricted to crops, but often simultaneously or successively use different cultivated and uncultivated hosts. Nevertheless, the source-sink role of cultivated and uncultivated habitats in the life cycle of crop pests remains poorly understood. This is largely due to the difficulty of tracking displacements of small organisms in agricultural landscapes. We used stable-isotope ratios in order to infer the natal host plant of individuals of the English grain aphid Sitobion avenae colonizing wheat fields in autumn. We showed that among the numerous plant sources of S. avenae, maize, which has been intensively grown in western France since the 1960s, provided most aphids that attack wheat fields early in autumn. This study illustrates how insect pests respond to land-use changes within a relatively short period of time, rapidly acquiring a new host that in turn affected their population biology considerably by playing a pivotal role on their annual life cycle.     

Multiseasonal management of an agricultural pest. I: Development of the theory

A framework for analyzing the trade-off between economic yield from a crop and buildup of resistance to pesticide caused by repeated applications of pesticide is developed. The analysis begins with the case of age-independent pest dynamics, in which pests infest a field by arriving from an external pool. Initially, it is assumed that the pest genetics of interest are single locus, two allele, with resistance to pesticide dominant and susceptible pests more fit in the absence of spraying. The pesticide is applied only once during the season, with timing and intensity of the application as control variables. Interseasonal pest and crop dynamics are studied by solving appropriate ordinary differential equations. Intraseasonal pest dynamics are assumed to follow the Hardy-Weinberg formula. It is shown that the three class diploid model can be replaced by a two class haploid model with essentially no change in the results. A model based on partial differential equations is developed, for the case in which pest dynamics depend upon age, and it is shown that the partial differential equation model can be replaced by a pair of coupled ordinary differential equations. The main operational conclusion in this paper is that the timing of the application of pesticide can be used to control buildup of resistance and that the intensity of the application can be used to control the crop yield.     

Using Citizen Science Programs to Identify Host Resistance in Pest‐Invaded Forests

Abstract: Threats to native forests from non‐native insects and pathogens (pests) are generally addressed with methods such as quarantine, eradication, biological control, and development of resistant stock through hybridization and breeding. In conjunction with such efforts, it may be useful to have citizen scientists locate rare surviving trees that may be naturally pest resistant or tolerant. The degree of resistance of individual trees identified in this way can be tested under controlled conditions, and the most resistant individuals can be integrated into plant breeding programs aimed at developing pest‐resistant native stock. Involving citizen scientists in programs aimed at identifying rare trees that survive colonization by pests provides a low‐cost means of maximizing search efforts across wide geographic regions and may provide an effective supplement to existing management approaches.     

Entomotoxic effect of silicon dioxide nanoparticles on Plutella xylostella (L.) (Lepidoptera: Plutellidae) under laboratory conditions

The use of higher dosage and repeated applications of conventional pesticides have led to the rapid development of insect resistance to pesticide and adverse effects on human health and environment. Accordingly, researchers are prompted to identify an alternative entomotoxic agent for crop protection. Nanocides are being considered as alternatives to conventional insecticides because they are expected to lessen the application rate and reduce the chances of resistance development in pests. In this study, we evaluated the entomotoxic effects of nanosilica on larvae of Plutella xylostella, in a laboratory by using dust spray, larva dipping, leaf dipping, and solution spray methods. Dust treatment showed a more highly significant effect than the other three treatments. The mortality percentage increased up to 58% and 85% at 24 and 72 h after treatment, respectively, when nanosilica was applied at a rate of 1 mg cm^?2. In all four bioassays, mortality rate increased with both increased time after nanosilica exposure and increased concentration. Light microscopy and scanning electron microscopy images showed that larval death was due to desiccation, body wall abrasion, and spiracle blockage. These results suggested that nanosilica can be an alternative to conventional pesticides if dust formulation would be properly used.     

有机磷农药生物降解研究进展

有机磷农药是目前我国使用量最大的农药 ,对农业的发展有重要的作用 ,但同时造成了严重的环境污染 .利用微生物或微生物源酶制剂来降解农药是近年来的一个主要努力方向 .至今 ,已经陆续分离到许多有机磷降解菌 ,并对其相应的降解酶的生化性质进行了鉴定 ,相关的基因也被克隆、鉴定和改造 .另外 ,基因工程及生物技术方面的进展为开发微生物或酶制品奠定了基础 .本文综述了有机磷农药降解菌、降解酶以及有机磷农药生物降解技术等方面的研究现状 .表 1参 6 1     

上海宝山钢铁厂绿化植物病虫害现状与治理对策

本文调查及分析了上海宝钢植物病虫害种类及发生情况与植物种类、植物群落配置，环境污染状况的关系，认为宝钢在植物保护工作中，应引入“IPM”病虫害综合治理技术，选择绿化树种时应考虑植物对病虫害的抗性及抗污染能力，增加群落物种组成的多样性，同时应用农业技术和生物技术控制病虫害发生程度，以减少因使用农药而造成的环境污染，维持生态平衡。