Laboratory evaluation of toxicity of selected insecticides against egg and larval stages of cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

Background The cryptic nature of pink bollworm Pectinophora gossypiella(Saunders)larvae enables its reduced vul-nerability to insecticidal control.Further,the development of resistance against Bacillus thuringiensis(Bt)toxins posed a serious threat to transgenic cotton cultivation.This necessitated determining the critical timing of spray applications on the control effectiveness.This study assessed the influence of egg age(freshly laid vs.three-day-old)and the loca-tion of larvae(directly exposed to the insecticide residues on the boll rind vs.burrowed inside the bolls)on insecticide control efficacy.Results The results revealed a significant decrease in the ovicidal activity of tested insecticides with an increase in the age of eggs from one day old to three days old(paired t-test,P<0.05).The larvae directly exposed to the insec-ticide residues on the boll rind were more susceptible(>80%mortality)than the larvae exposed after they had bur-rowed inside the bolls(<49%mortality).The inhibitory effects of tested insecticides on developmental biology were more pronounced in the experiment on pre-larval release insecticide treatment compared with insecticide treatment given post-larval release and entry inside the bolls.Conclusion Egg age influences the insecticide susceptibility,as does the larval location,directly exposed vs bur-rowed inside the bolls.Older eggs and the larvae that had burrowed inside the green bolls of cotton were relatively less susceptible to the insecticide treatments.The toxic effects of insecticides on egg and larval stages were primar-ily ephemeral.These findings are significant for devising a comprehensive strategy for pink bollworm management on a sustainable basis.

Performances of the cotton bollworm,Heliothis armigera (Hubner) at different temperatures and relative humidities

The cotton bollworm, Heliothis armigera (Hubner) is an important insect species at-tacking many crops. Their performances have been examined at temperatures from 15℃ to 35℃ and relative humidities (RH) between 22.5% and 100%, respectively, in order to assess possible effect of climate in future on its occurrence and infestation. Durations of all developmental stages of the insect shortened with increasing temperature. The temperature favoring population growth ranged from 25℃ to 30℃.Larval duration and adult longevity decreased as relative humidity increased, but development of other stages was independent of RH. At RH of over 64%, their survival rate, egg production and oviposition rate varied a little, and all the population parameters of the insect remained at a relative constant level.

Combining Ability and Heterosis Between High Strength Lines and Transgenic Bt (Bacillus thuringiensis) Bollworm-Resistant Lines in Upland Cotton (Gossypium hirsutum L.)

To analyse the combining ability and heterosis between high-strength lines and transgenic Bt bollworm-resistant lines in upland cotton, 5 high-strength lines were crossed as female lines with 12 transgenic Bt bollworm-resistant lines according to NCII design. It was demonstrated that the compositions of variance in various traits were quite different. For seed cotton yield, lint yield, boll numbers per plant and boll weight, the dominant (special combining ability) effects were the major effects, accounting for 87.38, 84. 40, 80. 04 and 64. 46% of the total phenotypic variances, respectively, while for fibre strength and micronaire value, the additive (general combining ability) effects had the major effects, with a ratio of additive variance to phenotypic variance of 78.85 and 43.80%. As for lint percent and 2.5% span length, the dominant and additive variances had similar effects, in phenotypic variances (54.94 and 40.11% for lint percent, 45.76 and 42.49% for 2. 5% span length, respectively). The mid-parent heterosis (Hpm), surpassing parent heterosis (Hpb) and competitive heterosis (Hck) for seed cotton yield and lint yield were both extremely significant. For fibre properties, the Hck and Hpm of 2.5 % fibre span length were extremely significant, the Hck of fibre strength was significant, and the favorable negative Hck of micronaire was also extremely significant. The increments of hybrid over common variety were 17% for lint yield and fibre strength, 7% for fibre span length, and 4 % for fineness.

Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North China

Background： The cotton bollworm （Helicoverpa armigera） is one of cotton＇s most destructive insect pests in terms of yield and quality. Since 1997, China has grown commercially available transgenic Bacillus thuringiensis （Bt） cotton. We aimed to investigate the variation in resistance of transgenic Bt cotton varieties to cotton bollworm in North China. Methods： Populations of cotton bollworm were monitored from 2008 to 2015 in environments where Bt cotton was planted adjacent to other non Bt crops. The study included 197 Bt cotton varieties planted in 42 counties/locations in three provinces （Hebei, Shandong and Henan） of North China, which were evaluated through field investigations, bioassays, and enzyme linked immunosorbent assays （ELISA）. Results： The average number of cotton bollworms never exceeded the action threshold （10 larvae per 100 cotton plants）, however, their number reached 19.55 per 100 cotton plants in 2011. The ratios of damaged plants to total Bt cotton stem tips, buds, and bolls was low except in 2010, when the ratios reached 1.82%, 2.09%, and 10.63%, respectively. The results of bioassay showed that the corrected mortality were higher at the second generation cotton bollworm stage than the third and fourth germination stages. Totally, Bt protein content declined sharply at the seedling stage from 2008 to 2015. Conclusions： This study indicated that almost all Bt cotton varieties were capable to effectively control the populations of cotton bollworm in North China.

Does cotton bollworm show cross-resistance to the Bacillus thuringiensis toxins Cry1Ac and Cry2Ab? A mini review

Since 1996, transgenic Bacillus thuringiensis(Bt) cotton has been commercially grown in numerous countries in an effort to stem the losses caused by key lepidopteran pests. However, the development of pest resistance to Bt toxins has jeopardized the continued utilization of Bt cotton. As a strategy designed to circumvent the development of resistance, Bt cotton varieties expressing two or more toxins targeting the same pest have been introduced. Nevertheless, from the perspective of long-term planting of Bt cotton, the potential risk of cross-resistance to these Bt toxins is a threat that cannot be ignored. In this paper, we review current research(including that based on the analysis of protein binding sites and resistance genes) on the resistance of cotton bollworm(Helicoverpa armigera) to the Bt toxins Cry1 Ac and Cry2 Ab and the interrelationship between these toxins. On the basis of existing evidence, we assume that the actions of Cry1 Ac and Cry2 Ab against cotton bollworm are not completely independent, and then propose the "resistance-associated gene mutation potential hypothesis". Although the mechanisms underlying the resistance of pests to Bt toxins are yet to be comprehensively elucidated, this hypothesis could undoubtedly have important implications for adopting "pyramid" strategy in the future. Further research is recommended to devise strategies to retard the development of H. armigera resistance to Bt cotton, either using different Bt toxins or their various combinations.

Management of cotton bollworms Helicoverpa armigera and Earias vittella by ento mopathogenic nematodes

Background: The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic cotton necessitates the exploration of an alternate strategy to manage bollworms. The entomopathogenic nematodes(EPN) Steinernema carpocapsae strain APKS2 and Heterorhabditis bacteriophora strains KKMH1 and TRYH1 at different concentrations of 1 × 10^(9) infective juveniles(IJs)·hm^(-2), 2 × 10^(9)IJs.hm^(-2), and 3×10^(9)IJs·hm^(-2) in 500 L of water were evaluated as a foliar spray in fields naturally infested with H.armigera and F.vittella located at Eastern Block and and Cotton Research Farm of Tamil Nadu Agricultural University, Coimbaotre, India during October 2010–February 2011 and October 2011–February 2012, respectively.Results: In general, all three tested EPN strains reduced the larval population of H. armigera and E. vittella;reduced square and boll damage;and subsequently increased cotton yield compared with the untreated control. The S. carpocapsae APKS2 is most e ective against H. armigera whereas both S. carpocapsae APKS2 and H. bacteriophora KKMH1 were equally effective against E. vittella. The higher dose of 3×10^(9)IJs·hm^(-2) was highly significant in the reduction of H. armigera larvae. However, the doses 2×10^(9)IJs·hm^(-2)and 3×10^(9)IJs·hm^(-2) were equally effective for E. vittella control. The S. carpocapsae APKS2 at 3×10^(9)IJs·hm^(-2) caused a 62.2% reduction of H. armigera larvae, 34% reduction of square damage, 58.5% reduction of boll damage, and yielded 45.5% more seed cotton than the untreated control plots. In E. vittella infested field, S. carpocapsae strain APKS2 and H. bacteriophora strain KKMH1 at 2×10^(9)IJs·hm^(-2)resulted in 60.6%~62.4% larva reduction, 68.4%~70.7% square damage reduction, 66.6%~69.9% boll damage reduction and 45.9% yield increase over the untreated control. The effective EPN treatments were comparable to the chemical insecticide chlorpyriphos 20% emulsifiable concentrate spraying at 2 mL·L^(-1).Conclusions: This study has shown that EPN have great potential in the management of the bollworm complex in cotton. Foliar spraying EPN strain S. carpocapsae(APKS2) at 3×10^(9)IJs·hm^(-2) and S. carpocapsae(APKS2) or H. bacteriophora(KKMH1) at 2×10^(9)IJs·hm^(-2) five times at 10days intervals are the best for the management of H. armigera and E. vittella, respectively.

