Can microbial-based insecticides replace chemical pesticides in agricultural production?

Extensive use of chemical insecticides to control insect pests in agriculture has improved yields and production of high-quality food products. However, chemical insecticides have been shown to be harmful also to beneficial insects and many other organisms like vertebrates. Thus, there is a need to replace those chemical insecticides by other control methods in order to protect the environment. Insect pest pathogens, like bacteria, viruses or fungi, are interesting alternatives for production of microbial-based insecticides to replace the use of chemical products in agriculture. Organic farming, which does not use chemical pesticides for pest control, relies on integrated pest management techniques and in the use of microbial-based insecticides for pest control. Microbial-based insecticides require precise formulation and extensive monitoring of insect pests, since they are highly specific for certain insect pests and in general are more effective for larval young instars. Here, we analyse the possibility of using microbial-based insecticides to replace chemical pesticides in agricultural production.     

Plant essential oils: a substitute for conventional insecticides against Tribolium species (Coleoptera: Tenebrionidae)-achievements and challenges

Abstract

The literature on efficacy of plant essential oils and their constituents for the management of Tribolium spp. (T. castaneum and T. confusum), instigating infestation of a variety of stored grains and their products is reviewed here. Both species caused significant losses in the diverse food grains and their products through infestation. Essential oils of higher plants showed potential activity in the management of these infestation driven losses. Researchers have found that essential oils and their chemical constituents have significant toxicity against both the species of Tribolium via different modes of action like repellent, insecticidal, ovicidal, larvicidal, pupicidal, ovipositional and feeding deterrent actions. Concerning repellency and in vivo bioassays, few studies have been done with the essential oils against T. confusum, thus, more investigations are required to find the repellent agents against this insect. There are some essential oil-based botanical insecticides which have been proved effective for the protection of food grains from both beetles during storage. These botanical insecticides also exhibited behaviour altering properties against both beetles, thus, reducing the problem of pest resistance which is a problem with conventional insecticides. Therefore, essential oils-based botanical insecticides may be preferred option than conventional insecticides for protecting stored grains and their products against Tribolium infestation.     

Toxic effects of some insecticides,herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae)

Cereals are staple food for many countries and are grown on millions of hectares of land, but much of the harvest is wasted due to losses by pests. To minimize these losses, many pesticides are used which are damaging to the environment and human health. There are debates to get rid of these chemicals but they are still in use at large scale. An alternative control strategy for insect pests in storage houses is the use of botanicals. In this study, four plant essential oils, two plant extracts, two herbicides, and two insecticides were used against Tribolium confusum and the comparison of toxicity was made by calculating LC₅₀ and LT₅₀ values. LC₅₀ values were higher for abamectin (2.09–10.23 mg/L) and cypermethrin (3.41–11.78 mg/L) insecticides followed by neem essential oil (7.39–19.24 mg/L) and citrus extract (10.14–24.50 mg/L). However, LC₅₀ values were maximum in case of jaman plant extract (22.38–176.42 mg/L) followed by two herbicides, Logran (19.66–39.72 mg/L) and Topik (29.09–47.67 mg/L) However, LC₅₀ values were higher for topic herbicide (24.098 ppm) and jaman essential oil (16.383 ppm) after four days of treatment. Abamectin and cypermethrin insecticides, neem essential oil and citrus plant extract also killed adults of T. confusum quicker as compared other essential oils, extracts and herbicides. Results revealed that botanical formulations being environmentally safe could be used instead of highly hazardous pesticides for stored products’ pests. This study also elaborates the non-host toxicity of herbicides commonly applied in our agroecosystem.     

