Conserving the efficacy of insecticides against Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  The diamondback moth (DBM), Plutella xylostella (L.) (Lep., Plutellidae), is one of the most destructive insect pests of crucifers worldwide. It was the first crop insect reported to be resistant to DDT and now in many crucifer-producing regions it has shown significant resistance to almost every insecticide applied in field including biopesticides such as crystal toxins from Bacillus thuringiensis and spinosyns from Saccharopolyspora spinosa . In certain parts of the world, economical production of crucifers has become almost impossible because of its resistance to insecticides and resulting control failure. A coordinated resistance management program needs to be implemented with the involvement of pesticide industry, local pesticide regulatory authorities, scientists and farmers. The judicious use of chemicals in conjunction with other control measures (e.g. biological control agents, resistant varieties, proper fertilization rates) is the best way to manage DBM and other pests of cruciferous crops. Introduction of glucosinolate-sulphatase inhibitors as plant-incorporated-products or sprayable material may also lead to a novel pest management strategy.     

Stability of field-selected resistance to insecticides in Plutella xylostella (Lep., Plutellidae) from Pakistan

Abstract:  To investigate fluctuation in susceptibility to insecticides, natural populations of Plutella xylostella were collected from the same field in the region of Multan, Pakistan, in late summer, mid-winter and early spring. After bulking up for a generation in the laboratory, the populations were examined against pyrethroids and organophosphates as well as newer insecticides (spinosad, indoxacarb and emamectin). Each population showed a broad range of variation in susceptibility to all chemicals. Comparison between populations collected in different times of years in 2003 and 2004 showed variation in susceptibility to organophosphates and pyrethroids. In winter, susceptibility to organophosphates increased, whereas it decreased in relation to pyrethroids. However, susceptibility to the newer insecticides was unchanged within the season. The results suggest that the fluctuation observed in susceptibility could be either associated with fitness costs of organophosphate and pyrethroids or cessation of insecticides. These results might have important implications in resistance management. We propose a strategy for application of insecticides in relation to P. xylostella management in Pakistan.     

小菜蛾卵寄生蜂在生态恢复条件下的自然增长

在生态恢复的深圳龙岗生态示范农场,自然寄生于小菜蛾卵的寄生蜂种类逐渐年多1999年9月,首次发现卷蛾分索赤眼蜂（Trichogrammatoidea bactrae)和玉米螟赤眼蜂（Trichogramma ostriniae)自然寄生于田间小菜蛾卵;同时,拟澳洲赤眼蜂（Tichogramma confusum)和碧岭赤眼蜂（Trichogramma bilingensis)在田间也有一定的自然寄生比率。目前,4种赤眼蜂已经在田间自然建立了种群,其中以拟澳洲赤眼蜂数量占优势小菜蛾的自然寄生率为15％,最高时可达29％。表明农田生态条件的恢复对小菜蛾卵寄生蜂有较好的增殖和保护作用,最后提出了在该农场利用赤眼蜂自然控制小菜蛾种群的可能性。     

小菜蛾对苦皮藤素抗性选育及交互抗性测定

敏感小菜蛾Plutella xylostella (L.)经苦皮藤素20代的抗性选育,其抗性增长21.57倍。选育的小菜蛾抗性品系对杀虫双、杀螟丹和叶蝉散分别有4.63、4.11和3.71倍的交互抗性;对溴氰菊酯、氯菊酯、氯氰菊酯分别有0.22、0.01和0.26倍的负交互抗性。高抗杀螟丹、杀虫双小菜蛾品系对苦皮藤素无明显交互抗性,而高抗溴氰菊酯小菜蛾品系对苦皮藤素有3.61倍的交互抗性。     

小菜蛾对九种杀虫剂的抗药性

采用叶片药膜法测定了9种杀虫剂对海南、山东、广东、湖北武汉和襄樊等5个地区小菜蛾Plutella xylostella(L.)田间种群的毒力,和室内相对敏感品系比较。结果显示,5个地区的小菜蛾种群都对氯氰菊酯产生了10倍以上的抗性,广东和山东种群达到30倍以上的抗性。对阿维菌素的抗性山东小菜蛾种群达到135倍,广东种群达到30倍,其他地区均在10倍以下。但是,作用机制与阿维菌素类似的药剂,氟虫腈的抗性5个地区均在5倍或5倍以下。对昆虫生长调节剂定虫隆和氟虫脲的抗性除广东种群分别在10倍和20倍以上外,其他地区均在5倍以下。广东种群对多杀菌素的抗性为7.8倍,其他地区的种群没有产生抗性,多杀菌素和杀虫双均为作用于乙酰胆碱受体的药剂,但是作用的位点不同。杀虫双对5个种群的LC50值均是比较大的(>800 mg/L),尽管没有明显的抗性,不适宜用于小菜蛾田间防治。对呼吸链电子转移抑制剂溴虫腈的抗性均在10倍以下。对辛硫磷的抗性在2~5倍。     

