Thiamethoxam acts as a target‐site synergist of spinosad in resistant strains of Frankliniella occidentalis

BACKGROUND: Previous studies have suggested that the resistance mechanism towards spinosad in Frankliniella occidentalis (Pergande) is an altered target site. Like the neonicotinoids, the spinosyns act on nicotinic acetylcholine receptors (nAChRs) in insects, but at a distinct site. The changes in nAChRs related to spinosad resistance in thrips might involve interaction with neonicotinoids. In this study, the efficacy of spinosad and neonicotinoids, alone and in combination, was evaluated in susceptible and spinosad‐resistant thrips strains. RESULTS: The neonicotinoids tested were imidacloprid, thiacloprid, acetamiprid, thiamethoxam and clothianidin. No cross‐resistance was shown between spinosad and any of the neonicotinoids. However, an increased toxicity was observed when a mixture of spinosad with thiamethoxam or clothianidin was tested. No synergism was found in the susceptible strains. The more spinosad‐resistant the thrips strain, the stronger was the synergism. CONCLUSION: Data suggest that spinosad and thiamethoxam may interact at the nAChRs in spinosad‐resistant thrips, facilitating enhanced insecticidal action. Copyright © 2012 Society of Chemical Industry     

Automatic sex detection of individuals of Ceratitis capitata by means of computer vision in a biofactory

BACKGROUND: The sterile insect technique (SIT) is acknowledged around the world as an effective method for biological pest control of Ceratitis capitata (Wiedemann). Sterile insects are produced in biofactories where one key issue is the selection of the progenitors that have to transmit specific genetic characteristics. Recombinant individuals must be removed as this colony is renewed. Nowadays, this task is performed manually, in a process that is extremely slow, painstaking and labour intensive, in which the sex of individuals must be identified. The paper explores the possibility of using vision sensors and pattern recognition algorithms for automated detection of recombinants. RESULTS: An automatic system is proposed and tested to inspect individual specimens of C. capitata using machine vision. It includes a backlighting system and image processing algorithms for determining the sex of live flies in five high-resolution images of each insect. The system is capable of identifying the sex of the flies by means of a program that analyses the contour of the abdomen, using fast Fourier transform features, to detect the presence of the ovipositor. Moreover, it can find the characteristic spatulate setae of males. Simulation tests with 1000 insects (5000 images) had 100% success in identifying male flies, with an error rate of 0.6% for female flies. CONCLUSION: This work establishes the basis for building a machine for the automatic detection and removal of recombinant individuals in the selection of progenitors for biofactories, which would have huge benefits for SIT around the globe.     

Efficacy of lufenuron as chemosterilant against Ceratitis capitata in field trials

Two field trials in citrus orchards in Turis (Valencia, Spain) and Denia (Alicante, Spain) were performed in order to test the sterilant effect of the insect growth regulator lufenuron against wild medfly Ceratitis capitata (Wiedemann) populations. Two application methods for lufenuron were tested: spraying, in spots, an emulsion of lufenuron in a protein bait, and hanging delta traps that contained a proteinaceous gel with lufenuron (solid bait). The sterilant effect was measured as medfly population reduction, reduction of fruit damage in treated fields, and the number of eggs hatching in punctured fruits. In order to assess the efficacy of lufenuron treatments, we recorded results obtained from two different zones in both trial fields: an outer zone, close to untreated fields, and an inner zone, in the centre of lufenuron treated fields. We observed a minimum sterilant effect in the outer zone and a maximum sterilant effect in the inner one. The maximum sterilant effect was in the inner zone, where a reduction of medfly population of 80.4% in the sprayed field and a reduction of 77.6% in the solid bait field was observed. In addition, the greater the distance from the untreated zones of the treated orchard (inwards), the lower the fruit damage and medfly population level. In this inner zone, fruit punctured by medfly developed significantly fewer larvae (38.8%) than punctured fruits from the outer zone (68.6%). In addition, we recorded the decline in the activity of the lufenuron treatments with time. Lufenuron activity persisted in field for at least 2 weeks with spray applications, and for 3 months with bait gels.     

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.     

