Toxicities and sublethal effects of seven neonicotinoid insecticides on survival, growth and reproduction of imidacloprid-resistant cotton aphid, Aphis gossypii

BACKGROUND: Imidacloprid has been a major neonicotinoid insecticide for controlling Aphis gossypii (Glover) (Homoptera: Aphididae) and other piercing–sucking pests. However, the resistance to imidacloprid has been recorded in many target insects. At the same time, cross‐resistance of imidacloprid and other insecticides, especially neonicotinoid insecticides, has been detected. RESULTS: Results showed that the level of cross‐resistance was different between imidacloprid and tested neonicotinoid insecticides (no cross‐resistance: dinotefuran, thiamethoxam and clothianidin; a 3.68–5.79‐fold cross‐resistance: acetamiprid, nitenpyram and thiacloprid). In the study of sublethal effects, imidacloprid at LC₂₀ doses could suppress weight gain and honeydew excretion, but showed no significant effects on longevity and fecundity of the imidacloprid‐resistant cotton aphid, A. gossypii. However, other neonicotinoid insecticides showed significant adverse effects on biological characteristics (body weight, honeydew excretion, longevity and fecundity) in the order of dinotefuran > thiamethoxam and clothianidin > nitenpyram > thiacloprid and acetamiprid. CONCLUSION: The results indicated that dinotefuran is the most effective insecticide for use against imidacloprid‐resistant A. gossypii. To avoid further resistance development, the use of nitenpyram, acetamiprid and thiacloprid should be avoided on imidacloprid‐resistant populations of A. gossypii. Copyright © 2011 Society of Chemical Industry     

长翅型与短翅型褐飞虱对杀虫剂的敏感性比较

采用稻苗浸渍法测定了长、短翅型褐飞虱对烯啶虫胺、环氧虫啶、呋虫胺、噻虫嗪、噻虫胺、吡虫啉、毒死蜱、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性,并对其体内解毒酶活力进行了比较分析。结果表明:长翅型与短翅型褐飞虱若虫对新烟碱类杀虫剂呋虫胺、噻虫嗪、噻虫胺和吡虫啉的敏感性存在显著差异,长翅型比短翅型更敏感;相反,对于有机磷类杀虫剂毒死蜱,短翅型褐飞虱则更敏感;2种生物型对烯啶虫胺、环氧虫啶、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性无显著差异。解毒酶相对比活力测定结果表明,长翅型褐飞虱若虫酯酶比活力显著高于短翅型,细胞色素P450单加氧酶比活力显著低于短翅型,而谷胱甘肽S-转移酶比活力无显著性差异。本研究结果可为褐飞虱的有效防控提供科学参考。     

Response of a red clone of Myzus persicae (Hemiptera: Aphididae) to sublethal concentrations of imidacloprid in the laboratory and greenhouse

BACKGROUND: Pest resurgence following a pesticide application may occur owing to a stimulatory (hormetic) response to sublethal insecticide concentrations. The objective of the present study was to examine the potential for a greenhouse‐derived red clone of Myzus persicae to exhibit resurgence owing to a hormetic response following a systemic imidacloprid treatment in a bell pepper greenhouse. RESULTS: No differences in mortality and fecundity were observed among apterous adults exposed to sublethal imidacloprid concentrations on excised pepper leaves fed aqueous solutions of imidacloprid. Survival of first‐generation progeny was negatively affected by imidacloprid exposure, yet surviving progeny exhibited no differences in development rates or fecundity from progeny of adults unexposed to imidacloprid. Aphid mortality declined most rapidly in clip cages on pepper leaves at the top of the pepper canopy as compared with leaves present at the middle or bottom of the pepper canopy. CONCLUSION: Imidacloprid decays rapidly in mature pepper plants, resulting in sublethal concentrations in the upper canopy in as little as 4 weeks. Sublethal insecticide concentrations have been implicated in the resurgence of pest populations; however, exposure to sublethal doses of imidacloprid are unlikely to result in pesticide‐induced resurgence of the M. persicae aphid clone examined in this study. Copyright © 2011 Society of Chemical Industry     

