English field samples of Thrips tabaci show strong and ubiquitous resistance to deltamethrin

BACKGROUND: Onion thrips, Thrips tabaci Lindeman, is a prevalent pest of glasshouse and field vegetables, such as leeks and salad onions. Pesticides are the main option for control, but this approach risks the evolution and spread of insecticide resistance. In the light of anecdotal reports in the United Kingdom of poor efficacy of pyrethroids against T. tabaci, thought to be primarily a consequence of resistance, the responses to deltamethrin of ten English samples of T. tabaci, collected from field leeks and salad onions in 2006, were measured to establish the level and prevalence of potential resistance to this compound. RESULTS: All the samples showed significant deltamethrin resistance that was comparable or slightly lower than the maximum level reported previously for T. tabaci from New Zealand. CONCLUSION: The mechanism(s) conferring deltamethrin resistance remain unknown at present but are likely to extend to other synthetic pyrethroids approved for use against this species. The findings suggest that these compounds are unlikely to give satisfactory control of T. tabaci in England and have stimulated the recommendation to use alternatives. Copyright © 2010 Society of Chemical Industry     

不同杀虫剂对烟蓟马的室内毒力与田间防效

烟蓟马是一种世界性害虫,为筛选出高效低毒的药剂,采用叶管药膜法测定了不同药剂对烟蓟马的室内毒力,并开展了田间防效试验。室内毒力测定结果表明,对成虫活性最高的药剂是阿维菌素、乙基多杀菌素和虫螨腈,其LC₅₀均小于1 mg/L;多杀霉素的毒力也较高,其LC₅₀为2.11 mg/L;吡丙醚对2龄若虫表现较高毒力。田间试验结果表明,2.5%高效氯氟氰菊酯SC、10%虫螨腈SC和60 g/L乙基多杀菌素SC对烟蓟马药后3~14 d的防效均达90%以上,除100 g/L吡丙醚SC外,其他药剂药后14 d的防效均达80%以上。2.5%高效氯氟氰菊酯SC、10%虫螨腈SC和60 g/L乙基多杀菌素SC可作为防治烟蓟马的首选药剂,并交替使用其他药剂。     

Resistance of Thrips tabaci to pyrethroid and organophosphorus insecticides in Ontario, Canada

Onion thrips, Thrips tabaci Lindeman, were collected from commercial onion fields in 2001, 2002 and 2003 to assess resistance to lambda-cyhalothrin, deltamethrin and diazinon. In 2001, six of eight adult populations were resistant to lambda-cyhalothrin, with resistance ratios (RR) ranging from 2 to 13.1 and four of these were also resistant to deltamethrin, with RR ranging from 19.3 to 120. Three of four adult populations were resistant to diazinon with RR ranging from 2.5 to 165.8. In 2002, four of seven nymphal populations and three of six adult populations were resistant to deltamethrin, with RR ranging from 4.3 to 72.5 and 9.4 to 839.2, respectively. Only one of six nymphal populations and one of five adult populations were resistant to diazinon, with RR of 5.6 and 2.3, respectively. In 2003 diagnostic dose bioassays, 15 of 16 onion thrips populations were resistant to lambda-cyhalothrin and all were resistant to deltamethrin. Eight of the 16 were resistant to diazinon. These results indicate that insecticide resistance is widespread in onion thrips in commercial onion fields in Ontario.     

Development of a bioassay system for monitoring susceptibility in Thrips tabaci

A system is described for collecting adult and larva of Thrips tabaci from onion foliage into insecticide-treated vials to evaluate susceptibility to insecticides. The thrips insecticide bioassay system (TIBS) allows one to treat vials and store them for 3 weeks before thrips are collected. Depending on the population density in the field, collection of the insects for the test required from 3-6 h for one person. Assays are read after 24h. This system was used in 1997 and 1998 in commercial onion fields in Honduras and Nicaragua, and TIBS was sensitive enough to detect differences to the insecticides tested, to thrips life stages and to different generations within an onion-growing season. Data collected suggest that there were not serious problems with thrips insecticide resistance, with the possible exception of cypermethrin in Nicaragua which had a resistance ratio (RR) value of 26.9 for adult thrips. The largest RR values were observed at the end of the growing season, and this may be caused by the season-long selection by insecticide sprays. The mortality of adults and larvae followed the same general pattern, but the ratio between larvae and adults differed for each chemical group.     

