Pyrethroid resistance in Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and implications for its management in Australia

Abstract  The study was conducted to characterise the underlying resistance mechanisms responsible for high levels of pyrethroid resistance in Frankliniella occidentalis (Pergande) in Australia. Seven commercially available pyrethroids (acrinathrin, alpha-cypermethrin, bifenthrin, deltamethrin, esfenvalerate, permethrin and tau-fluvalinate) were evaluated against seven F. occidentalis strains collected from ornamentals, fruit and vegetables in three states of Australia. A Potter spray tower was used to test for pyrethroid resistance and all field strains were found to be resistant, with resistance ratios ranging from 15-fold deltamethrin to 1300-fold tau-fluvalinate. The two most resistant strains were further tested for detoxification enzymes that could be involved in resistance. Three synergists, piperonyl butoxide (PBO), diethyl maleate (DEM) and profenofos, which, respectively, inhibit the enzymes cytochrome P-450 monooxygenases, glutathione S -transferases and esterases, were used. The synergism data indicate that multiple mechanisms may be involved in pyrethroid resistance in Australian populations of F. occidentalis . Among the three synergists, PBO considerably reduced pyrethroid resistance in the selected strains compared with DEM and profenofos. The practical implication for PBO use to suppress pyrethroid resistance in F. occidentalis is elaborated.     

Monitoring insecticide resistance in Australian Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) detects fipronil and spinosad resistance

Abstract  Insecticide resistance monitoring using a Potter precision spray tower with discriminating concentration and log dose probability techniques underpins the Australian insecticide management strategy for Frankliniella occidentalis Pergande. Abamectin, acephate, chlorpyrifos, dichlorvos, dimethoate, endosulfan, fipronil, malathion, methamidophos methidathion, methiocarb, methomyl, pyrazophos and spinosad are recommended for use against F. occidentalis but abamectin, methiocarb and pyrazophos are the only chemicals where insecticide resistance has not been detected. Although not registered, chlorfenapyr was effective against F. occidentalis and should be pursued for that purpose. In contrast, chlorpyrifos, dichlorvos and malathion resistance were detected at low to moderate levels throughout the study period putting their sustainable use for F. occidentalis control in doubt . Although it appears that acephate, dimethoate, endosulfan, fipronil, methamidophos, methidathion and spinosad remain effective, some populations contained a small percentage of thrips that survived exposure to a concentration that killed 100% of the susceptible strain. Subsequent laboratory selection of one such population separately with fipronil and spinosad caused an increase in resistance to these insecticides. These products must now be considered at risk. This is the first report of fipronil or spinosad resistance in populations of F. occidentalis.     

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) chemical control: residues associated with the three consecutive spray strategy

Abstract  Chemical control of western flower thrips Frankliniella occidentalis requires three consecutive applications of the same pesticide, 3–6 days apart. Initially, pesticides recommended for western flower thrips control were based on established maximum residue limits (MRLs) from previously established use on pests other than F. occidentalis , rather than product efficacy against F. occidentalis . Moreover, MRLs were based on a single application rather than three consecutive sprays. Chemical residues associated with the three-spray strategy were not quantified. Here those residues are quantified and the scope for rate increases is further tested, as laboratory bioassays suggest that some current permit rates may be too low to be effective. At established withholding periods (WHPs), current permit rate applications of abamectin (0.018 g/L) on strawberry and tomato, and methidathion (0.5 g/L) and endosulfan (0.666 g/L) on lettuce produced residues above the current Australian MRL. Results indicated that a higher than the current permit rate for endosulfan (2.0 g/L) could be sustained on cucumber and strawberry at established WHPs, but would require an extension to the current WHP. Similarly, a modest increase in methidathion (1.0 g/L) rate on tomato could be practical, again with a WHP extension. In each instance additional supporting data are required to accurately quantify the proposed WHP extensions.     