THE FUNDAMENTAL STRATEGY FOR THE CONTROL OF COTTON BOLLWORM OUTBREAKS IN CHINA

on the basis of the analysis of the factors causing the cotton bollworm outbreaks and control failure, the authors recommend that the fundamental strategy for solving the problem of cotton bollworms in China should be to conduct area-wide unified controls rather than depend on insecticides. The unified control system is the guarantee for Integrated Pest Management (IPM) for small-scale crop owners at present. So the authors call on policymakers to put stress on organizing individual growers to carry out area wide unified controls.

棉铃虫发生发展与气候条件的关系研究进展

棉铃虫(Helicoverpa armigera)属鳞翅目夜蛾科,是一种世界性的害虫,在世界各地均有分布。因其具有远距离迁飞,繁殖力强等特点,条件适宜时常大面积暴发成灾,给农业生产带来较大损失。摸清棉铃虫生活习性、种群变化规律是棉铃虫防治的前提条件。由于棉铃虫是变温昆虫,气候条件对其生长发育、成灾机制等产生极大影响。因此,本文系统综述了气候变暖对棉铃虫影响的研究进展,包括棉铃虫生长发育、体色变化、繁殖、滞育、飞行、越冬、与作物的互作关系等方面,并对未来研究重点进行了展望。

Expression of two insect-resistant genes cryIA (b&c)/GNA in transgenic tobacco plants results in added protection against both cotton bollworm and aphids

The synthesized Bacillus thuringiensis insecticidal protein gene crylA(b&c) and the synthesized gene GNA, (the mannose specific lectin from snowdrop ( Galanthus nivalis)), tumefaciens have been inserted into plant expression vector pGW4BAI. Leave stripes of Nico-tiana tabacum var. K326 have been transformed with Agrobacterium tumefaciens strain LBA4404 harboring the plant expression vector. 28 kanamycin resistant tobacco plants

Determining the major Bt refuge crops for cotton bollworm in North China

Evaluation of the effectiveness of refuge strategies involved in cotton boll- worm Bt resistance management would be aided by technologies that allow monitoring and quantification of key factors that affect the process under field conditions. We hy- pothesized that characterization of stable carbon and nitrogen isotopes in adult bollworm, Helicoverpa armigera （Htibner） （Lepidoptera： Noctuidae） moths may aid in determining the larval host that they developed upon. We found moths reared from larvae fed on peanut, soybean or cotton, respectively, could be differentiated using isotopic analyses that also corresponded to their respective larval host origins. These techniques were then used to classify feral second-generation bollworm moths caught in Bt cotton （Gossypium hirsu- rum） fields into different populations based on their isotopic signatures. In 2006-2007 feral moths captured in Bt cotton fields predominantly correlated with the peanut （Arachis hypogea） having served as their larval host, indicating this is the most important refuge crop for Bt-susceptible bollworm individuals （providing 58%-64% individuals） during independent moth peaks for the second generation in North China. The remaining feral moths correlated with soybean （Glycine max） （0-10%）; other C3 plant （20%-22%） and non-C3 plant （12%-14%） host types also provided some Bt-sensitive moths. Field obser- vations showed that peanut constitutes the primary refuge crop contributing to sustaining Bt-susceptible moths dispersing into cotton in North China. These results suggest that peanut may be a more effective refuge to sustain Bt-susceptible bollworm individuals and reduce the risk of development of a Bt-resistant biotype.

Transgenic tobacco plants expressing synthetic Cry1Ac and Cry1Ie genes are more toxic to cotton bollworm than those containing one gene

Transgenic tobacco plants carrying Cry1Ac, Cry1Ie or both genes were obtained. In the leaves of transgenic plants carrying both genes, the contents of Cry1Ac and Cry1Ie proteins were 0.173% and 0.131% of the total proteins, respectively. Cry1Ac protein content was 0.182% and Cry1Ie protein con- tent was 0.124% of the total proteins in the leaves of transgenic plants containing only one Bt gene. Fresh leaves of transgenic tobacco and wild-type plants were used for the insect bioassay against wild-type and Cry1Ac-resistant cotton bollworm (Helicoverpa armigera). The bioassay results showed that transgenic plants carrying both genes were significantly more toxic to wild-type and Cry1Ac-resistant cotton bollworm than those carrying Cry1Ac or Cry1Ie alone. This study indicates that the higher toxicity of transgenic tobacco plants carrying both genes is caused by the cooperative function of both Bt proteins, thus providing a potential way to delay the development of insect resis- tance to transgenic crops.