总评“归一值”在多杀菌素·甲氨基阿维菌素苯甲酸盐聚乳酸微球制备工艺优化中的应用

采用溶剂蒸发法制备了多杀菌素·甲氨基阿维菌素苯甲酸盐聚乳酸微球,考察了内相聚乳酸浓度(X1)、理论载药量(X2)和搅拌速率(X3)对微球载药量、包封率、粒径、跨距及5 d释放率的影响。用数学方法将试验设计中的多指标"归一"化,采用中心多点等距设计法,对各指标以及总评"归一值"进行二项式拟合,描绘三维效应面,用Design-expert V8.06软件对总评"归一值"较佳的试验条件进行预测。结果表明,当聚乳酸质量浓度和搅拌速率减小、以及理论载药量增大时,总评"归一值"增大。经预测,当聚乳酸质量浓度为77.79 mg/mL、理论载药量(质量分数)为51.06%、搅拌速率为560.91 r/min时,总评"归一值"理论值达到最大(0.681 1)。依据上述较佳条件制备的微球总评"归一值"实测值为0.630 8,与理论预测值的偏差为-5.03%,其中包封率为84.49%,粒径7.19μm,跨距为1.134,5 d释放率为52.95%。微球表面光滑,DSC测试结果表明,其有效成分与微球骨架结合完好。表明研究建立的数学模型可用来预测多杀菌素·甲氨基阿维菌素苯甲酸盐聚乳酸微球的较优配方。     

Effects of a juvenile hormone analog,pyriproxyfen, on Thrips tabaci (Thysanoptera: Thripidae)

Effects of a juvenile hormone analog, pyriproxyfen, on various developmental stadia of the onion thrips, Thrips tabaci Lindeman, were determined on cabbage leaves in the laboratory. Pyriproxyfen was applied at 0.064 or 0.128 g AI liter(-1) on leaves (residual contact-ingestion), thrips (direct contact) and leaf-thrips (residue contact-ingestion-direct contact). Pyriproxyfen did not have any significant lethal effects on thrips pupae in any treatment. Lethal effects on thrips larvae varied depending on application method and dosage. In the leaf and the leaf-thrips treatments, few larvae and pre-pupae molted to the next stage, and none developed to adults. In contrast, in the thrips-only treatment, pyriproxyfen did not show any significant lethal effects. The developmental times of larvae and pre-pupae were prolonged when larvae were treated with pyriproxyfen, and those of pre-pupae and pupae were shortened when pre-pupae and pupae were treated. The longevity and survival rates of thrips adults were generally shorter when they contacted and ingested pyriproxyfen-treated leaves than those in water control. Significantly fewer progeny (0.22-1.15 larvae per female) were produced by females that had fed on and been in contact with the pyriproxyfen-treated leaves than by those in the water control (11.94 larvae per female). However, the number of progeny produced by the thrips females increased significantly (3.32-7.28 larvae per female) when the females were transferred to untreated leaves after feeding on treated leaves for 5 days; the daily larval hatching pattern was similar to those in water control, indicating that female adults were able to produce viable eggs when untreated food was offered.     