Interspecific competition between Diadegma semiclausum Hellen (Hym., Ichneumonidae) and Cotesia plutellae (Kurdjumov) (Hym., Braconidae) in parasitizing Plutella xylostella (L.) (Lep., Plutellidea)

Abstract:  Interspecific competition between Diadegma semiclausum and Cotesia plutellae was investigated at 25°C in the laboratory, by exposing the third instar larvae of the diamondback moth, Plutella xylostella to both species together, either species alone or by exposing the host larvae already parasitized by one species, at different intervals, to the other. When host larvae were exposed simultaneously to two species in one arena, parasitism rates of the host by each species were not reduced by the presence of the other species; joint parasitism rate by two species was not significantly higher than that by either parasitoid alone. Both parasitoids could lay eggs into the host larvae which had previously been parasitized by the other species, leading to the occurrence of multiparasitized hosts. When host larvae were parasitized first by D. semiclausum and then being followed within 1–2 h by exposing to C. plutellae , or vice versa, ensuing parasitoid cocoons from the multiparasitized host larvae were nearly all C. plutellae . When host larvae were parasitized initially by C. plutellae and then being followed by D. semiclausum two or more days later, all parasitoids ensued from the multiparasitized hosts were C. plutellae . In contrast, when host larvae were parasitized initially by D. semiclausum and then being followed by C. plutellae two or more days later, most host larvae could not survive to prepupae and most of the ensuing parasitoid adults from the surviving hosts were D. semiclausum . Dissections of host larvae at various time intervals after parasitization by the two parasitoids showed that development of both parasitoids in multiparasitized hosts were somewhat arrested, and that the first instar larvae of C. plutellae could initiate a physical attack on the larvae of D. semiclausum and remove the latter.     

小菜蛾抗药性及其治理对策的研究进展

小菜蛾（Plutella xylostella L.）的抗药性研究是一项全球性的重要课题。本从其抗药性发展、抗药性机理研究进展、抗药性检测及研究手段的状况、抗药性治理对策等方面,对小菜蛾抗药性的研究进展进行综述。目前,对小菜蛾抗药性的分子水平上的探讨甚少。     

Occurrence of diamondback moth,Plutella xylostella (Lepidoptera: Plutellidae), and its larval parasitoids across Saskatchewan,Canada

The prevalence of the diamondback moth and its larval parasitoids, was explored across Saskatchewan, Canada. Higher numbers of diamondback moths were recorded early in the season than later and in the Mixed Grassland compared to three other ecoregions. The highest proportion of parasitism was observed in the Boreal Transition ecoregion in early season.     

Detection of insecticide resistance in Plutella xylostella (L.) (Lepidoptera: Plutellidae) populations in South Australian crucifer crops

In response to reports of failures of sprays to control Plutella xylostella infestations in vegetable-growing areas around Adelaide in 1991, the extent of resistance to six insecticides in several South Australian populations of P. xylostella was determined. Populations sampled from vegetable crops in the Adelaide region were five- to 200-fold resistant to organophosphates (chlorpyrifos, methamidophos and mevinphos), eight- to 400-fold resistant to pyrethroids (esfenvalerate and permethrin) and six-fold resistant to the carbamate methomyl compared with a susceptible strain. Mevinphos and esfenvalerate were the most effective of the tested insecticides. These, together with Bacillus thuringiensis products, have continued until 1998 to be used almost exclusively for the control of P. xylostella in South Australian vegetable crops in the absence of any resistance management strategy.     

小菜蛾溴氰菊酯敏感和抗性品系蛋白质表达谱的比较分析

杀虫剂抗性是害虫防治中的一个主要挑战。为有效治理抗性, 我们必须了解杀虫剂诱导的害虫生理生化变化。目前害虫抗药性的一些机理已经清楚, 但更多的相关机制还有待探究。本研究通过蛋白质组学方法检测了小菜蛾Plutella xylostella溴氰菊酯敏感和抗性品系间蛋白质组的表达差异。结果显示： SDS-PAGE胶上有大约300个蛋白差异点, 其中23个蛋白点具2.5倍以上的表达差异, 通过MALDI-TOF-MS, 我们成功鉴定出8个蛋白, 其中包括化感蛋白CSP2、 铜锌超氧化物歧化酶和peroxiredoxin样蛋白。通过实时定量PCR（real-time quantitative PCR, qPCR）分析了其中5个蛋白的mRNA 表达水平, 结果表明mRNA 表达水平不能真实反映蛋白的表达水平。免疫印迹验证了双向电泳中SOD1的表达差异。本研究有力地证明溴氰菊酯诱导小菜蛾成虫蛋白质组表达变化, 这为进一步筛选抗性靶标提供很大的帮助。     