3种药剂对稻水象甲大田防治作用研究

本文开展了吡虫啉10%可湿性粉剂、阿维菌素2%乳油和三唑磷20%乳油等3种常见药剂对检疫性害虫稻水象甲的大田防治作用研究,试验结果表明,供试药剂对稻水象甲成虫均具有较好的防效,药后7d防效依次为94.58%、98.67%和100%。综合考虑,推荐阿维菌素2%乳油或吡虫啉10%可湿性粉剂为湖南防治稻水象甲的较理想药剂。     

拟水狼蛛对褐飞虱捕食功能反应及两者空间分布型

通过对湖南晚稻常规稻、杂交稻和超级杂交稻田的拟水狼蛛和褐飞虱进行调查,运用Taylor幂法和Iwao的回归分析法对拟水狼蛛、褐飞虱若虫及成虫的空间分布型拟合,两种方法研究结果表明:褐飞虱若虫、短翅型成虫和长翅型成虫在3个水稻品种上都为聚集分布,拟水狼蛛为随机分布。采用HollingⅡ型拟合拟水狼蛛对褐飞虱若虫、短翅型成虫和长翅型成虫的捕食功能,结果表明拟水狼蛛对三者捕食功能大小顺序为若虫长翅雄虫长翅雌虫短翅雄虫短翅雌虫,日最大捕食量分别为64.4、37.4、42.8、28.1头和35.1头。     

褐飞虱不同虫态的耐热性比较

温度是昆虫生长发育的重要影响因子之一。本研究以室内25℃、L∥D=16h∥8h、80%RH条件下终年饲养的褐飞虱1日龄初孵若虫、10日龄高龄(4~5龄)若虫、羽化1日龄短翅型和长翅型雌雄成虫为研究对象,采用持续升温和恒温相结合的方法,研究比较了褐飞虱各虫态耐热性。研究结果表明:长翅雄成虫对温度变化的适应能力较弱,耐热性差;短翅型雌成虫耐热性强;成虫的耐热性强于若虫。开展对昆虫的耐热性研究可为害虫的预测预报和防治提供重要的理论依据。     

Effect of fenvalerate on the reproduction and fitness costs of the brown planthopper, Nilaparvata lugens and its resistance mechanism

The brown planthopper (BPH), Nilaparvata lugens Stål, is a primary insect pest of cultivated rice, and its effective control is essential for crop production. However, in recent years, outbreaks of the brown planthopper have occurred more frequently in China. In order to determine the causes and mechanisms of insecticide-induced BPH resurgence and perform population management, we conducted the following studies. By the topical application method, our results showed that, fenvalerate acted as stimulus of fecundity from 3.50 × 10⁻³ to 2.02 × 10⁻² μg/female in the BPH. Apart from 7.00 × 10⁻³ μg/female, the number of hatched nymphs was increased gradually with an increase in application dose from 3.50 × 10⁻³ to 1.74 × 10⁻² μg/female. After continuous selection with fenvalerate for 11 generations by the rice-stem dipping method, a resistant strain was achieved with medium resistance to fenvalerate (RR 39.22). Life table study indicated that the resistant strain (G4 and G8) showed reproductive advantages, including increased female ratio, copulation rate and fecundity. But the hatchability of resistant strain was lower. The survival rate and emergence rate were significantly lower in G4 and G8 resistant strain. Resistant strains in G4 and G8 showed a fitness advantage (1.04 and 1.11), and the number of offspring in G8 generation was higher than that in G4 generation. The significant difference detected between resistant insects (G4, G5, G8 and G9) and S-strain contains not only the effect of resistant selection but also the effect of continuous rearing itself. Hence it was concluded that the BPH had the potential to develop high resistance against fenvalerate and the induction of the nymphs by sublethal doses of fenvalerate was of importance in the BPH population management, particularly in the predicting. Further studies demonstrated that triphenyl phosphate (TPP) and diethyl maleate (DEM) had no synergism on fenvalerate. However, piperonyl butoxide (PBO) displayed significant synergism in susceptible strain (1.97) and resistant strain (2.73). We concluded that esterase and glutathione S-transferase play little role in fenvalerate detoxification. The increase of the P450-monooxygenases detoxification is an important mechanism for fenvalerate resistance. Because their resistant populations had a fitness advantage, we should pay close attention to the occurrence of BPH and use other functionally different insecticides to control the BPH.     

