Cross‐resistance,mode of inheritance and stability of resistance to emamectin in Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) is a cosmopolitan pest that has developed resistance to several insecticides. The aim of the present study was to establish whether an emamectin‐selected (Ema‐SEL) population could render cross‐resistance to other insecticides, and to investigate the genetics of resistance. RESULTS: Bioassays at G₁ gave resistance ratios (RRs) of 80‐, 2980‐, 3050‐ and 2800‐fold for emamectin, abamectin, indoxacarb and acetamiprid, respectively, compared with a laboratory susceptible population Lab‐PK. After three rounds of selection, resistance to emamectin in Ema‐SEL increased significantly, with RRs of 730‐fold and 13‐fold compared with the Lab‐PK and unselected (UNSEL) population respectively. Further studies revealed that three generations were required for a tenfold increase in resistance to emamectin. Resistance to abamectin, indoxacarb, acetamiprid and emamectin in UNSEL declined significantly compared with the field population at G₁. Furthermore, selection with emamectin reduced resistance to abamectin, indoxacarb and acetamiprid on a par with UNSEL. Crosses between Ema‐SEL and Lab‐PK indicated autosomal and incomplete dominance of resistance. A direct test of a monogenic model and Land's method suggested that resistance to emamectin was controlled by more than one locus. CONCLUSION: Instability of resistance and lack of cross‐resistance to other insecticides suggest that insecticides with different modes of action should be recommended to reduce emamectin selection pressure. Copyright © 2010 Society of Chemical Industry     

斜纹夜蛾幼虫游泳行为初步观察

在实验条件下,初步观察了斜纹夜蛾幼虫游泳行为,结果表明:(1)幼虫泳姿有侧面游泳、弹射游泳、平行游泳和仰面游泳4种姿势;(2)游泳总时间因温度不同而异;(3)仰面游泳持续时间最短,时间分配率和发生率最低。观察结果可为深入研究该幼虫游泳行为及生理机制提供参考。     

Efficacy of insecticide mixtures against pyrethroid‐ and organophosphate‐resistant populations of Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) is an important pest worldwide, with over 112 host plants, and is exposed to insecticides throughout the year, resulting in the rapid development of resistance. Insecticide mixtures can delay the development of resistance more effectively than sequences or rotations. Cypermethrin, deltamethrin, profenofos, chlorpyrifos and fipronil were assessed separately and in mixtures against laboratory susceptible S. litura and two field‐collected populations. RESULTS: The field‐collected population from Khanewal (KWL) was significantly more resistant to cypermethrin, deltamethrin, chlorpyrifos and profenofos than one collected from Muzaffar Garh (MGH). Mixtures of cypermethrin + chlorpyrifos or profenofos and of deltamethrin + chlorpyrifos or profenofos at 1:1, 1:10 and 1:20 ratios significantly increased (P < 0.01) toxicity to cypermethrin and deltamethrin in field populations. The combination indices of cypermethrin + chlorpyrifos at 1:1 and 1:10 ratios and cypermethrin + fipronil at 1:1, 1:10 and 1:20 ratios for the KWL strain and of cypermethrin + profenofos or fipronil at 1:1, 1:10 and 1:20 ratios for MGH were significantly below 1, suggesting synergistic interactions. The inhibitors DEF and PBO largely overcame resistance to deltamethrin, cypermethrin and profenofos, suggesting that resistance to the insecticides was associated with esterase and monooxygenase detoxification respectively. CONCLUSION: Chlorpyrifos, profenofos and fipronil could be used in mixtures to restore cypermethrin and deltamethrin susceptibility. These findings may have considerable practical implications for S. litura resistance management. Copyright © 2008 Society of Chemical Industry     