高温对抗性和敏感小菜蛾生命表参数及后代杀虫剂敏感性的影响

为研究高温对抗性和敏感小菜蛾Plutella xylostella生物学适合度及抗药性进化的影响,本研究测定了温度对杀虫剂抗性和敏感小菜蛾实验种群生命表参数及后代对阿维菌素敏感性的影响。 结果表明：与25℃相比,33.5℃条件下抗性和敏感种群的平均世代历期（D）、净生殖率（R₀）、内禀增长率（r_m）、周限增长率（λ）值、总产卵量、雌蛾平均寿命、日产卵量和孵化率均显著下降。 在25℃下,抗性和敏感种群的r_m,λ,D和日产卵量无显著差异,但抗性种群的R₀略低于敏感种群（为敏感种群的87%）。 在33.5℃下,抗性种群的r_m和R₀显著低于敏感种群（分别为敏感种群的75%和64%）,抗性种群雌成虫寿命、总产卵量和孵化率显著也低于敏感种群。 抗性种群在33.5℃下饲养一代后,后代对阿维菌素的抗性水平大幅下降,而相同处理下敏感种群对阿维菌素的抗性水平没有显著下降。 上述结果表明,无论在常温还是高温条件下,抗性种群生物学适合度均低于敏感种群,尤其是高温下抗性种群适合度远低于敏感种群。 抗性种群经高温饲养一代后对阿维菌素的抗性水平大幅下降可能与高温下抗性种群适合度显著较低有关。     

Sublethal effects of hexaflumuron on development and reproduction of the diamondback moth,Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract Effects of hexaflumuron at 10% lethal concentration (LC₁₀) and LC₂₅ on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC₅₀, LC₁₀ and LC₂₅ values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre‐pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre‐adult stages declined significantly at LC₂₅ concentration. Reproduction parameters such as reproductive rate (R₀) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC₁₀ concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.     

Seasonal population fluctuations of the diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae) on different cauliflower cultivars

The diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, it has been identified as a serious pest of the cauliflower fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported until now. According to many researchers, to solve the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. Despite this condition, it seems that the use of resistant cauliflower cultivars is an appropriate policy for integrated control of the pest in the field. In order to identify the most resistant cultivar in the field, eight cauliflower cultivars in a completely randomised design with five replicates were planted at the Shahed University research field (south of Tehran). Density of eggs, larvae and pupae of P. xylostella were measured every 10 days in these cultivars. The results showed that there is no significant difference between numbers of eggs per plant on different cultivars. But number of larvae and pupae per plant were significantly different among different cultivars. Smilla and Snow mystique cultivars had the highest number of larvae and pupae. On the other hand, Buris and Snow crown cultivars had the lowest number of pupae and Snow crown and SG cultivars had the lowest number of larvae per plant. According to the results, the Buris and Snow crown cultivars had the lowest infestation and had a kind of resistance to pest.     

Tebufenozide resistance is associated with sex‐linked inheritance in Plutella xylostella

The diamondback moth (DBM), Plutella xylostella (L.), is a major pest of cruciferous crops. Tebufenozide, a novel nonsteroidal ecdysone agonist, exhibits good efficacy and has played an increasingly important role in the control of Lepidopteran pests in China. For its resistance management, the genetic basis of tebufenozide resistance was studied using a laboratory selected resistant strain of DBM (resistant ratio, RR = 268). A series of crosses with laboratory susceptible and resistant strains revealed that tebufenozide resistance in this pest was partially biased toward female heredity, with a large difference in RR for F₁ (RR = 29) and rF₁ progeny (RR = 147). The dominance calculated for these 2 cross progeny was ?0.788 and 0.09, respectively. Further analysis showed that the susceptible male and female larvae were similar in their sensitivity to tebufenozide, but the resistant female larvae showed significantly higher resistance than the resistant male larvae. The heredity of tebufenozide resistance in DBM might be linked with the W sex chromosome, which suggested that DBM has the ability to develop high levels of resistance to tebufenozide. This is the first report of sex‐linked inheritance of tebufenozide resistance in P. xylostella (L.).     