橘小实蝇对甲氨基阿维菌素苯甲酸盐的抗性机制及对其他药剂的交互抗性

入侵害虫橘小实蝇严重为害蔬菜、花卉、水果等经济作物,目前在田间常使用杀虫剂进行防治。为探索甲氨基阿维菌素苯甲酸盐(甲维盐)防控橘小实蝇的抗性风险,采用药膜法测定了橘小实蝇抗甲维盐种群(EB)对8种杀虫剂的交互抗性水平,并测定了橘小实蝇EB种群、金华田间种群(JH)和敏感种群(S)的解毒酶活性。历经33代筛选,橘小实蝇EB种群对甲维盐产生了43.4倍的中等水平抗性,对阿维菌素存在中等水平交互抗性,对吡虫啉、辛硫磷、马拉硫磷存在低水平交互抗性,对噻虫胺、高效氯氟氰菊酯、多杀霉素和虫螨腈未表现出交互抗性。胡椒基丁醚(PBO)、磷酸三苯酯(TPP)和顺丁烯二酸二乙酯(DEM)均可显著提高甲维盐对橘小实蝇EB种群、JH种群和S种群的室内毒力。橘小实蝇EB种群细胞色素P450(3.9倍)和b₅含量(3.3倍)、O-脱甲基酶活性(4.2倍)、谷胱甘肽S-转移酶活性(2.7倍)、羧酸酯酶活性(3.2倍)显著高于S种群。多功能氧化酶、谷胱甘肽S-转移酶、羧酸酯酶活性显著增强可能是橘小实蝇对甲维盐产生高水平抗性的重要机制。     

Monitoring of beet armyworm resistance to spinosad and methoxyfenozide in Mexico

BACKGROUND: Resistance to spinosad and methoxyfenozide has been studied in several insect pests, but there is a lack of information on Spodoptera exigua (Hübner) in Mexico. Therefore, evidence for the development of resistance in this pest to both compounds was examined. The effects of methoxyfenozide on reproductive parameters of S. exigua adults were also determined.RESULTS: Third instars from a field population were exposed for 24 h to the LC(50) of spinosad or methoxyfenozide for over six generations (G(2)-G(7)). No significant reduction in susceptibility to either compound was detected for up to five generations. In G(7), LC(50) values for insects exposed to spinosad and methoxyfenozide were respectively 2.75-fold and 1.25-fold greater than for G(1) larvae. Oral treatment with methoxyfenozide reduced the fecundity and fertility of G(7) adults, confirming sublethal effects on reproduction. Finally, five populations (Se-La Floriza, Se-Lazareto, Se-Bachigualato, Se-Los Agustinos and Se-Villa de Arista) of S. exigua were collected from fields in three states of Mexico for resistance monitoring to spinosad and methoxyfenozide. With the exception of Se-Villa de Arista, the other populations showed significant resistance to spinosad, with resistance ratios between 16- and 37-fold, compared with a susceptible laboratory colony. In contrast, only one population (Se-Lazareto) showed significant resistance to methoxyfenozide (13-fold).CONCLUSION: Resistance management programmes should be established, particularly in areas where S. exigua has developed resistance to spinosad. Copyright (c) 2008 Society of Chemical Industry.     

Cross‐resistance,inheritance and biochemical mechanisms of imidacloprid resistance in B‐biotype Bemisia tabaci

BACKGROUND: The B‐type Bemisia tabaci (Gennadius) has become established in many regions in China, and neonicotinoids are extensively used to control this pest. Imidacloprid resistance in a laboratory‐selected strain of B‐type B. tabaci was characterised in order to provide the basis for recommending resistance management tactics. RESULTS: The NJ‐Imi strain of B‐type B. tabaci was selected from the NJ strain with imidacloprid for 30 generations. The NJ‐Imi strain exhibited 490‐fold resistance to imidacloprid, high levels of cross‐resistance to three other neonicotinoids, low levels of cross‐resistance to monosultap, cartap and spinosad, but no cross‐resistance to abamectin and cypermethrin. Imidacloprid resistance in the NJ‐Imi strain was autosomal and semi‐dominant. It is shown that enhanced detoxification mediated by cytochrome‐P450‐dependent monooxygenases contributes to imidacloprid resistance to some extent in the NJ‐Imi strain. Results from synergist bioassays and cross‐resistance patterns indicated that target‐site insensitivity may be involved in imidacloprid resistance in the NJ‐Imi strain of B. tabaci. CONCLUSION: Although oxidative detoxification mediated by P450 monooxygenases is involved in imidacloprid resistance in the NJ‐Imi strain of B‐type B. tabaci, target‐site modification as an additional resistance mechanism cannot be ruled out. Considering the high risk of cross‐resistance, neonicotinoids should be regarded as a single group when implementing an insecticide rotation scheme in B. tabaci control. Copyright © 2009 Society of Chemical Industry     