取食不同食料对斜纹夜蛾后代抗药性的影响

测定了溴氰菊酯对斜纹夜蛾抗性品系和敏感品系取食人工饲料、棉花、大豆和烟草的后代的毒力,及其后代体内的多功能氧化酶和酯酶活性。结果表明,在抗性和敏感品系中,取食不同食料的斜纹夜蛾后代对溴氰菊酯的敏感性顺序均为:烟草<棉花<大豆<人工饲料。在抗、感品系中,无论是中肠还是脂肪体,取食棉花、烟草和大豆的斜纹夜蛾后代多功能氧化酶O-脱甲基活性和酯酶活性均较取食人工饲料的斜纹夜蛾后代的要高,表明这3种寄主植物对斜纹夜蛾的多功能氧化酶和酯酶的活性均有不同程度的诱导性。     

球孢白僵菌对斜纹夜蛾高毒菌株筛选与制剂的研发

斜纹夜蛾Spodoptera litura是一种危害极大的农业害虫,为了探索1条可持续、无污染的新型防治方法,我们通过标准喷塔法从12株球孢白僵菌Beauveria bassiana中筛选出1株对斜纹夜蛾2龄幼虫高毒力的菌株--球孢白僵菌Bb2860菌株.在喷雾浓度为(2592±275)孢子·mm-2的高浓度下,菌株Bb2860对斜纹夜蛾2龄幼虫在第7d的校正死亡率达82.43%±6.03%.不同制剂的室内生测试验表明,孢子水悬液和2种油剂(分别为不含稳定剂和含有稳定剂)在中浓度319～529孢子·mm-2的喷雾浓度下,7d后对斜纹夜蛾2龄幼虫的累计死亡率分别为54.8%、70.0%和76.7%;菌药协同作用为86.8%.另外,于2009年9月在安徽马鞍山进行自然条件下对花椰菜叶上斜纹夜蛾幼虫的田间小区药效试验.处理9d后,纯菌剂的相对防效为77.64%;低剂量和常规用量5%氟啶脲(抑太保)的相对防效分别为49.02%和89.70%;菌药混用的相对防效为91.13%.本研究显示出利用球孢白僵菌制剂及其与低剂量抑太保混用防治斜纹夜蛾的良好应用前景.     

斜纹夜蛾化学感受蛋白SlitCSP2的表达模式定位及配体结合特性分析

研究斜纹夜蛾Spodoptera litura化学感受蛋白Slit CSP2的表达模式、组织定位及与配体结合特性,为揭示SlitCSP2在化学通讯中的功能提供理论依据。利用RT-qPCR检测了SlitCSP2在蛹及雌、雄成虫各组织的基因表达水平;Westernblot方法检测了SlitCSP2在幼虫期和雄成虫头部、触角和足部的蛋白表达水平;利用免疫组织化学技术对Slit CSP2在幼虫各龄期的分布情况进行定位分析;利用荧光竞争结合试验检测Slit CSP2与13种非挥发性化合物的结合特性。RT-qPCR结果表明,SlitCSP2在3龄幼虫表达量最高,3～6龄表达量逐渐降低;成虫阶段雄成虫足部及胸部和雌成虫头部及翅的表达量最高,且雄成虫头部、足部和胸部的表达量显著高于雌成虫。Western blot结果显示,SlitCSP2在3龄幼虫头部（去触角）的蛋白表达水平较高。免疫组化结果表明,Slit CSP2在幼虫阶段主要分布于头部、口器和胸足;在雄成虫中,Slit CSP2主要分布于足部前跗节和足部外骨骼内侧。荧光竞争结合试验表明,Slit CSP2与单宁（Ki=1.77）、花青素（Ki=2...     