烟粉虱细胞色素CYP6EM1基因的克隆及对吡虫啉抗性的作用

烟粉虱是一种世界性农业害虫,其防治手段以化学防治为主,新烟碱类杀虫剂吡虫啉常年用于防治烟粉虱,田间烟粉虱已经形成严重的抗药性。本研究通过分析烟粉虱吡虫啉抗性和敏感种群,发现细胞色素CYP6EM1基因在吡虫啉抗性品系中上调了4.7倍,进而克隆了其全长基因,进行了荧光定量PCR分析,发现该基因在吡虫啉抗性烟粉虱3龄若虫期和雄虫成虫期过量表达,并且在抗性成虫胸部和腹部过量表达。最后通过RNA干扰的方法使成虫的CYP6EM1基因表达量下降了54.8%,之后发现当烟粉虱暴露于吡虫啉时死亡率显著升高了39.65%,这表明CYP6EM1与烟粉虱对吡虫啉抗性的形成相关。研究结果对于揭示烟粉虱对吡虫啉产生抗性的机制有帮助,也为烟粉虱抗性水平田间监测及烟粉虱综合治理提供理论依据。     

Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

The effect of sublethal concentrations (LC₁ and LC₅₀) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC₁ and LC₅₀ concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC₅₀ values.     

Imidacloprid resistance and its mechanisms in field populations of brown planthopper, Nilaparvata lugens Stål in China

Imidacloprid is a key insecticide universally used for control of brown planthopper (BPH), and its resistance had been studied previously with laboratory selected strains. When the failure in field control happened in China in 2005, imidacloprid resistance in field populations of BPH (AQ, NJ, GL and WJ) was monitored and studied. The results demonstrated that the BPH of field populations had developed moderate to high level of resistance to imidacloprid. This resistance is attributed mainly to the enhanced P450 monooxygenases detoxification and could be enhanced in the same growing season if the insecticide was sprayed over and over. Further studies revealed that imidacloprid resistant hoppers did not show cross-resistance to all the neonicotinoid insecticides and high level of imidacloprid resistance in BPH was very unstable. Thus, efficient substitute neonicotinoids could be selected and “window control” could be implemented in resistance management. For checking the resistance mutation previously reported in laboratory selected strains, new corresponding target subunit genes were cloned and sequenced, but no mutations were found associated consistently with resistance.     

Comparative efficacy and economics of insecticides against chickpea semilooper,Autographa nigrisigna Walker (Noctuidae: Lepidoptera) infesting chickpea

Abstract

All fifteen insecticides tested significantly reduced pest levels. Permethrin 25 e.c. @ 150ga.i./ha proved significantly superior than other insecticides during both the years when observed 3 days after treatment but was at par with deltamethrin 2.8 e.c. and fenvalerate 20 e.c. when observed 7 and 15 days after spraying. Isofenphos was least effective, however, it did not differ significantly from phosalone during 1981–82 and fenitrothion, triazophos and phosalone during 1982–83. Maximum and the minimum cost benefit ratios of 1 : 10.6 and 1 : 4.0 were obtained in gamma BHC and fenvalerate treated plots respectively.     

Efficacy of systemic insecticides on the gall wasp Quadrastichus erythrinae in wiliwili trees (Erythrina spp.)