Efficacy of some medicinal plant extracts and essential oils against Colorado potato beetle,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae)

The Colorado potato beetle (CPB), Leptinotarsa decemlineata Say is one of the most important defoliator pests of potato in the world and it often causes extremely large potato yield losses. Potatoes are the preferred hosts for the pest, but it may feed and reproduce on a number of other plants in the Solanaceae family. Public concern related to pesticides and their residues in and on the foods had prompted a rise of consumer interest in organically produced foods. There have been growing efforts to detect and introduce suitable plant compounds that they have insecticidal properties. However, discovering of plant extracts for possible use in control of this pest requires more studying about plant extracts and compounds. Since resistance of CPB to common chemical insecticides is well documented and potato is one of the most prominent nutritious food products for many people in many countries, we examined the effect of essential oils (EOs) of European pennyroyal, lavander, mint, oregano and savory and methanolic extracts of fumitory, licorice and oregano on the pest. These plants were selected because they have medicinal properties and they are safe to human and environment. Adult CPBs were exposed to mentioned plant extracts and essential oils. LC₅₀ values for EOs of lavander and European pennyroyal were 4154 and 3561 ppm, respectively. The results demonstrated that essential oil of European pennyroyal (Mentha longifolia) would be suitable compound to control the pest, but essential oil of mint (Mentha spicata) was not effective against the pest. Also it is notable that at all treatments, the amount of adult feeding was very low.     

Screening of insecticidal activity of plant essential oils and extract-based formulations against four agricultural insect pests and their risk assessment

Frankliniella occidentalis (Pergande), Myzus persicae (Sulzer), Plutella xylostella (L), and Spodoptera exigua (Hübner) are notorious agricultural insect pests worldwide. Due to the rapid development of resistance to the conventional insecticides, the number of available insecticides might be reduced in a near future, and botanical insecticides can be considered as one of the potential candidates to solve this problem. In the present study, test formulations were prepared using plant essential oils and extracts as main active ingredients, and their insecticidal activity and phytotoxicity were examined. Among the combinations tested, two oil-in-water formulations of NRS-13 containing thyme white oil and NRS-24 containing basil and rosemary oils were selected based on their notable insecticidal activity and low phytotoxicity. Chemical analyses on the active essential oils, the quantitative analysis of the major components in the formulations, insecticidal activities under pot and field conditions, their acute toxicity on mammals, and ecotoxicity on fish were also examined. The NRS-13 (BaechooSafer^TM) and NRS-24 (JindiOut^TM) formulations showed species-specific insecticidal activity against P. xylostella and M. persicae, respectively. In addition, both formulations produced low acute oral and dermal toxicity, skin and eye irritation, and fish toxicities, which suggests those formulations based on essential oils could be considered as insecticides for pest control in small-scale environments in organic farming.     

Plant Essential Oils Synergize and Antagonize Toxicity of Different Conventional Insecticides against Myzus persicae (Hemiptera: Aphididae)

Plant-derived products can play an important role in pest management programs. Essential oils from Lavandula angustifolia (lavender) and Thymus vulgaris (thyme) and their main constituents, linalool and thymol, respectively, were evaluated for insecticidal activity and synergistic action in combination with insecticides against green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). The essential oils and their main constituents exerted similar insecticidal activity when aphids were exposed by direct sprays, but were non-toxic by exposure to treated leaf discs. In synergism experiments, the toxicity of imidacloprid was synergized 16- to 20-fold by L. angustifolia and T. vulgaris essential oils, but far less synergism occurred with linalool and thymol, indicating that secondary constituents of the oils were probably responsible for the observed synergism. In contrast to results with imidacloprid, the insecticidal activity of spirotetramat was antagonized by L. angustifolia and T. vulgaris essential oils, and linalool and thymol. Our results demonstrate the potential of plant essential oils as synergists of insecticides, but show that antagonistic action against certain insecticides may occur.     

Application of nanotechnology for the encapsulation of botanical insecticides for sustainable agriculture: Prospects and promises

This review article discusses the use of nanotechnology in combination with botanical insecticides in order to develop systems for pest control in agriculture. The main types of botanical insecticides are described, together with different carrier systems and their potential uses. The botanical insecticides include those based on active principles isolated from plant extracts, as well as essential oils derived from certain plants. The advantages offered by the systems are highlighted, together with the main technological challenges that must be resolved prior to future implementation of the systems for agricultural pest control. The use of botanical insecticides associated with nanotechnology offers considerable potential for increasing agricultural productivity, while at the same time reducing impacts on the environment and human health.     