A comparison of the host-searching efficiency of two larval parasitoids of Plutella xylostella

1. A host specialist parasitoid is thought to have greater efficiency in locating hosts or greater ability to overcome host defence than a generalist species. This leads to the prediction that a specialist should locate and parasitise more hosts than a generalist in a given arena. The work reported here tested these predictions by comparing the host‐searching behaviour of Diadegma semiclausum (a specialist) and Cotesia plutellae (an oligophagous species), two parasitoids of larval Plutella xylostella. 2. Both parasitoids employed antennal search and ovipositor search when seeking hosts but D. semiclausum also seemed to use visual perception in the immediate vicinity of hosts. 3. Larvae of P. xylostella avoided detection by parasitoids by moving away from damaged plant parts after short feeding bouts. When they encountered parasitoids, the larvae wriggled vigorously as they retreated and often hung from silk threads after dropping from a plant. 4. These two parasitoids differed in their responses to host defences. Diadegma semiclausum displayed a wide‐area search around feeding damage and waited near the silk thread for a suspended host to climb up to the leaf, then attacked it again. Cotesia plutellae displayed an area‐restricted search and usually pursued the host down the silk thread onto the ground. 5. Diadegma semiclausum showed a relatively fixed behavioural pattern leading to oviposition but C. plutellae exhibited a more plastic behavioural pattern. 6. The time spent by the two parasitoids on different plants increased with increasing host density, but the time spent either on all plants or a single plant by D. semiclausum was longer than that of C. plutellae. Diadegma semiclausum visited individual plants more frequently than C. plutellae before it left the patch, and stung hosts at more than twice the rate of C. plutellae. 7. The results indicated that the host‐location strategies employed by D. semiclausum were adapted better to the host's defensive behaviour, and thus it was more effective at detecting and parasitising the host than was C. plutellae.     

小菜蛾及菜蛾绒茧蜂乙酰胆碱酯酶敏感性的相关变化

用生物测定和生化检测的方法,对福州地区小菜蛾Plutella xylostella和菜蛾绒茧蜂Apanteles plutellae的抗药性及两种昆虫乙酰胆碱酯酶对杀虫剂的敏感性进行了田间监测。结果显示,从1998年9月至1999年4月,小菜蛾乙酰胆碱酯酶对6种有机磷和氨基甲酸酯杀虫剂敏感性逐渐恢复,寄生于同一虫源的菜蛾绒茧蜂乙酰胆碱酯酶敏感性的变化也呈明显的相关性,但菜蛾绒茧蜂乙酰胆碱酯酶的敏感性高于其寄主小菜蛾。脱离选择压力后,两种昆虫对杀虫剂的敏感性迅速恢复,乙酰胆碱酯酶的K_i值显著增高。对乙酰胆碱酯酶的K_m、V_max和K_i值测定结果表明,两种昆虫对有机磷和氨基甲酸酯杀虫剂的抗性与乙酰胆碱酯酶对杀虫剂的不敏感性有关。此外还研究了不同发育期小菜蛾乙酰胆碱酯酶活性及其K_i值的变化。探讨了在杀虫剂选择压力下,两种昆虫乙酰胆碱酯酶敏感性的环境适应性变化机制。     

小菜蛾有机磷护性季节性变化及毒理机制研究

1998～ 2 0 0 3年期间的田间监测结果显示 ,福州地区小菜蛾 Plutella xylostella对甲胺磷和敌敌畏的抗性水平呈季节性变化 ,每年春秋季的抗性水平显著高于夏季 7月期间的抗性水平。与 2 5℃ 2 d的饲养条件相比 ,35℃ 2 d和 5℃ 30 d可使小菜蛾羧酸酯酶 (Car E)和谷胱甘肽 - S-转移酶 (GST)活力显著抑制 ,35℃ 2 d还可使小菜蛾乙酰胆碱酯酶 (ACh E)活力显著抑制 ,但 5℃4 d对小菜蛾 ACh E、Car E和 GST活力影响差异不显著。当反应温度均为 2 5℃时 ,在 35℃ 2 d、2 5℃ 2 d和 5℃ 30 d下饲养的小菜蛾 ACh E对甲胺磷和克百威的敏感性 (K i值 )没有明显变化 ,但酶与杀虫剂在 37℃的反应温度下 ,甲胺磷、敌敌畏和克百威对在 2 5℃下饲养的小菜蛾 ACh E的抑制作用显著增高。上述结果表明环境温度会影响小菜蛾的解毒代谢及杀虫剂对 ACh E的抑制作用。探讨了环境温度的季节性变化对田间小菜蛾有机磷抗性水平影响的毒理学机制。     