BACKGROUND: Erythrina gall wasp (EGW), Quadrastichus erythrinae Kim, was first found on Oahu Island, Hawaii, in April 2005. Its rapid spread and infestation in wiliwili trees (Erythrina spp.) have brought an urgent need to suppress its population. Little is known about the control of EGW in wiliwili trees.RESULTS: Among the systemic insecticides abamectin, dinotefuran and imidacloprid, applied via trunk injections or soil drenches, injections of imidacloprid showed better control of EGW in wiliwili trees. All the imidacloprid injection treatments had varying levels of effectiveness against EGW, but not the soil drench. The levels of imidacloprid were higher in lower canopies than those in the other parts within a tree. Imidacloprid remained detectable 1 year after treatment. The trees injected with the products IMA-jet and Merit 200 SL via Arborjet had lower infestation severity ratings for the entire growth season and carried more imidacloprid than those with Imicide via Mauget or Pointer via Wedgle injections.CONCLUSION: The results indicate that, among the three insecticides tested, imidacloprid is most effective against EGW in the trees. Concentrations of imidacloprid in the leaves need to be 4 mg kg(-1) or higher for good EGW control.     

吡虫啉防治香蕉黄胸蓟马的减量使用技术研究

为了降低吡虫啉在香蕉果实中的残留风险,探索减量使用方法,在香蕉蓟马防控窗口期,试验比较了70%吡虫啉水分散粒剂(WG)与9种低毒药剂对黄胸蓟马的防效,并进行了该吡虫啉制剂的不同稀释倍数及与不同药剂组合使用对蓟马的防治试验。结果表明：9种对比药剂中,22.4%螺虫乙酯悬浮剂(SC)3 000倍液,20%氟啶虫酰胺SC 2 000倍液和60 g/L乙基多杀菌素SC 1 500倍液的防效最好,达80%以上,与70%吡虫啉WG 3 000倍液的防效差异不显著。70%吡虫啉WG 5 000倍药液的防效为85.7%,与1 500倍药液和3 000倍药液的防效差异不显著,但显著高于7 000倍药液的防效。70%吡虫啉WG的5 000倍液分别与2.5%高效氯氟氰菊酯水乳剂(EW)的1 500倍液、60 g/L乙基多杀菌素SC的1 500倍液、25%噻虫嗪WG的2 000倍液和70%啶虫脒WG的5 000倍液组合使用,4种不同药剂组合处理的防效均达81.4%以上,与施用2次70%吡虫啉WG 5 000倍液的防效差异不显著。通过科学选择替换吡虫啉的药剂,合理使用70%吡虫啉WG的剂量,在香蕉蓟马防控窗口期...     

Antifeedant and sublethal effects of imidacloprid on Asian citrus psyllid,Diaphorina citri

BACKGROUND: Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, transmits the causal bacteria of the devastating citrus disease huanglongbing (HLB). Because of the variation in spatial and temporal uptake and systemic distribution of imidacloprid applied to citrus trees and its degradation over time in citrus trees, ACP adults and nymphs are exposed to concentrations that may not cause immediate mortality but rather sublethal effects. The objective of this laboratory study was to determine the effects of sublethal concentrations of imidacloprid on ACP life stages. RESULTS: Feeding by ACP adults and nymphs on plants treated daily with a sublethal concentration (0.1 µg mL^?1) of imidacloprid significantly decreased adult longevity (8 days), fecundity (33%) and fertility (6%), as well as nymph survival (12%) and developmental rate compared with untreated controls. The magnitude of these negative effects was directly related to exposure duration and concentration. Furthermore, ACP adults that fed on citrus leaves treated systemically with lethal and sublethal concentrations of imidacloprid excreted significantly less honeydew (7–94%) compared with controls in a concentration‐dependent manner suggesting antifeedant activity of imidacloprid. CONCLUSIONS: Sublethal concentrations of imidacloprid negatively affect development, reproduction, survival and longevity of ACP, which likely contributes to population reductions over time. Also, reduced feeding by ACP adults on plants treated with sublethal concentrations of imidacloprid may potentially decrease the capacity of ACP to successfully acquire and transmit the HLB causal pathogen. Copyright © 2009 Society of Chemical Industry     