Plant essential oils synergize various pyrethroid insecticides and antagonize malathion in Aedes aegypti

Pyrethroid resistance is a significant threat to agricultural, urban and public health pest control activities. Because economic incentives for the production of novel active ingredients for the control of public health pests are lacking, this field is particularly affected by the potential failure of pyrethroid‐based insecticides brought about by increasing pyrethroid resistance. As a result, innovative approaches are desperately needed to overcome insecticide resistance, particularly in mosquitoes that transmit deadly and debilitating pathogens. Numerous studies have demonstrated the potential of plant essential oils to enhance the efficacy of pyrethroids. The toxicity of pyrethroids combined with plant oils is significantly greater than the baseline toxicity of either oils or pyrethroids applied alone, which suggests there are synergistic interactions between components of these mixtures. The present study examined the potential of eight plant essential oils applied in one of two concentrations (1% and 5%) to enhance the toxicity of various pyrethroids (permethrin, natural pyrethrins, deltamethrin and β‐cyfluthrin). The various plant essential oils enhanced the pyrethroids to differing degrees. The levels of enhancement provided by combinations of plant essential oils and pyrethroids in comparison with pyrethroids alone were calculated and synergistic outcomes characterized. Numerous plant essential oils significantly synergized a variety of pyrethroids; type I pyrethroids were synergized to a greater degree than type II pyrethroids. Eight plant essential oils significantly enhanced 24‐h mortality rates provided by permethrin and six plant essential oils enhanced 24‐h mortality rates obtained with natural pyrethrins. By contrast, only three plant essential plants significantly enhanced the toxicity of deltamethrin and β‐cyfluthrin. Of the plant essential oils that enhanced the toxicity of these pyrethroids, some produced varying levels of synergism and antagonism. Geranium, patchouli and Texas cedarwood oils produced the highest levels of synergism, displaying co‐toxicity factors of > 100 in some combinations. To assess the levels of enhancement and synergism of other classes of insecticide, malathion was also applied in combination with the plant oils. Significant antagonism was provided by a majority of the plant essential oils applied in combination with this insecticide, which suggests that plant essential oils may act to inhibit the oxidative activation processes within exposed adult mosquitoes.     

Challenges to using neem (Azadirachta indica var. sianensis Valenton) in Thailand

The use of botanical insecticides based on the neem seed (Azadirachta indica var.siamensis Valeton) shows strong potential in the fight against important agricultural pests. Unfortunately, its use in rural Thailand is extremely limited. This study examines the efficacy of neem extracts processed under rural conditions; identifies factors that influence local farmers’ adoption of neem products; and proposes recommendations to promote the use of neem insecticides. The principal findings are: in field trials conducted under typical rural conditions, neem did not adequately control major pests of yard-long beans (Vigna sesquipedalis); and intensity of vegetable production, knowledge of neem insecticides and availability and accessibility of neem products strongly influence farmers’ adoption of neem products for pest control.     

植物次生代谢物质对蓟马的行为调控作用及其在蓟马防控中的应用

蓟马是多种农作物和园艺作物上的重要害虫,通过直接取食和间接传播病毒给作物造成巨大的经济损失。植物次生代谢物质在植物-昆虫互作中起到重要的作用,通过植物次生代谢物质调控害虫行为从而达到控制害虫的目的是一种害虫绿色防控的重要措施。本文综述了对蓟马类害虫具有引诱、驱避、抑制产卵、拒食、熏蒸毒性和毒杀作用的植物、植物提取物、植物精油和化合物,并讨论了植物次生代谢物质在蓟马防控中的应用潜能。对蓟马具有引诱作用的主要包括27科54种植物的挥发物或精油、29种苯环类、17种吡啶类和13萜烯类化合物,可开发为诱集植物和引诱剂;具有驱避作用的主要包括16科40种植物的挥发物或精油、20种萜烯类和6种苯环类化合物,可开发为驱避植物和驱避剂;具有抑制产卵、拒食、熏蒸毒性和毒杀作用的主要有20科42种植物的提取物或精油、6种生物碱类、15种萜烯类和5种苯环类化合物,可开发为植物源农药和熏蒸剂。本文最后讨论了应用植物次生代谢物质防控蓟马存在的作用效果不稳定、田间应用技术缺乏、作用机制不明确等问题,并展望了未来的研究方向,对基于植物次生代谢物质的蓟马绿色防控具有重要意义。     

