Host stage preference and parasitism behaviour of Aenasius bambawalei an encyrtid parasitoid of Phenacoccus solenopsis

In Pakistan, the cotton mealybug, Phenacoccus solenopsis Tinsley (Sternorrhyncha (Homoptera): Pseudococcidae), is a serious pest of many cultivated plants. A parasitoid, Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae), is associated with P. solenopsis. In order to mass rear A. bambawalei for a biological control programme, it is important to investigate the parasitoid’s host stage preference and its parasitism behaviour for P. solenopsis in order to optimise production. The present study showed that under both choice and no-choice conditions, the parasitoid preferred third instar and pre-reproductive host stage mealybugs for parasitism. Parasitoid larva developing inside the host exhibited a greater longevity, shorter developmental period and longer body size in these preferred host stages. Our study also confirmed that A. bambawalei showed no attraction to male mealybugs and no host feeding on any host stage was recorded. The ability of the parasitoid to effectively discriminate between suitable and non-suitable stages means that it is feasible to rear it on a mixed population.     

The potential distribution of an invasive mealybug Phenacoccus solenopsis and its threat to cotton in Asia

• 1 In recent years, an invasive mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) has attacked cotton (Gossypium hirsutum L.) in Pakistan and India, causing severe economic losses. This polyphagous pest was probably introduced accidentally from North America. Infestations have broken out suddenly and spread rapidly.
• 2 Seasonal and annual population growth data of P. solenopsis from nine locations in its native range in the U.S.A., and the distribution of the mealybug worldwide, were analyzed using the CLIMEX model. This indicated that tropical regions worldwide were highly suitable for P. solenopsis.
• 3 Its potential distribution was limited by cold in high latitudes and altitudes, and dryness in northern Africa, inland Australia and parts of the Middle East. CLIMEX was used to predict where P. solenopsis might establish, and to estimate the potential threat to cotton yield in Asia. The key limiting factors were low precipitation as well as minimum temperatures in northern areas.
• 4 When irrigation was factored into the simulation, the potential distribution of P. solenopsis expanded dramatically, indicating that P. solenopsis presents a great economic threat to cotton in Asia and other parts of the world.

     

Analysis of expressed sequence tags (ESTs) from a normalized cDNA library and isolation of EST simple sequence repeats from the invasive cotton mealybug Phenacoccus solenopsis

The cotton mealybug, Phenacoccus solenopsis Tinsley, is a serious and invasive pest. At present, genetic resources for studying P. solenopsis are limited, and this negatively affects genetic research on the organism and, consequently, translational work to improve management of this pest. In the present study, expressed sequence tags (ESTs) were analyzed from a normalized complementary DNA library of P. solenopsis. In addition, EST‐derived microsatellite loci (also known as simple sequence repeats or SSRs) were isolated and characterized. A total of 1107 high‐quality ESTs were acquired from the library. Clustering and assembly analysis resulted in 785 unigenes, which were classified functionally into 23 categories according to the Gene Ontology database. Seven EST‐based SSR markers were developed in this study and are expected to be useful in characterizing how this invasive species was introduced, as well as providing insights into its genetic microevolution.     

寄主植物对扶桑绵粉蚧体型及体内能源物质含量的影响

[目的]研究寄主植物对扶桑绵粉蚧雌成虫体型和体内能源物质含量的影响,为扶桑绵粉蚧的寄主适应性和风险分析提供科学参考.[方法]在室内用8种寄主植物连续饲养扶桑绵粉蚧5代后,测量7日龄雌成虫体长、体宽和体重,并测定体内能源物质(脂肪、可溶性蛋白质、可溶性糖)含量,分析上述指标在不同寄主间的差异.[结果]取食不同寄主后,扶桑...     

