Cross-resistance patterns and fitness in fufenozide-resistant diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND: Fufenozide is a novel non‐steroidal ecdysone agonist with good efficacy against diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae). At present, it is widely applied for the control of a range of lepidopterous pests in China. This study compared the activities of fufenozide and 12 other insecticides against unselected and fufenozide‐selected strains of DBM to examine potential patterns of cross‐resistance. The relative fitness of the fufenozide‐selected strain was assessed to provide information pertinent to insecticide resistance management. RESULTS: Compared with the susceptible strain (JSS), the fufenozide‐resistant strain (JSR) showed high cross‐resistance to dibenzoylhydrazines and benzoylphenylureas, low cross‐resistance to abamectin and no cross‐resistance to organophosphates, carbamates and pyrethroids. JSR had a lower reproductive ability and a relative fitness of 0.5 compared with JSS. CONCLUSION: P. xylostella has the potential to develop resistance to fufenozide, albeit at the expense of fitness. Cross‐resistance between the same and other classes of insecticides is of concern, and should be a key consideration when implementing fufenozide‐based control strategies for this species. Copyright © 2011 Society of Chemical Industry     

Genetic basis of resistance and studies on cross-resistance in a population of diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

The genetic basis of abamectin resistance was studied in a strain of the diamondback moth, Plutella xylostella (L), following laboratory selection of a field population collected at Xuanhua, Hebei Province, China. Data from the testing of F1 progeny from reciprocal crosses between abamectin-resistant and abamectin-susceptible strains indicated that resistance might be autosomal and incompletely recessive with a degree of dominance of -0.13. Chi-squared analyses from the response of a backcross of crossed F1 progeny and the resistant strain and F2 progeny were highly significant, suggesting that the resistance was probably controlled by more than one gene. The results of cross-resistance studies showed that there was little cross-resistance between abamectin and four pyrethroid insecticides (deltamethrin, beta-cypermethrin, fenvalerate and bifenthrin) and no cross-resistance between abamectin and the acylureas chlorfluazuron or flufenoxuron.     

Inheritance of resistance to a Bacillus thuringiensis toxin in a field population of diamondback moth (Plutella xylostella)

Inheritance of resistance to the Bacillus thuringiensis Berl. CryIA(b) crystal protein was studied in Plutella xylostella L. (diamondback moth). A field population 50-fold more resistant to CryIA(b) than a control susceptible strain was used. Dose-mortality curves of the resistant population, the susceptible strain and the F₁ from the two reciprocal crosses were compared. Resistance transmission to the F₁ was dependent on the sex of the resistant progenitor. Sex ratio of the survivors to high doses of CryIA(b) in the F₁ of the two reciprocal crosses did not corroborate the preliminary hypothesis of resistance being due to a recessive sex-linked allele. Since, in a previous work, the loss of CryIA(b) binding capacity of resistant insects had been demonstrated, binding to midgut tissue sections from F₁ individuals was also analysed. The presence of binding in all of the F₁ preparations showed that, at least, a recessive autosomal allele was responsible for the loss of binding capacity in the resistant population.     

高效氯氰菊酯对小菜蛾阿维菌素抗性、敏感种群的亚致死效应

在实验室条件下研究了高效氯氰菊酯亚致死剂量LC10(43.44mg/L)(小菜蛾阿维菌素抗性种群)和LC10(12.61mg/L)(敏感种群)对小菜蛾阿维菌素抗性(AV-R)、敏感(AV-S)种群的亚致死效应。结果表明:高效氯氰菊酯亚致死剂量12.61mg/L处理小菜蛾阿维菌素敏感、抗性种群3龄幼虫后,处理组AV-S(SLC10)和AV-R(SLC10)的化蛹率、羽化率显著低于AV-S(ck)对照组,与AV-R(ck)对照组无显著性差异;用高效氯氰菊酯亚致死剂量43.44mg/L处理抗性种群3龄幼虫后,其处理组AV-R(RLC10)的化蛹率、蛹重、羽化率都显著低于对照组。AV-S(SLC10)组的单雌产卵量为176.45±36.11粒,显著高于对照组和处理的抗性种群,AV-R(SLC10)和AV-R(RLC10)组的单雌产卵量与对照组间无显著性差异,AV-S(SLC10)和AV-R(RLC10)组的产卵期明显缩短。AV-S(SLC10)组的内禀增长率(rm)、周限增长率(λ)和净增殖率(R0),显著高于对照和处理的抗性种群。结果表明高效氯氰菊酯亚致死剂量对小菜蛾阿维菌素敏感种群具有一定的刺激增殖作用。     

Inheritance of resistance and cross-resistance to deltamethrin in Plutella xylostella (Lepidoptera: Plutellidae) from Pakistan

A field population of Plutella xylostella (L) from Pakistan was found to be highly resistant to deltamethrin (>500-fold) but had little or no resistance to spinosad, fipronil, indoxacarb, abamectin, Bacillus thuringiensis (Bt) var kurstaki, Bt var aizawai or Cry1Ac when compared with a susceptible laboratory population, Lab-UK. A sub-population was selected for six generations (laboratory G3-G8) with deltamethrin (delta-SEL), while a second sub-population was left unselected (UNSEL). Bioassays at G9 found that selection with deltamethrin gave resistance ratios of >230 compared with UNSEL (>6730 compared with Lab-UK). The delta-selected population showed no apparent cross-resistance to spinosad, fipronil or indoxacarb. Logit regression analysis of F1 reciprocal crosses between delta-SEL and Lab-UK indicated that resistance to deltamethrin in the delta-SEL population was inherited as an autosomal, incompletely dominant (D(LC) = 0.67) trait. A direct test of monogenic inheritance based on a back-cross of F1 progeny with delta-SEL suggested that resistance to deltamethrin was controlled by more than one factor.     