Insecticidal activity of destruxin, a mycotoxin from Metarhizium anisopliae (Hypocreales), against Spodoptera litura (Lepidoptera: Noctuidae) larval stages

BACKGROUND: The cyclodepsipeptide destruxin produced by the entomopathogen Metarhizium anisopliae (Metch.) was administered by different methods, topical application, ingestion and a combination of the two, in an attempt to minimize the mycotoxin dose for efficient management of the insect pest Spodoptera litura (Fab.).RESULTS: The insecticidal activity of destruxin on the larval stages of S. litura showed an ascending trend in LD(50) values with increasing age. The value for 12-day-old larvae in the combined application assay was as low as 0.045 microg g(-1) body weight of crude destruxin from M-19 strain when compared with the corresponding values of 0.17 microg g(-1) body weight in the ingestion assay and 0.237 microg g(-1) body weight in the topical application assay. On the other hand, values were higher in the treatments with crude destruxin from the low-virulence M-10 strain of M. anisopliae showing the least quantities of A and E components of destruxin.CONCLUSION: Laboratory bioevaluation showed the combination assay of ingestion and topical application of crude destruxin to be efficient in enhancing its insecticidal properties. The adopted combination assay apparently simulates application of the insecticide at field level. Quantitative differences between destruxins from low- and high-virulence strains of M. anisopliae are in accordance with its presumed role in virulence.     

Effects of four host plants on susceptibility of Spodoptera litura (Lepidoptera: Noctuidae) larvae to five insecticides and activities of detoxification esterases

BACKGROUND: The tobacco cutworm, Spodoptera litura (F.), is one of the most destructive polyphagous pests worldwide. The susceptibility of S. litura larvae reared on tobacco, Chinese cabbage, cowpea and sweet potato to phoxim, chlorfenapyr, methomyl, fenvalerate and emamectin benzoate under laboratory conditions was determined. RESULTS: Spodoptera litura larvae reared on tobacco were most tolerant to all insecticides, whereas those that fed on sweet potato were most susceptible. When larvae were reared on each host plant for three generations, the susceptibilities to phoxim of larvae that fed on Chinese cabbage and cowpea were similar, whereas the susceptibility of larvae that fed on sweet potato decreased by the third generation, and on tobacco the susceptibility decreased in each consecutive generation. When nicotine was added to their diet for three consecutive generations, the tolerance of larvae to phoxim increased twofold, and to emamectin benzoate 3.1‐fold, but the tolerance of larvae to fenvalerate and chlorfenapyr did not change. The acetylcholinesterase activities of the larvae that fed on sweet potato and cowpea were greater than the activities of those that fed on Chinese cabbage and tobacco. In contrast, the carboxylesterase activities of the larvae that fed on tobacco and Chinese cabbage were greater than the activities of those that fed on sweet potato and cowpea. The glutathione S‐transferase activities of larvae were highest when they fed on tobacco, followed by Chinese cabbage and cowpea, and the lowest activities were observed when larvae fed on sweet potato. CONCLUSION: Feeding on tobacco or with nicotine added to the diet, the larvae became more tolerant to insecticides, especially to phoxim and emamectin benzoate. Copyright © 2010 Society of Chemical Industry     

Genetics and evidence for an esterase-associated mechanism of resistance to indoxacarb in a field population of diamondback moth (Lepidoptera: Plutellidae)

Bioassays (at generation G2) with a newly collected field population (designated CH3) of Plutella xylostella L. from farmers' fields in the Cameron Highlands, Malaysia, indicated resistance ratios of 813-, 79-, 171-, 498- and 1285-fold for indoxacarb, fipronil, spinosad, deltamethrin and Bacillus thuringiensis toxin Cry1Ac respectively compared with a laboratory susceptible population (Lab-UK). At G2 the field-derived population was divided into two subpopulations: one was selected (G2 to G7) with indoxacarb (indoxa-SEL), while the second was left unselected (UNSEL). A significant reduction in the resistance ratio for each compound was observed in UNSEL at G8. For indoxa-SEL, bioassays at G8 found that selection with indoxacarb gave a resistance ratio of 2594 compared with Lab-UK and of 90 compared with UNSEL. The toxicity of fipronil, spinosad and deltamethrin was not significantly different in indoxa-SEL at G8 compared with G2 but was significantly greater than UNSEL at G8. The toxicity of Cry1Ac was significantly reduced in indoxa-SEL at G8 compared with G2 but was also significantly greater than UNSEL at G8. This suggests that indoxacarb selection maintained resistance to these compounds in the indoxa-SEL population. Synergist studies indicated that resistance to indoxacarb in indoxa-SEL was esterase associated. Logit regression analysis of F1 reciprocal crosses between indoxa-SEL and Lab-UK indicated that resistance to indoxacarb was inherited as an autosomal, incompletely recessive (D(LC) = 0.35) trait. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by a single locus.     