A review on biological interactions and management of the cotton bollworm,Helicoverpa armigera (Lepidoptera: Noctuidae)

Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is one of the most damaging insect pests globally, causing estimated global economic losses of over 3 billion US dollars annually. Crops most affected include cotton, tomato, soybean, grain crops such as corn and sorghum, chickpea and other pulses. Adults of this species possess strong migratory abilities (>2000 km), high fecundity and rapid reproductive rates; completing 4–6 generations per year in most cropping regions. Furthermore, the larvae are polyphagous, with a wide and diverse host range and possess the ability to enter diapause in order to survive adverse climatic conditions. At present, it is distributed across most of Oceania, Asia, Africa and southern Europe and has recently spread to South America. Various control measures have been trialled or proposed for the treatment of this pest, including synthetic insecticides, phytopesticides, microbial pesticides, macro-biocontrol agents (both parasitoids and predators) and the development of genetically modified crops (e.g. Bt cotton). Successful control necessitates the use of an integrated pest management (IPM) approach, wherein biological, chemical and physical control measures are combined for the greatest control efficacy.     

Insectivorous bats selectively source moths and eat mostly pest insects on dryland and irrigated cotton farms

Insectivorous bats are efficient predators of pest arthropods in agroecosystems. This pest control service has been estimated to be worth billions of dollars to agriculture globally. However, few studies have explicitly investigated the composition and abundance of dietary prey items consumed or assessed the ratio of pest and beneficial arthropods, making it difficult to evaluate the quality of the pest control service provided. In this study, we used metabarcoding to identify the prey items eaten by insectivorous bats over the cotton‐growing season in an intensive cropping region in northern New South Wales, Australia. We found that seven species of insectivorous bat (n = 58) consumed 728 prey species, 13 of which represented around 50% of total prey abundance consumed. Importantly, the identified prey items included major arthropod pests, comprising 65% of prey relative abundance and 13% of prey species recorded. Significant cotton pests such as Helicoverpa punctigera (Australian bollworm) and Achyra affinitalis (cotton webspinner) were detected in at least 76% of bat fecal samples, with Teleogryllus oceanicus (field crickets), Helicoverpa armigera (cotton bollworm), and Crocidosema plebejana (cotton tipworm) detected in 55% of bat fecal samples. Our results indicate that insectivorous bats are selective predators that exploit a narrow selection of preferred pest taxa and potentially play an important role in controlling lepidopteran pests on cotton farms. Our study provides crucial information for farmers to determine the service or disservice provided by insectivorous bats in relation to crops, for on‐farm decision making.     

杭州地区扶桑绵粉蚧危害调查及系统进化分析

【背景】扶桑绵粉蚧是近年来入侵我国的重要检疫性害虫,在我国多个省份均有发生,造成了严重的经济损失。【方法】于2009—2015年对杭州地区扶桑绵粉蚧的发生危害情况进行了实地调查,同时结合mt DNA COI分子标记方法,对扶桑绵粉蚧进行分子鉴定和系统进化分析。【结果】杭州市余杭区、萧山区和临安市3个地区发现扶桑绵粉蚧分布,共调查到寄主植物38科61属68种,以辣椒、茄子、番茄、南瓜、棉花、芝麻、菊花、苦荬菜、大花马齿苋和五色梅受害最严重。系统进化分析表明,杭州地区的扶桑绵粉蚧未发生明显的遗传分化,与我国其他地区扶桑绵粉蚧mt DNA COI基因相似度为99.4%~100%。【结论与意义】本研究为进一步研究扶桑绵粉蚧的遗传进化、可能的侵入途径以及科学防控提供了理论基础。     

Insecticidal control of the mealybug Phenacoccus gossypiphilous (Hemiptera: Pseudococcidae), a new pest of cotton in Pakistan

The mealybug Phenacoccus gossypiphilous (Stanley) played havoc with the cotton crop in Pakistan during 2005. To control this pest, insecticides of different groups were evaluated in both the laboratory and in field conditions. In the laboratory, bifenthrin, profenofos and chlorpyrifos proved to be the best insecticides for mealybug control, based on their susceptibility with the leaf dip method for their LC₅₀. In field conditions, the recommended application rates of methomyl, profenofos and chlorpyrifos provided the best control: the lethal time studies proved their efficiency for better and timely control of this sporadic pest. The present study has shown that the insecticides tested, in particular profenofos, chlorpyrifos, methomyl and bifenthrin, provide satisfactory control of the cotton mealybug. The control of the insect pest complex throughout the cotton crop predominantly depends on wise and justified use of these chemicals, and necessitates development of an integrated pest management strategy.     