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.     

Rapid report acetamiprid resistance and cross-resistance in the diamondback moth, Plutella xylostella

A 110-fold acetamiprid-resistant Plutella xylostella (L) strain was established after four selection experiments (in five generations) on a 9.5-fold resistant colony in the laboratory. The resistant strain did not show cross-resistance to chlorfluazuron or Bacillus thuringiensis subsp kurstaki Berliner, but displayed low resistance to cartap and phenthoate.     

Cloning,characterisation and expression profiling of the cDNA encoding the ryanodine receptor in diamondback moth,Plutella xylostella (L.) (Lepidoptera: Plutellidae)

BACKGROUND: The rynodine receptors (RyRs) are the main targets of diamide insecticides such as chlorantraniliprole. To provide the basis for a good understanding of the molecular mechanisms of diamide insecticide resistance, an RyR gene from Plutella xylostella was cloned and characterised in the present paper. RESULTS: A full‐length cDNA sequence of RyR was cloned from P. xylostella through RT‐PCR and rapid amplification of cDNA ends (RACE). The gene (named PxRyR1) is 15 753 bp long, with an open reading frame of 15 354 bp, encoding a predicted RyR of 5117 amino acids. An alternative splicing of the PxRyR1 was also cloned and named PxRyR2. The PxRyR1 shares 77–93% identity with other insect RyRs. Quantitative real‐time PCR analysis showed that the PxRyR was expressed at a high level in second‐instar larvae and adults, at a low level in prepupae and pupae and abundantly in the body wall muscle and head (respectively 6.00 and 3.12 times the expression in the gut). Western blot analysis with anti‐RyR antibodies showed that the RyR was mainly present in the body wall muscle and head, but barely present in the haemocyte and gut. CONCLUSIONS: There are at least two alternative splices of PxRyR expressed in all developmental stages and tissues in P. xylostella at various levels. The results provided the basis for further understanding of the mechanisms of resistance to diamide insecticides in P. xylostella. Copyright © 2012 Society of Chemical Industry     

Insecticidal action of mammalian galectin‐1 against diamondback moth (Plutella xylostella)

BACKGROUND: Previous studies showed that mammalian galectin‐1 (GAL1) could interact with chitosan or chitin, one component of the peritrophic membrane (PM). This finding suggests that the PM could be a target of GAL1, which prompted the authors to explore the effect of GAL1 on larval growth and its potential mechanism. RESULTS: The development of Plutella xylostella (L.) larvae was significantly disturbed after they were fed recombinant GAL1. The histochemical structure and immunostaining pattern suggested that GAL1 treatment resulted in dose‐ and time‐dependent disruption of the microvilli and abnormalities in these epithelial cells. Ultrastructural studies showed that the PM was not present in the midgut of GAL1‐treated insects; instead, numerous bacteria were found in the lumen area. These results indicate that the protective function of the PM was disrupted by GAL1 treatment. Moreover, in vitro data showed that GAL1 interacts with chitosan/chitin in a dose‐dependent manner, and also specifically binds to the PM in vitro. CONCLUSION: In view of the fact that the carbohydrate recognition domain of GAL1 recognises the structural motif N‐acetyl lactosamine (Gal β 1–4 GlcNAc), which is similar to that of chitin (β‐1,4 N‐acetyl‐D ‐glucosamine), it is proposed that the insecticidal mechanism of GAL1 involves direct binding with chitin to interfere with the structure of the PM. Copyright © 2009 Society of Chemical Industry     

氯虫苯甲酰胺对小菜蛾亚致死效应的研究

探讨亚致死剂量氯虫苯甲酰胺对小菜蛾2、3龄幼虫的亚致死效应,为氯虫苯甲酰胺的合理使用提供依据。采用药膜法确定氯虫苯甲酰胺对小菜蛾2龄和3龄幼虫的亚致死剂量(LC25、LC40),以试虫死亡率、取食量、化蛹时间、蛹重、羽化率为指标研究其对小菜蛾的亚致死效应。与对照相比,亚致死剂量氯虫苯甲酰胺处理的小菜蛾除死亡率显著增高外,幼虫生长明显受到抑制,幼虫至化蛹平均历期显著延长,取食量、蛹重和化蛹率明显降低。结果表明亚致死剂量氯虫苯甲酰胺对小菜蛾种群增长有一定抑制作用,对小菜蛾综合防治策略的制定有积极意义。     