Spatial regression analysis of Ceratitis capitata Wiedemann (Diptera: Tephritidae) on Terceira Island,Azores

The fruit fly Ceratitis capitata Wiedemann is one of the most important threats to the trade of fresh fruits in the world due to its ability to survive in a wide range of hosts and climatic conditions. The main goal of this study is to evaluate if there is any significant relationship between the abundance of wild adults of C. capitata and the spatial characteristics of the location. The ordinary least squares estimation model calculated for each gender cannot provide a satisfactory general explanation for abundance of both genders of wild adults, yet it might generate some hypotheses about wild adult females of C. capitata fruit-seeking behaviour. Results from geographically weighted regression analysis can provide a satisfactory general explanation for abundance of both genders of wild adults. Both methods suggest that males are more dispersed than females, and because of that they might play an important role in scouting the surroundings for additional fruit hosts. The presence of some host-plants, even in places offering less protection (like pasture areas), provides an ecological corridor that supports the spread of wild adults of C. capitata.     

Beet armyworm (Spodoptera exigua) resistance to spinosad

Susceptibility to spinosad (Success®/Tracer®) of beet armyworm (Spodoptera exigua) from the southern USA and Southeast Asia was determined through exposure of second‐ and third‐instar larvae to dipped cotton leaves. LC₅₀ estimates of susceptibility of second‐ and third‐instar larvae of field populations ranged from 0.279 to 6.14 and 0.589 to 14.0 mg spinosad litre⁻¹, respectively. A Thailand population was 22‐ and 24‐fold less susceptible than the six other US field populations evaluated, and 85‐ and 58‐fold less susceptible than a reference laboratory population, respectively. From these results, we initiated experiments to test the hypothesis that the Thailand population was resistant to spinosad. F₁ crosses between the resistant Thailand population and a susceptible reference strain yielded individuals that were 22‐fold less sensitive to spinosad than the susceptible parent. This same resistant strain exhibited significantly greater survivorship on plants treated with spinosad in the field. Lastly, selection of an Arizona population resulted in a significant reduction in susceptibility to spinosad, further substantiating the hypothesis of a genetic basis for resistance to spinosad. These findings indicate a vulnerability of this new insecticide to resistance development in beet armyworm and should serve as a warning against excessive use of it. © 2000 Society of Chemical Industry     

Genetics of spinosad resistance in a multi-resistant field-selected population of Plutella xylostella

Resistance to the bacteria-derived insecticides spinosad (Conserve), abamectin (Vertimec), Bacillus thuringiensis var kurstaki (Btk) (Dipel), B thuringiensis var aizawai (Bta) (Xentari), B thuringiensis crystal endotoxins Cry1Ac and Cry1Ca, and to the synthetic insecticide fipronil was estimated in a freshly-collected field population (CH1 strain) of Plutella xylostella (L) from the Cameron Highlands, Malaysia. Laboratory bioassays at G1 indicated significant levels of resistance to spinosad, abamectin, Cry1Ac, Btk, Cry1Ca, fipronil and Bta when compared with a laboratory insecticide-susceptible population. Logit regression analysis of F1 reciprocal crosses indicated that resistance to spinosad in the CH1 population was inherited as a co-dominant trait. At the highest dose of spinosad tested, resistance was close to completely recessive, while at the lowest dose it was incompletely dominant. A direct test of monogenic inheritance based on a back-cross of F1 progeny with CH1 suggested that resistance to spinosad was controlled by a single locus.     

Western flower thrips resistance to insecticides: detection, mechanisms and management strategies

Insecticide resistance continues to be one of the most important issues facing agricultural production. The challenges in insecticide resistance and its management are exemplified by the situation with the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). This highly invasive pest has a great propensity for developing insecticide resistance because of its biological attributes, and cases of resistance to most classes of insecticides used for its management have been detected. To combat insecticide resistance in the western flower thrips, several insecticide resistance management (IRM) programs have been developed around the world, and these are discussed. Successful programs rely on non-insecticidal tactics, such as biological and cultural controls and host plant resistance, to reduce population pressures, rotations among insecticides of different mode of action classes to conserve insecticide efficacy, resistance monitoring, sampling to determine the need for insecticide applications and education to assure proper implementation. More judicious insecticide use is possible with the development of well-founded economic thresholds for more cropping systems. While growers will continue to rely on insecticides as part of western-flower-thrips- and thrips-transmitted virus management, more effective management of these pests will be achieved by considering their management in the context of overall integrated pest management, with IRM being a key component of those comprehensive programs.     