拟除虫菊酯类杀虫剂对蜜蜂的毒性和影响

蜜蜂是最重要的农业授粉昆虫之一,蜜蜂在授粉过程中极有可能接触到广泛使用的广谱杀虫剂-拟除虫菊酯,大多数拟除虫菊酯对蜜蜂等农业授粉昆虫有较高的毒性.本文对拟除虫菊酯类杀虫剂的作用机理进行了综述;总结了蜂群及蜂产品中拟除虫菊酯类杀虫剂的残留现状、拟除虫菊酯对蜜蜂的急性毒性以及亚致死效应,讨论了拟除虫菊酯类杀虫剂复配农药对蜜...     

印度藏茴香植物精油对温室棉蚜的熏蒸毒性及其成分分析（英文）

【目的】棉蚜Aphis gossypii是世界各地室内和室外果树、蔬菜和观赏植物上最具危害性的害虫之一。这一害虫取食植物汁液,产生蜜露,传播植物病毒,对植物从质和量上产生破坏。为了控制温室中的这一害虫,植物精油可用作化学农药的替代药物。本实验研究了印度藏茴香Carum copticum植物精油对棉蚜成虫的熏蒸毒性。【方法】将研磨的印度藏茴香干种子用改良的挥发油提取器(Clevenger-type apparatus)进行水蒸馏。所有生物测定均在27±2℃,相对湿度65%±5%和光周期16L∶8D条件下进行。研究采用完全随机设计,6个处理(5个不同浓度的精油加对照)。每一浓度3次重复,每一重复20头成虫。【结果】结果表明,棉蚜成蚜接触印度藏茴香精油24 h后出现明显的死亡。该精油对棉蚜成蚜的致死中浓度(LC50)为1.21μL/L空气。棉蚜成蚜的死亡百分率对精油的施用表现出较高的敏感性。精油浓度为1.21μL/L空气时,估计的棉蚜的致死中时(LT50)为11.79 h。这一精油的熏蒸毒性与浓度和接触时间之间具有一定的相关性。GC/MS组分分析结果表明,该精油由18种化合物组成,最重要的是一些化合物引起了熏蒸毒性,如麝香草酚(占50.07%)、γ-萜品烯(占23.99%)和对异丙基苯甲烷(占22.90%)。【结论】本研究结果表明印度藏茴香植物精油对棉蚜具有较好的杀虫效果。印度藏茴香精油对棉蚜产生较大的影响,由于它具有较高的熏蒸毒性潜力,因此可在温室中用于这一害虫的综合治理。     

Effect of chemical complexity of essential oils on feeding deterrence in larvae of the cabbage looper

The relationship between chemical composition and feeding deterrent activity of seven essential oils is explored, including those from Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae), Cinnamomum zeylanicum Blume (Lauraceae), Lavendula latifolia (L.) Medicus, Lavendula angustifolia L., Mentha crispa L., Mentha arvensis L. and Mentha piperita L. (Lamiaceae) against an important agricultural pest, the cabbage looper (Trichoplusia ni Hübner, Noctuidae), using a leaf‐disc choice bioassay. Comparison of the deterrent activity of ‘full mixtures' with respective artificial blends missing individual constituents demonstrates that, for most oils, minor constituents in a mixture can be as important as major constituents with respect to the overall feeding deterrent effect. There is a lack of correlation between the feeding deterrent effect of an individual constituent of an essential oil and its contribution to the overall activity of the ‘full mixture’ in some cases. The effect of removing an individual constituent from the mixture of an essential oil depends on the unique properties of the mixture, which in turn may reflect the interaction of its constituents. Understanding the role and contribution of each constituent to the overall activity of the oil can facilitate the creation of artificial blends that optimize their efficacy against different pests.     