棉铃虫室内继代饲养常见问题及对策

棉铃虫是一种危害较大的农业害虫,同时也是教学和科研中常用的实验昆虫。人工饲养过程中常因管理操作不当,使种群难以为继。本文根据多年实验室饲养棉铃虫经验,分析了继代饲养过程中常出现的问题及对策,以期为棉铃虫室内继代饲养提供参考。

河西地区玉米田棉铃虫对2种Bt蛋白的敏感性监测

【目的】明确河西走廊棉铃虫对玉米Bt蛋白的敏感性,为科学监测棉铃虫的发生危害规律提供科学依据。【方法】饲料表面覆盖毒素法测定了河西走廊嘉峪关(JYG)、酒泉(JQ)、张掖(ZY)、武威(WW)4个棉铃虫地理种群对Cry1Ab和Cry1Ac蛋白的敏感性,计算LC_(50)和LC_(99).【结果】JYG、JQ、ZY和WW种群对Cry1Ab的LC_(50)分别为0.1162、0.1460、0.1721、0.2004μg/cm^(2),LC_(99)分别为7.2778、6.0807、97.0666和27.1037μg/cm^(2);JYG、JQ、ZY和WW地理种群对Cry1Ac的LC_(50)分别为0.1050、0.2554、0.0172和0.0456μg/cm^(2),LC_(99)分别为0.1598、11.7953、1.1904、7.4709μg/cm^(2),其中JQ地理种群对Cry1Ac的LC_(50)值显著高于其他地理种群.【结论】河西走廊玉米棉铃虫对Cry1Ab和Cry1Ac蛋白的敏感性较高,暂未对Cry1Ab和Cry1Ac蛋白产生抗性。但应该持续加强监测,以避免Bt交互抗性产生应用风险.

棉花无蜜腺性状抗棉铃虫及红铃虫效果研究

棉花无蜜腺性状抗棉铃虫及红铃虫效果研究郑冬官，方其英（安徽农业大学合肥２３００３３６）郑厚今（安徽省农业厅，合肥２３０００１）Ｒｅｓｉｓｔａｎｃｅｏｆｃｏｔｔｏｎｎｅｃｔａｒｉｌｅｓｓｃｈａｒａｃｔｅｒｔｏｂｏｌｌｗｏｒｍａｎｄｐｉｎｋｂｏｌｌｗｏｒ...

玉米田四代棉铃虫老熟幼虫空间分布型及应用(英文)

[ Objective] The paper was to study the spatial distribution pattern of fourth-generation mature larvae of cotton bellworm in corn field. [ Method] The plots with different occurrence densities of fourth-generation cotton bollworm were investigated from August to September in 2009. Six groups of sampling data were obtained, and seven indicators including aggregation index method, Iwao method and Taylor method, etc. were used to determine its spatial distribution pattern. [ Result ] Aggregation index test showed that in all plots, Moore I 〈 0, Lloyed m＊/m 〈 1, Kuno Ca 〈 0, diffusion coefficient C 〈 1, diffusion index 16 〈 1, negative binomial distribution K 〈 0, indicating that mature larvae of cotton bollworm showed uniform distribution in summer corn. Iwae regression equation of fourth-genera- tion mature larvae of cotton boUworm in summer corn was m ＊ = 0. 090 6 ＋ 0. 766 9 m, r = 0. 986 3, indicating that the basic components of cotton bollworm distribu- ted was single individual, and mature larvae of cotton bollworm in summer corn showed uniform distribution. The optimal sampling number of fourth-generation ma- ture larvae of cotton bollworm in corn under different population densities could be calculated using formula N1 = （ 1. 090 6/m -0. 233 1 ）/D2. [ Conclusion] The result provided basis for accurate evaluation of population quantities and variation law of cotton boUworm, as well as prediction and control of the pest.