广西及越南农业外来有害生物入侵现状

【背景】广西地理环境独特,与越南水陆相连,气候、作物等条件相似,边境贸易往来频繁,致使其成为我国遭受外来有害生物入侵最严重的地区之一。【方法】通过本底调查,分析总结了广西农业外来有害生物入侵的现状。【结果】广西主要入侵动物26种,入侵微生物18种,入侵植物21种,高风险入侵物种包括辣椒实蝇、木薯绵粉蚧、扶桑绵粉蚧、稻水象甲、黄瓜绿斑驳花叶病毒等;来自越南的潜在危险性有害生物共38种。【结论与意义】广西受外来有害生物入侵的风险加剧,并有进一步扩散蔓延的趋势。提出应对入侵生物的综合防控对策,为广西外来入侵有害生物的防控提供参考。     

Bt棉花害虫综合治理研究前沿

自1996年以来,全球Bt(Bacillus thuringiensis)棉花应用规模迅速增长,目前已占棉花种植总面积的60%左右,主要种植国家包括美国、澳大利亚、中国、印度和巴基斯坦等。大量研究表明,Bt棉花的大面积种植有效控制了多种靶标害虫的发生危害,从而大幅度减少了化学杀虫剂的使用量;化学杀虫剂的减少使用导致一些非靶标害虫的发生危害明显加重。针对Bt棉花生产中呈现出的害虫新问题,各国分别发展了由农业防治、生物防治、化学防治等不同措施构成的防控技术体系。     

An appetite for pests: Synanthropic insectivorous bats exploit cotton pest irruptions and consume various deleterious arthropods

Conservation biological control (CBC) seeks to minimize the deleterious effects of agricultural pests by enhancing the efficiency of natural enemies. Despite the documented potential of insectivorous bats to consume pests, many synanthropic bat species are still underappreciated as beneficial species. We investigated the diet of Kuhl's pipistrelle (Pipistrellus kuhlii), a common synanthropic insectivorous bat that forages in urban and agricultural areas, to determine whether it may function as a natural enemy in CBC. Faecal samples of P. kuhlii were collected throughout the cotton‐growing season from five roost sites near cotton fields located in a Mediterranean agroecosystem, Israel, and analyzed using DNA metabarcoding. Additionally, data on estimated abundance of major cotton pests were collected. We found that the diet of P. kuhlii significantly varied according to sites and dates and comprised 27 species of agricultural pests that were found in 77.2% of the samples, including pests of key economic concern. The dominant prey was the widespread cotton pest, the pink bollworm, Pectinophora gossypiella, found in 31% of the samples and in all the roosts. Pink bollworm abundance was positively correlated with its occurrence in the bat diet. Furthermore, the bats’ dietary breadth narrowed, while temporal dietary overlap increased, in relation to increasing frequencies of pink bollworms in the diet. This suggests that P. kuhlii exploits pink bollworm irruptions by opportunistic feeding. We suggest that synanthropic bats provide important pest suppression services, may function as CBC agents of cotton pests and potentially contribute to suppress additional deleterious arthropods found in their diet in high frequencies.     

Biological activity of Pakistani isolate SpltNPV-Pak-BNG in second,third and fourth instar larvae of the leafworm Spodoptera litura

Recently, a novel isolate of the baculovirus Spodoptera litura nucleopolyhedrovirus (SpltNPV) has been isolated from Pakistan, which is distinct from the type species SpltNPV-G2 (ICTV). Here, we examined the biological activity of this isolate (SpltNPV-Pak-BNG) in second (L2), third (L3) and fourth instar (L4) larvae of the leafworm S. litura, more specifically to measure biological properties that are relevant for use of this virus for pest control under field conditions. The median lethal dose for L2 and L3 instar larvae was similar, but significantly lower than for L4 larvae. Likewise, the survival time was similar for L2 and L3 larvae (84?h), but was significantly longer for L4 instar larvae (108?h). Thus, in terms of efficacy, S. litura L2 and L3 instar larvae are the preferred targets for S. litura control with SpltNPV-Pak-BNG in field crops in Pakistan. On the basis of our data spray regimes can be designed to control the leafworm in cotton and vegetable crops targeting L2 and L3 larvae.     