Economic Thresholds in Soybean-Integrated Pest Management: Old Concepts, Current Adoption, and Adequacy

Increasing global demands for food underline the need for higher crop yields. The relatively low costs of the most commonly used insecticides in combination with increasing soybean market prices led growers and technical advisors to debate the adequacy of recommended economic thresholds (ETs). The adoption of ETs and pest sampling has diminished in Brazil, leading to excessive pesticide use on soybean. The reduced efficacy of natural biological control, faster pest resurgence, and environment contamination are among the side-effects of pesticide abuse. To address these problems and maximize agricultural production, pest control programs must be guided by a proper integrated pest management (IPM) approach, including the ET concept. Therefore, the most appropriate time to initiate insecticide spraying in soybean is indicated by the available ETs which are supported by experiments over the last 40 years in different edapho-climatic conditions and regions with distinct soybean cultivars. Published scientific data indicate that preventive insecticide use is an expensive and harmful use of chemicals that increases the negative impact of pesticides in agroecosystems. However, the established ETs are for a limited number of species (key pests), and they only address the use of chemicals. There is a lack of information regarding secondary pests and other control strategies in addition to insecticides. It is clear then that much progress is still needed to improve ETs for pest management decisions. Nevertheless, using the current ETs provides a basis for reducing the use of chemicals in agriculture without reducing yields and overall production, thereby improving sustainability.     

Insect bacteria and hazelnut pests' biocontrol: the state of the art in Turkey.

Turkey is first among all hazelnut producing countries. However, it lags far behind them in terms of amount harvested per unit area. A main reason for this is that hazelnut has many agricultural pests that can not be effectively controlled. Chemical pesticides utilized to control these pests have hazardous effects on the environment. Increasing problems with resistance of these pests to most commonly used synthetic insecticides have spurred the search for alternative pest management strategies that would reduce reliance on synthetic insecticides. Biological control of hazelnut pests is an alternative control method to chemical pesticides. It is very important ecologically because of production of honey, milk and fish in the surrounding areas of hazelnut fields in Turkey. Several promising bacteriological studies have been made to find some biological control agents against these pests in Turkey. This paper presents a review of the current status of bacteriological studies on biological control of hazelnut pests in Turkey.     

Molecular cloning and characterization of a novel pyrethroid-hydrolyzing esterase originating from the Metagenome

Background  

Pyrethroids and pyrethrins are widely used insecticides. Extensive applications not only result in pest resistance to these insecticides, but also may lead to environmental issues and human exposure. Numerous studies have shown that very high exposure to pyrethroids might cause potential problems to man and aquatic organisms. Therefore, it is important to develop a rapid and efficient disposal process to eliminate or minimize contamination of surface water, groundwater and agricultural products by pyrethroid insecticides. Bioremediation is considered to be a reliable and cost-effective technique for pesticides abatement and a major factor determining the fate of pyrethroid pesticides in the environment, and suitable esterase is expected to be useful for potential application for detoxification of pyrethroid residues. Soil is a complex environment considered as one of the main reservoirs of microbial diversity on the planet. However, most of the microorganisms in nature are inaccessible as they are uncultivable in the laboratory. Metagenomic approaches provide a powerful tool for accessing novel valuable genetic resources (novel enzymes) and developing various biotechnological applications.     