陆地棉高强纤维品系和Bt基因抗虫棉的配合力与杂种优势研究

采用NCⅡ设计 ,以 5个高强纤维品系为母本 ,12个Bt基因抗虫棉品系为父本配制杂交组合 ,分析了高强纤维品系与Bt基因抗虫棉品系杂交组合性状的配合力效应和杂种优势表现。结果表明 ,籽、皮棉产量、单株铃数和铃重具极显著的特殊配合力 (显性 )方差 ,衣分的一般配合力 (加性 )和特殊配合力方差均极显著 ,纤维品质2 .5 %跨长、比强度和麦克隆值具极显著的一般配合力方差。产量构成因素的优势单株铃数 >铃重 >衣分 ;纤维品质性状的群体平均优势 2 .5 %跨长 >麦克隆值 >比强度 ,竞争优势比强度 >2 .5 %跨长 >麦克隆值。利用高强纤维品系与Bt基因抗虫棉品系配制的杂交组合 ,F1代皮棉产量较现有推广品种增产 17.0 %以上 ,纤维比强度提高 ,长度增加 7.0 %以上 ,细度提高 4 .0 %以上。

转基因抗虫棉的抗性鉴定

１９９４～１９９５年采用棉铃虫初孵幼虫鉴定Ｒ１、Ｒ２、Ｒ３代Ｂｔ转基因棉花２０００多株次，筛选出Ｒ１代抗虫效果达８０％以上的单株１１个，占参测株６．２１％；Ｒ２代（株系）１５个，占参测株系１３．８９％；Ｒ３代３７５株，占参测株７１．２９％。１２份材料进入复鉴，８份材料在罩笼接虫中，百株活虫数及被害蕾铃率平均比对照分别减少８８％～１００％及９０％～１００％；叶、蕾饲喂棉铃虫３龄幼虫，毒性效果均在８０％以上，３龄棉铃虫幼虫取食抗虫棉后，取食量、排泄量及体长和体重增长率比对照减少５０％～１０７％，第四天出现死虫，且对红铃虫亦有较强的抗性。

转基因棉Bt毒性表达的时空动态及对棉铃虫生存、繁殖的影响

转Ｂｔ基因棉３１０品系在不同发育阶段，对棉铃虫的毒性表达测定表明，（１）棉株各空间组织在不同发育阶段均能强力阻止棉铃虫取食，表达出较高的抗虫效果。（２）棉株不同空间组织在同一时期，毒性表达存在差异，以营养组织，中、小蕾高于大蕾和铃。（３）同一组织毒性表达随着棉株生长、发育、成熟、衰老逐渐呈动态下降。（４）前后各阶段，同一组织饲喂棉铃虫，死亡所需要天数呈动态增加，但最终生存率降低到一个较低水平。存活老熟幼虫重量、蛹重及蛹羽化率比对照棉铃虫下降３０％～５０％，羽化的蛾子进行自交或异交均能产下受精率、孵化率很高的卵。取食Ｂｔ转基因棉的雌蛾产卵量比对照减少５０％～７０％。

棉铃虫灾害的长期性及性信息素的减灾控害作用

简要分析了我国棉铃虫灾害的长期性，并较全面地介绍了性信息素在减灾控害中的作用．这些作 用可分为：帮助识别对象害虫、监测种群动态、迅速普及虫情信息。直接诱杀雄虫以及提前１周开展减灾 行动等。直接诱杀雄虫后，引起雌雄比上升，雌蛾产卵量下降，孵化率降低，幼虫及为害量减少，其中 幼虫量一般减少２０％～５０％。根据在新疆、山东等地的试用经验，作者首次指出性信息素帮助识别害 虫和迅速普及虫情信息对减灾的关键作用，并讨论了性信息素的干扰交配和诱杀雌虫的可能作用，以及 使用性信息素与农业可持续发展的关系．

烟青虫和棉铃虫在烟草上的生态位及其种间竞争

通过 2 0 0 0～ 2 0 0 1两年的田间调查和室内饲养 ,测定了烟青虫和棉铃虫在烟草上的生态位和种间竞争系数。结果表明 :棉铃虫在烟草上的时间生态位宽度、生态位重叠均大于烟青虫 ,两者的时间生态位相似性比例为 0 .7342 ;两种害虫的空间生态位宽度、生态位重叠很相近 ,生态位相似性比例高达 0 .85 5 9。烟青虫的竞争系数为 0 .312 2 ,棉铃虫的竞争系数为 1.832 0 ,说明棉铃虫的竞争力大于烟青虫。在烟株同一部位两种害种共存率最高仅有 9.30 %。