盐碱旱地转Bt基因抗虫棉田主要害虫及其天敌种群消长动态

【目的】近年来,我国长江流域和黄河流域棉花面积锐减,种植区域向滨海盐碱地或干旱地转移。研究盐碱旱地转基因棉田与非转基因棉田昆虫群落差异,可为盐碱旱地对转基因棉田生物影响和盐碱旱地转基因棉田害虫防治提供理论指导。【方法】在山东东营和河北枣强盐碱干旱地转Bt基因棉田分别设置常规施药田和非施药田,进行了系统的田间昆虫种群消长动态的调查和统计分析。【结果】中轻度盐碱旱地种植转基因棉花对靶标害虫棉铃虫具有较好的控制作用;与非转基因棉花相比,对其他非靶标害虫棉蚜、烟粉虱和盲蝽及自然天敌龟纹瓢虫、草间小黑蛛种群数量无显著影响,草蛉种群数量在转基因棉田低于非转基因棉田;喷施化学农药对棉铃虫幼虫和棉蚜的防治作用较好,对烟粉虱和盲蝽的防治效果年度间和试验点间有差异,对龟纹瓢虫的杀伤力较大,对草间小黑蛛和草蛉未见明显影响。【结论】盐碱旱地对棉田不同的害虫和天敌影响不同,且转基因棉田与非转基因棉田昆虫群落结构与对照棉田无显著差异。     

Transgenic cotton expressing CYP392A4 double‐stranded RNA decreases the reproductive ability of Tetranychus cinnabarinus

As a polyphagous pest, Tetranychus cinnabarinus has the ability to overcome the defense of various hosts, and causes severe losses to various economically important crops. Since the interaction between pest and host plants is a valuable clue to investigate potential ways for pest management, we intend to identify the key genes of T. cinnabarinus for its adaption on cotton, then, with RNA interference (RNAi) and transgenic technology, construct a transgenic cotton strain to interfere with this process, and evaluate the effect of this method on the management of the mites. The difference of gene expression of T. cinnabarinus was analyzed when it was transferred to a new host (from cowpea to cotton) through high‐throughput sequencing, and a number of differentially expressed genes involved in detoxification, digestion and specific processes during the development were classified. From them, a P450 gene CYP392A4 with high abundance and prominent over‐expression on the cotton was selected as a candidate. With transgenic technology, cotton plants expressing double‐stranded RNA of CYP392A4 were constructed. Feeding experiments showed that it can decrease the expression of the target gene, result in the reduction of reproductive ability of the mites, and the population of T. cinnabarinus showed an apparent fitness cost on the transgenic cotton. These results provide a new approach to restrict the development of mite population on the host. It is also a useful attempt to control piercing sucking pests through RNAi and transgenic technology.     

Microbial control of cotton pests: use of the naturally occurring entomopathogenic fungus Aspergillus sp. (BC 639) in the management of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) and beneficial insects on transgenic cotton crops

The commercial adoption of transgenic Bacillus thuringiensis (Bt) cotton (Bollgard II®) reduced the use of insecticides to control Helicoverpa spp. However, the ineffectiveness of the Bt toxin against sucking pests such as silverleaf whiteflies (Bemisia tabaci) resulted in a marked increase in B. tabaci populations and in the use of insecticides to control this pest. The effect of the entomopathogenic fungus Aspergillus sp. BC 639 on B. tabaci and beneficial insects (predominantly predatory insects) was studied in commercial cotton field trials. The results showed that oil-based extracts of the entomopathogenic fungus BC 639 control the number of B. tabaci adults and nymphs in commercial transgenic cotton crops. The BC 639 fungus caused 60.0%, 67.2%, and 68.8% mortality in adults, and 54.6%, 62.3%, and 51.7% in nymphs at 7, 14, and 21 days after treatment, respectively, relative to the unsprayed controls. The effect of BC 639 at concentrations of 125, 250, and 500?ml/ha on low-density B. tabaci (～10 nymphs/leaf) did not differ significantly from that of the commercial insecticide (pyriproxifen). However, at higher densities (>50 nymphs per leaf), low concentrations of BC 639 (125 and 250?ml/ha) were not as effective as 500?ml/ha BC 639 in successfully controlling the pest. A simple graphic analysis suggested that the more B. tabaci nymphs per leaf, the fewer adults per leaf, and that once the number of nymphs increased to ～70 per leaf, a negative feedback regulatory effect reduced the survivorship of the nymphs and adults and/or caused the emigration of the adults from the contaminated leaves in search of new resources. Therefore, the ability of BC 639 to control B. tabaci adults and nymphs with minimal effects on predatory insects indicates its potential utility in supplementing integrated pest management programmes for cotton crops.     