高温对田间小菜蛾种群及抗性水平的抑制

田间调查结果表明,6月期间,田间小菜蛾种群密度处于相对较高水平,但在7月初至8月初期间急剧下降,8月下旬开始逐渐升高,9月～11月期间,小菜蛾种群密度显著高于春季的6月及夏季的8月下旬。总体上看,与25°C处理相比,40°C预处理田间小菜蛾8h后,氰戊菊酯、甲胺磷和阿维菌素对田间小菜蛾的24h和48h毒力均显著增高。与25℃处理相比,33．5°C预处理24h、36°C预处理8h和36℃预处理24h均显著抑制田间小菜蛾多功能氧化酶活性,且随着高温处理时间延长,抑制率明显增大。上述结果表明,夏季高温可导致田间小菜蛾种群密度急剧下降,并会显著抑制田间小菜蛾对杀虫剂的抗性水平及多功能氧化酶活性。     

Screening of oilseed rape cultivars relation to diamondback moth,Plutella xylostella (Lep.: Plutellidae) in fields of Tehran

The diamondback moth (DBM), Plutella xylostella (L.) (Lep., Plutellidae), is one of the most important pests of oilseed rape, Brassica napus L., in the world. In this study, resistance of oilseed rape cultivars to DBM was evaluated in fields of Tehran based on injury rate of the cultivars. To evaluate cultivar resistance, 19 cultivars of oilseed rape were planted in randomised complete-block design with three replications. Total experiments were conducted in experimental field of Shahed University. Results showed that DBM had activity on the plants during season and peak of the injury occurred on 27 May. Results indicated that the total of oilseed rape cultivar was spotty. Statistical analysis showed that there was significant difference among determined characteristics in all cultivars. The highest and lowest numbers of holes in the leaf were observed in Midas, Karaj3, Zarfam and Hyola420, Hyola308 cultivars, respectively, in sampling of the end growth. Opera and Midas cultivars have the highest percentage of leaf infestation and the lowest percentage of leaf infestation was observed in Hyola420 and Hyola308. Also, Karaj3 and Zarfam cultivars have the highest percentage of meristem infestation and the lowest percentage of meristem infestation was observed in Licard and Hyola420 cultivars. Based on peak of the injury rate and importance of meristem injury, Hyola420 and Hyola308 cultivars were relatively resistant to DBM, and Karaj3 and Zarfam were relatively sensitive to DBM.     

Biological and Integrated Control of Plutella xylostella (Lep., Yponomeutidae) and Crocidolomia pavonana (Lep., Pyralidae) in Brassica Crops in Papua New Guinea

The major constraint to the production of good quality cabbage in Papua New Guinea (PNG) is posed by a complex of insect pests which includes the Diamondback Moth Plutella xylostella (L.) as the most prominent species. In order to evaluate the prospects of a classical control approach economically important major pests and their natural enemies were surveyed in three cabbage growing areas with distinct climatic regimes at low-, mid- and high-elevation. In the PNG highlands (Goroka and Tambul area, Western Highlands Province) the release and successful establishment of the P. xylostella -specific parasitoid Diadegma semiclausum (Hellen) reduced crop losses remarkably since 1995. Favourable circumstances, such as continuous brassica cultivation and low status of associated lepidopteran pests, particularly at Tambul (2400 m above sea level) with an almost temperate climate, were supportive for this approach. In the arid PNG lowlands (Laloki area, Central Province) the introduced P.xylostella -parasitoid Cotesia plutellae (Kurdjumov) exerted 80% parasitism in an experimental site, although a lasting establishment was not achieved in that location. Among several indigenous P. xylostella parasitoids Brachymeria phya (Walker) was a ubiquitous species but did not reduce the pest status of its host. Natural enemies of associated lepidoptera such as Crocidolomia pavonana (Zeller), Spodoptera litura (F.), Helicoverpa armigera (Hübner) and Hellula undalis (F.) were economically insignificant. Thus, insecticidal control, preferably selective, was still a requirement. In comparison to Bacillus thuringiensis -products (Delfin ® and Thuricide ® ) and the synthetic insect growth regulator Chlorfluazuron (Atabron ® ), best results were achieved in field trials with the commercial neem formulation NeemAzal ® ( Azadirachta indica A. Juss.) and an aqueous neem seed kernel extract from seeds of PNG grown trees. Besides its high efficacy against lepidopterous pests, neem also controlled the false mustard aphid Lipaphis erysimi (Kalt.), being of economic importance in the arid PNG lowlands. The prospects of integrating C. plutellae into a reduced insecticide spraying program as well as alternative cultural control measures are discussed.