Cross‐resistance study and biochemical mechanisms of thiamethoxam resistance in B‐biotype Bemisia tabaci (Hemiptera: Aleyrodidae)

BACKGROUND: B‐biotype Bemisia tabaci (Gennadius) has invaded China over the past two decades. To understand the risks and to determine possible mechanisms of resistance to thiamethoxam in B. tabaci, a resistant strain was selected in the laboratory. Cross‐resistance and the biochemical mechanisms of thiamethoxam resistance were investigated in the present study. RESULTS: A 66.3‐fold thiamethoxam‐resistant B. tabaci strain (TH‐R) was established after selection for 36 generations. Compared with the susceptible strain (TH‐S), the selected TH‐R strain showed obvious cross‐resistance to imidacloprid (47.3‐fold), acetamiprid (35.8‐fold), nitenpyram (9.99‐fold), abamectin (5.33‐fold) and carbosulfan (4.43‐fold). No cross‐resistance to fipronil, chlorpyrifos or deltamethrin was seen. Piperonyl butoxide (PBO) and triphenyl phosphate (TPP) exhibited significant synergism on thiamethoxam effects in the TH‐R strain (3.14‐ and 2.37‐fold respectively). However, diethyl maleate (DEM) did not act synergistically with thiamethoxam. Biochemical assays showed that cytochrome P450 monooxygenase activities increased 1.21‐ and 1.68‐fold respectively, and carboxylesterase activity increased 2.96‐fold in the TH‐R strain. However, no difference was observed for glutathione S‐transferase between the two strains. CONCLUSION: B‐biotype B. tabaci develops resistance to thiamethoxam. Cytochrome P450 monooxygenase and carboxylesterase appear to be responsible for the resistance. Reasonable resistance management that avoids the use of cross‐resistance insecticides may delay the development of resistance to thiamethoxam in this species. Copyright © 2009 Society of Chemical Industry     

Yield of early white cabbage grown under mulch and non-mulch conditions with low populations of onion thrips (Thrips tabaci Lindeman)

The damage caused by Thrips tabaci to a susceptible hybrid of early white cabbage was studied in field experiments undertaken during 2004 and 2005. The three treatments tested were beds of cabbage mulched with: (1) barley straw, (2) hay, and (3) black polyethylene (PE) sheeting. Bare-soil (un-mulched) beds were used as the control treatment. One early and one late experiment were performed in both years. In the early experiments, the mulches were applied at the start of the experiment, whereas in the late experiments the soil was first covered with black polyethylene for approximately 1 month. In both years, the springs were cold and wet, and so the thrips appeared late and their numbers were low. The highest mean actual weight and trimmed weight were recorded for cabbage grown in 2005 under PE mulch (actual early: 995 g, actual late: 1184 g, trimmed early: 870 g, trimmed late: 1056 g). Year 2004 gave lower values (110g for both variables) under barley straw and hay mulch (165 g and 160 g, respectively). There was no evidence of an allelopathic effect of water extracts of either barley straw or hay.     

烟蓟马对不同葡萄品种的选择性及与主要影响因素的相关性

采用自由选择法测定了烟蓟马对9个葡萄品种的选择性,研究其与寄主物理性状和次生物质的关系。结果表明:烟蓟马对‘信侬乐’(高墨实生)的选择性最强,与对其他品种的选择性差异显著;选择性最弱的葡萄品种为‘秋黑’和‘摩尔多瓦’。相关分析结果表明:烟蓟马对葡萄不同品种的选择性,与叶片内的单宁、黄酮和蜡质含量存在显著负相关关系,回归方程分别为y=13.840-8.662x(r=-0.847,F=45.255,P=0.005),y=6.559-0.31x(r=-0.876,F=57.421,P=0.004)和y=13.988-5.081x(r=-0.938,F=122.071,P=0.001);与寄主的可溶性糖含量[y=0.269+0.809x(r=0.746,F=24.552,P=0.002)]、总酚[y=-6.015+2.492x(r=0.834,F=41.195,P=0.007)]和叶片厚度[y=-4.337+28.521x(r=0.430,F=7.044,P=0.033)]存在正相关关系;与叶绿素含量不相关,相关系数分别为R=0.097(P=0.803)。单宁、蜡质和黄酮含量对烟蓟马在葡萄品种上的选择性有较大影响,其含量越高,烟蓟马选择性越弱。     