Current status of the greenhouse whitefly, Trialeurodes vaporariorum, susceptibility to neonicotinoid and conventional insecticides on strawberries in southern California

Since 1998, the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), has emerged as a major insect pest of many horticultural crops in coastal California. Control of this pest has been heavily dependent upon chemical insecticides. Objectives of this study were to determine the status of the greenhouse whitefly susceptibility to neonicotinoid and conventional insecticides on strawberries in Oxnard/Ventura, a year-round intensive horticultural production area of southern California. For bioassay tests, adult whiteflies were collected from commercial strawberry crops, and immatures were directly developed from eggs laid by these adults. LD(50) values of soil-applied imidacloprid, thiamethoxam and dinotefuran were respectively 8.7, 3.2 and 4.9 times higher for the adults, 1.8, 1.2 and 1.5 times higher for the first-instar nymphs and 89.4, 390 and 10.4 times higher for the third-instar nymphs than their top label rates. LC(50) values of foliar-applied imidacloprid, thiamethoxam and acetamiprid were respectively 6.1, 6.0 and 1.7 times higher for the adults and 3.8, 8.7 and 4.4 times higher for the second-instar nymphs than their top label rates. For the adults, LC(90) values of endosulfan, malathion, methomyl, bifenthrin and fenpropathrin were 2.2, 1.2, 1.9, 2.3 and 4.9 times lower than their respective top label rates. Chlorpyrifos was not very effective against the adults, as indicated by its LC(90) being 120% higher than its top label rate. The present results strongly emphasize the need to develop resistance management strategies in the region.     

稻飞虱靶标杀虫剂亚致死剂量多代处理对两种赤眼蜂的影响

实验室条件下测定了四种稻飞虱杀虫剂吡虫啉、噻虫嗪、噻嗪酮和烯啶虫胺对稻螟赤眼蜂和螟黄赤眼蜂成蜂和蛹的毒性,以及亚致死剂量对两种赤眼蜂多代的影响。结果表明,四种杀虫剂对稻螟赤眼蜂成蜂中等风险;噻虫嗪对螟黄赤眼蜂成蜂中等风险,其他均安全。四种杀虫剂对两种赤眼蜂蛹均安全。亚致死剂量的噻虫嗪和烯啶虫胺处理可以刺激两种赤眼蜂的寄生力,该刺激作用并不会随着处理次数的增加而衰减。而吡虫啉和噻嗪酮显著降低螟黄赤眼蜂的寄生力,其中随着吡虫啉处理次数的增加,螟黄赤眼蜂的寄生力逐步降低。四种杀虫剂对子代羽化率无显著影响。四种杀虫剂对稻螟赤眼蜂的子代雌性比无显著影响;除吡虫啉外,在噻虫嗪、噻嗪酮和烯啶虫胺多代处理后,螟黄赤眼蜂的子代雌性比均有一定程度的下降。综上所述,如果在放蜂期间必须喷洒杀虫剂防治稻飞虱,建议要避开赤眼蜂成虫期,在放蜂4～6 d后优先选择噻嗪酮或烯啶虫胺。     