Insecticide resistance,control failure likelihood and the First Law of Geography

Insecticide resistance is a broadly recognized ecological backlash resulting from insecticide use and is widely reported among arthropod pest species with well‐recognized underlying mechanisms and consequences. Nonetheless, insecticide resistance is the subject of evolving conceptual views that introduces a different concept useful if recognized in its own right – the risk or likelihood of control failure. Here we suggest an experimental approach to assess the likelihood of control failure of an insecticide allowing for consistent decision‐making regarding management of insecticide resistance. We also challenge the current emphasis on limited spatial sampling of arthropod populations for resistance diagnosis in favor of comprehensive spatial sampling. This necessarily requires larger population sampling – aiming to use spatial analysis in area‐wide surveys – to recognize focal points of insecticide resistance and/or control failure that will better direct management efforts. The continuous geographical scale of such surveys will depend on the arthropod pest species, the pattern of insecticide use and many other potential factors. Regardless, distance dependence among sampling sites should still hold, following the maxim that the closer two things are, the more they resemble each other, which is the basis of Tobler's First Law of Geography. © 2016 Society of Chemical Industry     

新烟碱类杀虫剂抗药性研究进展

新烟碱类杀虫剂是一类新开发的杀虫剂。研究表明，害虫野外种群对其敏感性差弄较大，现已有多种害虫对吡虫啉和啶虫脒产生了抗性。初步研究显示，马铃薯叶甲对吡虫啉抗性以不完全隐性的常染色体遗传；抗性似不稳定，交互抗性谱随虫种而变化，抗性形成可能与多功能氧化酶和酯酶有关。合理轮用和高剂量杀死策略是治理其抗性的有效措施。     

蔬菜蚜虫抗药性现状及抗性治理策略

蚜虫是为害蔬菜作物的一类重要害虫,如不防治会给蔬菜生产造成重大经济损失。长期以来主要依靠使用农药防治蔬菜蚜虫,但由于化学农药的不合理使用,蔬菜蚜虫对有机磷、拟除虫菊酯、氨基甲酸酯、新烟碱等多种类型的杀虫药剂均产生了不同程度的抗性。本文对常见的蔬菜蚜虫的抗药性现状、抗药性机理以及治理策略进行了论述,以期为该类害虫的可持续控制提供参考。     

灰飞虱对杀虫剂抗药性的研究进展

灰飞虱对杀虫剂产生抗药性是其近年来暴发频繁的重要原因。本文综述了国内外关于灰飞虱抗药性的研究成果,包括灰飞虱抗药性的发展、交互抗性、抗性机理、抗性遗传及生物适合度等。田间灰飞虱种群对多种药剂产生了不同程度的抗药性,其中对新烟碱类药剂吡虫啉和昆虫生长调节剂噻嗪酮产生了高水平到极高水平抗性(抗药性倍数分别为44.6～108.8倍和超过200倍),对有机磷类药剂毒死蜱和乙酰甲胺磷(抗药性倍数分别为10～12.6倍和9～13倍)、氨基甲酸酯类药剂甲萘威和残杀威(抗药性倍数分别为29.8～45.3倍和40.1～131.5倍)和拟除虫菊酯类药剂高效氯氰菊酯和溴氰菊酯(抗药性倍数分别为7.8～108.8倍和12～21倍)产生了中等水平到高水平的抗药性,对氟虫腈、阿维菌素和噻虫嗪没有产生抗药性(抗性倍数5倍)。长期大面积使用化学药剂是灰飞虱产生抗药性的重要原因。因此,必须加强灰飞虱的抗性治理,以延缓其抗药性进一步发展。     

Insecticide resistance in disease vectors of public health importance

Vector-borne diseases are a global problem--a trend that may only increase if global temperature rises and demographic trends continue--and their economic and social impact are enormous. Insecticides play a vital role in the fight against these diseases by controlling the vectors themselves in order to improve public health; however, resistance to commonly used insecticides is on the rise. This perspective outlines the major classes of disease vector control agents and the mechanisms of resistance that have evolved, arguing that effective resistance management strategies must carefully monitor resistance in field populations and use combinations of the limited modes of action available to best effect. Moreover, the development of novel insecticide classes for control of adult mosquitoes and other vectors becomes increasingly important.