云南扶桑绵粉蚧的发生及防治

扶桑绵粉蚧是一种全球恶性入侵害虫,2008年传入我国,目前已有13个省区报道其为害,2009年在云南省被发现,截至2013年3月,云南省共8个州(市) 10个县(市)已有分布。扶桑绵粉蚧寄主范围广,危害性大,适应性强。同时,云南省花卉、蔬菜调运及进出口贸易频繁,加之气候类型丰富、水热条件优越、自然地理环境复杂多样、动植物资源丰富等优势,有利于扶桑绵粉蚧的入侵、定殖与扩散,易造成较大的经济损失。目前,关于云南省扶桑绵粉蚧的研究仍然缺乏,现就扶桑绵粉蚧在云南的发生现状、潜在风险和防治措施等方面进行概述,以期为该虫的有效防范提供参考。     

基于宏基因组测序的扶桑绵粉蚧内共生菌多样性研究

[目的] 扶桑绵粉蚧是一种重要的入侵害虫,也被列为我国的检疫性有害生物。内共生菌的群落结构及与扶桑绵粉蚧关系的研究,将为研究扶桑绵粉蚧的入侵生物学和防治提供新的思路和参考。[方法] 利用宏基因组测序技术对室内饲养扶桑绵粉蚧内共生菌的物种组成、丰度和多样性进行了研究。[结果] 共鉴定获得29个门,47个纲,105个目,178个科,245个属,299个种。变形菌门、γ-变形菌纲、肠杆菌目、肠杆菌科、伯克氏菌属、Candidatus分别为各分类阶元的优势种群。共预测了36505个基因,其中77.27%的基因分布在200~499 nt的范围内。基因集KEGG注释表明,扶桑绵粉蚧内共生菌代谢相关基因最多,达384个,占49.48%;环境信息处理基因最少,仅8个,占1.03%;代谢相关基因最多的为氨基酸代谢基因,为64个,占28.19%。基因集COG注释表明,翻译、核糖体结构和生物发生的基因最多,其次为氨基酸转运和代谢基因,分别占27.64%和12.31%。[结论] 初步确定了扶桑绵粉蚧内共生菌菌群的群落结构和优势菌群,并初步分析了这些内共生菌的功能基因情况,为进一步研究内共生菌与扶桑绵粉蚧之间的关系提供了基础,以期从内共生菌的角度为该虫的防控提供新的策略。     

In search of artificial domatia for predatory mites

Banker plants can enhance biological pest control by providing both floral resources and appropriate oviposition sites, e.g. through acarodomatia, to predator species. The use of materials mimicking domatia i.e. artificial domatia may be an economically favourable alternative to the use of banker plants bearing domatia. The aim of the present study was to identify materials that are able to host eggs of the Neoseiulus californicus predatory mite but not those of the Tetranychus urticae pest mite. In a laboratory experiment, the oviposition of predatory and phytophagous mites were compared in Petri dishes containing leaves. The different modalities compared were (i) natural domatia of Viburnum tinus or (ii) one of twelve potential artificial domatia materials. The overall oviposition response of predatory mites to all artificial domatia was similar to that of the natural domatia. The oviposition of the Tetranychus urticae pest mite did not increase in response to the artificial domatia. Five artificial domatia hosted as many eggs of the predatory mite as observed in the natural domatia. The effect of the physical properties of artificial domatia was also tested and N. californicus was found to favour the artificial domatia that had high heat retention capacities for oviposition. Three of these artificial domatia were tested on rose plants in a greenhouse experiment; none of which enhanced the biological control on the plants under these conditions. The present study highlights the difficulty in identifying and using suitable artificial domatia as substitutes to banker plants in biological pest control efforts.