4种杀虫剂对玉米3种害虫的毒力及种子处理防治效果评价

为评价4种杀虫剂在玉米田防治灰飞虱Laodelphax striatellus、禾蓟马Frankliniella tenuicornis和玉米蚜Rhopalosiphum maidis的应用前景,采用浸苗法测定了其对3种害虫的毒力,并通过种子处理筛选对3种害虫田间防效较高的药剂。结果表明,噻虫嗪、呋虫胺和吡虫啉对灰飞虱、禾蓟马和玉米蚜具有较高毒力,LC50分别为0.14～1.10、4.24～31.01 mg/L和0.80～7.49 mg/L,氟啶虫酰胺的毒力最低,对3种害虫的LC50分别为84. 55、222.72 mg/L和44.81 mg/L。采用种子处理的方式施药后,各药剂处理组玉米出苗率与对照组无显著差异,安全性较高;播种后30 d,20%氟啶虫酰胺种子处理悬浮剂对灰飞虱、禾蓟马的防效均在75%以上,播种后40 d,70%噻虫嗪种子处理可分散粉剂对灰飞虱防效最高,其次为20%氟啶虫酰胺种子处理悬浮剂、8%呋虫胺悬浮种衣剂和600 g/L吡虫啉悬浮种衣剂;播种后50 d(玉米抽雄期)调查,20%氟啶虫酰胺种子处理悬浮剂对玉米蚜防治效果可达92.1%,表现出较高的防治效果,噻虫嗪、呋虫胺、吡虫啉防治效果略低,但均在70%以上,能有效防治玉米蚜的为害。综上,氟啶虫酰胺、噻虫嗪、呋虫胺和吡虫啉均适合用于防治玉米田灰飞虱、禾蓟马和玉米蚜3种害虫。     

Sublethal effect of Beauveria bassiana on feeding and fecundity of the sunn pest,Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

The sunn pest, Eurygaster integriceps Puton, is a major pest of wheat in West and Central Asia. Studies were conducted to investigate the effect of Beauveria bassiana (teleomorph; Cordyceps bassiana) isolates on the sunn pest. Bioassays were done with adult insects collected from overwintering sites at three different times. The effect of sublethal doses of fungi on the insects’ feeding and fecundity was determined. When the sunn pest adults were treated with 2 × 10⁷ conidia mL^?1, all isolates caused significant sunn pest mortality varying between 24 and 100% 12 days after inoculation. There were significant differences between mortality, depending on the date of fungal application. Adult sunn pests treated with B. bassiana at sublethal concentrations caused significantly less damage to wheat leaves than sunn pests in the control. The number of eggs laid by the sunn pest was significantly fewer when wheat plots in plastic greenhouse and field cages were infested with adult sunn pests treated at sublethal concentrations, compared with sunn pests in control plots. Results show that sublethal dosages of B. bassiana reduced sunn pest feeding and fecundity. Applying B. bassiana in sunn pest overwintering sites minimizes the pest populations, which would move to wheat fields in spring.     

Effect of seven new orchard pesticides on Galendromus occidentalis in laboratory studies

BACKGROUND: Biological control of phytophagous mites in orchards requires that pesticides used to manage other arthropod pests or diseases are harmless to predacious mites, as these are essential to keep phytophagous mites at non‐injurious population levels. This study evaluates the possible toxic attributes of acetamiprid, imidacloprid, thiacloprid, thiamethoxam, spirodiclofen, spinosad and methoxyfenoxide currently used in western Canadian orchards. RESULTS: None of these pesticides has any ovicidal properties against Galendromus occidentalis (Nesbitt). Imidacloprid and acetamiprid were highly toxic to the adults and reduced fecundity significantly. Thiamethoxam and spirodiclofen were non‐toxic to adults, but they slightly reduced fecundity. Thiacloprid, spinosad and methoxyfenoxide were harmless to adults and had no effect on fecundity. All compounds showed some repellence at 24 h intervals for 72 h. CONCLUSIONS: Imidacloprid and acetamiprid are incompatible with IPM programs because they are toxic to adults and negatively affect fecundity. Thiamethoxam and spirodiclofen need further field evaluation to determine if they are compatible with IPM programs because they slightly reduced fecundity. Thiacloprid, spinosad and methoxyfenoxide are harmless to adults, but they are slightly repellent. Therefore, with the exception of imidacloprid and acetamiprid, all these compounds should be field tested for compatibility in an IPM program. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri‐Food Canada. Published by John Wiley & Sons, Ltd