Role of nanotechnology in agriculture with special reference to management of insect pests

Nanotechnology is a promising field of interdisciplinary research. It opens up a wide array of opportunities in various fields like medicine, pharmaceuticals, electronics and agriculture. The potential uses and benefits of nanotechnology are enormous. These include insect pests management through the formulations of nanomaterials-based pesticides and insecticides, enhancement of agricultural productivity using bio-conjugated nanoparticles (encapsulation) for slow release of nutrients and water, nanoparticle-mediated gene or DNA transfer in plants for the development of insect pest-resistant varieties and use of nanomaterials for preparation of different kind of biosensors, which would be useful in remote sensing devices required for precision farming. Traditional strategies like integrated pest management used in agriculture are insufficient, and application of chemical pesticides like DDT have adverse effects on animals and human beings apart from the decline in soil fertility. Therefore, nanotechnology would provide green and efficient alternatives for the management of insect pests in agriculture without harming the nature. This review is focused on traditional strategies used for the management of insect pests, limitations of use of chemical pesticides and potential of nanomaterials in insect pest management as modern approaches of nanotechnology.     

两种书虱微卫星富集文库的构建及比较

利用链霉亲和素与生物素之间的强亲和性原理,将链霉亲和素偶联的磁珠与微卫星探针(AC)12、(TC)12、(ATC)8、(ATG)8、(AAC)8、(ATAC)6及(GATA)6退火结合后,再亲和捕捉含接头和微卫星序列的单链书虱基因组DNA限制性酶切目的片段,经PCR扩增形成双链后进行克隆、建库。结果表明本研究成功构建了嗜卷书虱和嗜虫书虱共13个微卫星富集文库,包括6个嗜卷书虱文库,7个嗜虫书虱文库,其平均阳性克隆率为71.17%。经检测发现共得到两种书虱260个微卫星位点。这两种书虱微卫星富集文库的建立和高多态性微卫星位点的筛选将为嗜卷书虱和嗜虫书虱的种群遗传与进化、基因连锁图谱构建、分子系统发育研究等提供大量分子遗传标记,对其在实仓中的持续控制提供遗传学信息。     

Landscape simplification increases vineyard pest outbreaks and insecticide use

Diversifying agricultural landscapes may mitigate biodiversity declines and improve pest management. Yet landscapes are rarely managed to suppress pests, in part because researchers seldom measure key variables related to pest outbreaks and insecticides that drive management decisions. We used a 13‐year government database to analyse landscape effects on European grapevine moth (Lobesia botrana) outbreaks and insecticides across c. 400 Spanish vineyards. At harvest, we found pest outbreaks increased four‐fold in simplified, vineyard‐dominated landscapes compared to complex landscapes in which vineyards are surrounded by semi‐natural habitats. Similarly, insecticide applications doubled in vineyard‐dominated landscapes but declined in vineyards surrounded by shrubland. Importantly, pest population stochasticity would have masked these large effects if numbers of study sites and years were reduced to typical levels in landscape pest‐control studies. Our results suggest increasing landscape complexity may mitigate pest populations and insecticide applications. Habitat conservation represents an economically and environmentally sound approach for achieving sustainable grape production.     

Non-target impacts of forest defoliator management options: Decision for no spraying may have worse impacts on non-target Lepidoptera than Bacillus thuringiensis insecticides

Management programs for major forest defoliators such as gypsy moths or forest tent caterpillars, and crop pests such as the European corn borer have shifted from broad-spectrum insecticides to more environmentally benign microbial pesticides such as Bacillus thuringiensis (foliage sprays and transgenic toxin expression in plant tissues). Phytochemically resistant host plants and natural enemies have been used as alternative pest management strategies (including generalist tachinid flies such as Compsilura, viruses, microsporidians, and fungi), but all of these have some non-target impacts, as described from literature review. A sequence of lab and field studies were conducted to determine non-target impacts on native Lepidoptera in North America. The conclusions reached are that a decision not to spray Bt pesticides (i.e. to allow defoliation and natural pest outbreaks to run their course) could be as bad or worse for non-target Lepidoptera as the microbial insecticides would be. The important concept that must be maintained is that all pest management programs have some risk of negative non-target impacts, but it is the magnitude and relative importance that will remain the most critical issue for environmental impacts and pest management.