Insecticide resistance in field populations of Bemisia tabaci (Hemiptera: Aleyrodidae) in West Africa

BACKGROUND: The tobacco whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), has developed a high degree of resistance to several chemical classes of insecticides throughout the world. To evaluate the resistance status in West Africa, eight insecticides from different chemical families were tested using the leaf‐dip method on four field populations collected from cotton in Benin, Togo and Burkina Faso. RESULTS: Some field populations showed a significant loss of susceptibility to pyrethroids such as deltamethrin [resistance ratio (RR) 3–5] and bifenthrin (RR 4–36), to organophosphates (OPs) such as dimethoate (RR 8–15) and chlorpyrifos (RR 5–7) and to neonicotinoids such as acetamiprid (RR 7–8) and thiamethoxam (RR 3–7). Bemisia tabaci was also resistant to pymetrozine (RR 3–18) and to endosulfan (RR 14–30). CONCLUSION: The resistance of B. tabaci to pyrethroids and OPs is certainly due to their systematic use in cotton treatments for more than 30 years. Acetamiprid has been recently introduced for the control of whiteflies. Unfortunately, B. tabaci populations from Burkina Faso seem to be already resistant. Because cross‐resistance between these compounds has never been observed elsewhere, resistance to neonicotinoids could be due to the presence of an invasive B. tabaci biotype recently detected in the region. Copyright © 2010 Society of Chemical Industry     

草地贪夜蛾对甲氨基阿维菌素苯甲酸盐和虱螨脲的抗性风险评估

甲氨基阿维菌素苯甲酸盐(甲维盐)和虱螨脲是目前生产上防治草地贪夜蛾的主要杀虫剂,为评估其抗性风险,以福建省草地贪夜蛾田间种群为研究对象,在实验室抗性汰选品系选育基础上,采用数量遗传学域性状分析法并结合交互抗性测定,进行草地贪夜蛾对上述两种杀虫剂的抗性风险评估。结果表明：非连续汰选11代和10代后,草地贪夜蛾对甲维盐(F₁₁)和虱螨脲(F₁₀)的抗性倍数分别达30.57倍和11.35倍;抗性现实遗传力分别为0.403和0.555,且前半段筛选的抗性遗传力都远大于后半段;药剂在室内对草地贪夜蛾致死率为50%～90%时,对甲维盐和虱螨脲抗性倍数上升10倍需要汰选8～15代和6～12代。交互抗性测定显示,甲维盐汰选品系对氯虫苯甲酰胺、虱螨脲、虫螨腈无交互抗性,对茚虫威和乙基多杀菌素存在一定交互抗性。虱螨脲汰选品系对氯虫苯甲酰胺、甲维盐、茚虫威、虫螨腈和乙基多杀菌素均无交互抗性。结果表明：草地贪夜蛾对甲维盐和虱螨脲存在快速产生抗性的风险,但可通过与无交互抗性药剂轮用来延缓抗性发展。     

7种杀虫剂对北京地区烟粉虱成虫毒力的比较研究

本试验比较测定了7种杀虫剂对北京地区烟粉虱成虫的毒力,以期为北京地区高毒农药淘汰提供参考。结果表明:氟虫腈对烟粉虱成虫的毒力最强,其LC50值为2.98(g/mL;新烟碱类杀虫剂啶虫脒、吡虫啉对烟粉虱成虫的生物活性较好,LC50值分别为8.04(g/mL、7.49(g/mL,噻虫嗪对烟粉虱成虫毒力相对较差,LC50值仅为95.03(g/mL;烟粉虱成虫对马拉硫磷、异丙威和噻嗪酮3种杀虫剂不敏感。在北京地区,采用噻虫嗪、马拉硫磷、异丙威和噻嗪酮等杀虫剂,不能有效防治烟粉虱的成虫;氟虫腈、吡虫啉和啶虫脒可以用来防治烟粉虱成虫。