Characterisation of abamectin resistance in a field‐evolved multiresistant population of Plutella xylostella

BACKGROUND: Plutella xylostella (L.) has evolved resistance to various kinds of insecticide in the field. Reversion and selection, cross‐resistance, inheritance and mechanisms of abamectin resistance were characterised in a field‐derived multiresistant population of P. xylostella from China. RESULTS: Compared with a susceptible Roth strain, the field‐derived TH population showed ～5000‐fold resistance to abamectin. Rapid reversion of abamectin resistance was observed in the TH population when kept without insecticide selection. The TH‐Abm strain, selected from the TH population with abamectin, developed 23 670‐fold resistance to abamectin, a high level of cross‐resistance to emamectin benzoate and low levels of cross‐resistance to spinosad and fipronil. Genetic analyses indicated that abamectin resistance in the TH‐Abm strain was autosomal, incompletely dominant and polygenic. P450 monooxygenase activities in the TH‐Abm strain were significantly elevated compared with the TH strain. Piperonyl butoxide (PBO) inhibited a small part of abamectin resistance in the TH‐Abm strain. CONCLUSION: Field‐evolved high‐level resistance to abamectin in the TH population was not stable. Selection of the TH population with abamectin resulted in an extremely high level of cross‐resistance to emamectin benzoate and low levels of cross‐resistance to spinosad and fipronil. Enhanced oxidative metabolism was involved in, but may not be the major mechanism of, polygenic abamectin resistance in the TH‐Abm strain. Copyright © 2009 Society of Chemical Industry     

Pheromone‐based integrated pest management to control the diamondback moth Plutella xylostella in cabbage fields

Biorational and regular insecticide applications were evaluated for management of the diamondback moth (DBM) Plutella xylostella in cabbage (Brassica oleracea var capitata) in Karnataka State, India, in 1996 and 1997. The IPM programme, based on the pheromone trap catch threshold of eight moths per trap per night, included utilization of the parasitoid Cotesia plutellae. (250 000 adults ha⁻¹), the predator Chrysoperla carnea (2500 eggs ha⁻¹), the neem‐based chemical nimbecidine (625 ml ha⁻¹), the bacterium Bacillus thuringiensis (500 ml ha⁻¹), and the synthetic insecticide phosalone (2.8 litre ha⁻¹). The IPM programme induced a reduction of trap catches, egg and larval populations and, therefore, a low level of damage to the crop. The economic analysis showed that the cost of the IPM treatments was also considerably lower than that of ordinary insecticide practice (average of $62 relative to $123 ha⁻¹, respectively). Gross profit was also clearly higher in IPM plots than in farmer's fields, ranging from $777 to $810 ha⁻¹ in the IPM plots compared with $456 to $462 ha⁻¹ in the insecticide‐treated fields. As a consequence of lower input costs and higher gross profit, net profit in IPM treatments was even more favourable, and the economic savings associated with the utilization of the IPM programme amounted to $380 ha⁻¹ in 1996 and $410 ha⁻¹ in 1997. © 2000 Society of Chemical Industry     

Mode of inheritance and stability of resistance to Bacillus thuringiensis var kurstaki in a diamondback moth (Plutella xylostella) population from Malaysia

Genetic inheritance of resistance to Bacillus thuringiensis var kurstaki (BTK) was examined in a diamondback moth (Plutella xylostella) population collected from the Melaka region of Malaysia. A BTK‐selected sub‐population (BTK‐SEL) which was more than 100‐fold resistant to BTK compared with a susceptible (ROTH) population of P xylostella was used with standard reciprocal crosses and back‐crosses between ROTH and BTK‐SEL. Logit regression analysis of F ₁ reciprocal crosses indicated that BTK resistance was inherited as an incompletely recessive autosomal trait and controlled by a single locus. In contrast, other studies have shown that resistance to Cry1Ac is inherited as an incompletely dominant autosomal trait in a Cry1Ac‐selected sub‐population of the same Melaka population. The frequency of the allele responsible for resistance decreased without exposure to insecticide in the laboratory. © 2000 Society of Chemical Industry     

小菜蛾越冬生物学特性研究

研究了小菜蛾不同虫态的过冷却点,蛹的低温生存能力和越冬能力。小菜蛾的过冷却现象比较明显,蛹期过冷却点最低(-20.12℃),成虫次之(-16.56℃),幼虫期高(平均为-13.72℃),其中4龄幼虫过冷却点最高(-8.5℃)。表明在不同虫态中,蛹的抗低温能力最强。在-10、-5、0℃和5℃条件下,小菜蛾蛹的LT50、LT90、LT99.9随着温度的降低而缩短;蛹死亡99.9%需要的时间分别为10.29、21.68、27.77、41.39d,表明在冬季温度连续低于0℃时间超过28d的地区,小菜蛾不能越冬。连续两年冬天的埋蛹试验结果,蛹在北京4个地点的越冬死亡率均为100%。结合我国的气候区划分析,初步确定小菜蛾在北京地区野外不能越冬。