一株莱氏绿僵菌的筛选及其对草地贪夜蛾的毒力

开展草地贪夜蛾病原真菌的筛选和毒力测定可为草地贪夜蛾的绿色防控提供新的生物制剂.本研究从广西南宁田间采集的草地贪夜蛾幼虫僵虫上分离获得一株病原真菌,采用形态学和ITS-rDNA序列分析相结合的方法对该菌株进行了鉴定,并采用浸虫法测定了该菌株对草地贪夜蛾的致病力.结果表明新分离的菌株为莱氏绿僵菌Metarhizium r...     

高效氯氰菊酯与辛硫磷混用防治斜纹夜蛾应用技术研究

对4．5％高效氯氰菊酯乳油与40％辛硫磷乳油混用防治斜纹夜蛾进行了田间试验。结果表明,每667m2用4．5％高效氯氰菊酯乳油20-30mL 40％辛硫磷乳油50mL对斜纹夜蛾 4龄以下幼虫,药后1-7d的防效可达90％以上,优于10％溴虫腈悬浮剂50mL的效果。两者混用具有经济、高效、安全的优点,适合于“无公害”蔬菜上使用,具有推广应用前景。     

双斑青步甲幼虫对草地贪夜蛾幼虫的捕食能力

在云南德宏州芒市玉米田调查发现一种草地贪夜蛾Spodoptera frugiperda（J.E.Smith）的捕食性天敌昆虫双斑青步甲Chlaenius bioculatus Chaudoi,为探究其对草地贪夜蛾的生物防治潜能,在室内条件下测定了双斑青步甲3龄幼虫对草地贪夜蛾6个龄期幼虫的捕食能力。试验结果表明：双斑青步甲3龄幼虫对草地贪夜蛾6个龄期幼虫的瞬时攻击率分别为1.1478、1.3386、1.3949、1.2745、1.3599和1.4227。处置时间分别为0.0036、0.0068、0.0137、0.0554、0.2895、0.4356 d。日最大捕食量分别为278.39、146.30、73.26、18.06、3.45和2.29头。试验表明,双斑青步甲幼虫对草地贪夜蛾具有良好的捕食作用,有应用于生物防治的潜力。     

草地贪夜蛾对小麦和玉米的产卵选择性及其种群生命表

为明确草地贪夜蛾对小麦的产卵选择性及其是否对小麦安全生产构成威胁,本研究以玉米和小麦作为测试寄主,比较分析了草地贪夜蛾对两种作物不同部位的产卵选择性,并利用两性生命表方法研究了取食小麦、玉米对其生命参数的影响。结果表明:草地贪夜蛾更喜欢在玉米上产卵,其在玉米、小麦叶片、玉米和小麦茎秆上的产卵量存在显著差异(df=102,F=15.593,P<0.05),以玉米叶片背面卵块数量(7.11±1.55)块/笼最高;草地贪夜蛾取食小麦可以完成生活史,但幼虫存活率、化蛹率、羽化率和世代存活率低于取食玉米。取食玉米的幼虫发育历期为(16.31±0.15)d,显著高于取食小麦的(14.66±0.12)d,蛹期、蛹重、产卵前期、成虫寿命和世代周期无显著差异。取食小麦羽化出的雌虫寿命、平均单雌产卵量显著高于取食玉米,分别为(16.39±0.40)d、(976.31±57.21)粒和(14.64±0.32)d、(831.57±30.55)粒。生命表参数显示取食玉米的净增殖率为363.14,显著高于小麦的258.63,但内禀增长率、周限增长率和平均世代周期无显著差异。研究结果为草地贪夜蛾在小麦上的预测预报和有效防控提供了基础数据。