Mechanisms of resistance to spinosad in the western flower thrip, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Cross‐resistance, resistance mechanisms, and mode of inheritance of spinosad resistance were studied in the western flower thrip, Frankliniella occidentalis (Pergande). Spinosad (naturalyte insecticide) showed low cross‐resistance to prothiophos (organophosphorus insecticide) and chlorphenapyr (respiratory inhibitor) showed some cross‐resistance to thiocyclam (nereistoxin). The synergists PBO (piperonyl butoxide), DEM (diethyl maleate), and DEF (s, s, s‐tributyl phosphorotrithioate) did not show any synergism on the toxicity of spinosad in the resistant strain (ICS), indicating that metabolic‐mediated detoxification was not responsible for the spinosad resistance, suggesting that spinosad may reduce sensitivity of the target site: the nicotinic acetylcholine receptor and GABA receptor. Following reciprocal crosses, dose‐response lines and dominance ratios indicated that spinosad resistance was incompletely dominant and there were no maternal effects. The results of backcross showed that spinosad resistance did not fit a single‐gene hypothesis, suggesting that resistance was influenced by several genes.     

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) chemical control: insecticide efficacy associated with the three consecutive spray strategy

Abstract  After the initial 1993 discovery of Frankliniella occidentalis , western flower thrips, in Australia, temporary chemical control permits were issued to facilitate their insecticidal control. However, these permits were based on established endemic pests of Australian horticulture rather than demonstrated efficacy against F. occidentalis , and laboratory bioassays of Australian field-collected F. occidentalis suggested that some permit application rates were too low to be effective. In 2002 and 2003 field-based trials were carried out in strawberry and lettuce to collect field-generated efficacy data to verify the laboratory conclusions. It was found that by increasing field application rates above the existing permit rate, efficacy was increased, but not for all insecticides and not for all thrips life stages. Increasing the rate of abamectin and endosulfan in strawberry increased control of adults and larvae and increasing the rate of endosulfan in lettuce increased efficacy against larvae only. Spinosad was effective at both rates tested in strawberry, suggesting that the current permit rate could be reduced. The ability to use reduced rates may be useful if used in combination with Integrated Pest Management programs.     

The spread of the western flower thrips Frankliniella occidentalis (Pergande)

Abstract 1 Since the late 1970s, the western flower thrips has spread from its original distribution in western North America to become a major worldwide crop pest. 2 A wide range of data sources have been used to map the original distribution in the U.S.A. and Canada, and the progress of the spread in the U.S.A., Canada, Europe, northern Africa and Australia. 3 The possible reasons for the start of the spread are discussed. The most likely reason is that intensive insecticide use in horticulture in the 1970s and 1980s selected an insecticide resistant strain or strains. These then established in glasshouses across North America and spread from there to Europe, Asia, Africa and Australia. 4 The international spread of the western flower thrips occurred predominantly by the movement of horticultural material, such as cuttings, seedlings and potted plants. Within Europe, an outward spread from the original outbreak in the Netherlands is discernible. The speed of spread was 229 ± 20 km/year. 5 The spread has not been restricted to glasshouses. The western flower thrips has established outdoors in areas with milder winters; for example, across the southern U.S.A., southern Europe and Australia. It also overwinters in some regions with colder winters. 6 Polyphagous phytophagous thrips have many factors predisposing them to become worldwide crop pests, particularly in glasshouses. Some other species that might spread in a similar way to the western flower thrips are listed.     

Insecticide resistance in Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) collected from horticulture and cotton in Turkey

Abstract  The sensitivity of three reference strains of the western flower thrips Frankliniella occidentalis from Australia, Israel and Turkey was evaluated and their response did not differ significantly and so they are considered typical of susceptible F. occidentalis . Field strains of F. occidentalis from Antalya, Turkey were tested for resistance against five classes of insecticide during the years 2001–2003. Difference in the field strains response to abamectin, endosulfan, malathion and methomyl was low (<3.0-fold) and in many cases not significant. However, all strains were likely resistant to cypermethrin (1.6- to 12.2-fold at LC₅₀ (lethal concentration)). The established agricultural practices and ecosystem patterns in the Antalya province are assumed to contribute to delay in insecticide resistance in F. occidentalis .     

Biotic resistance limits the invasiveness of the western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae), in Florida

The spread of the western flower thrips, Frankliniella occidentalis (Pergande), has resulted in the world‐wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. (Hemiptera: Anthocoridae) are effective predators that suppress populations of thrips on crop and non‐crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, F. tritici (Fitch) and F. bispinosa (Morgan). The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad‐spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species.     

Genetics of spinosad resistance in Frankliniella occidentalis (Thysanoptera: Thripidae)

The genetic basis of spinosad resistance was investigated in the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). The resistant strain, selected in the laboratory for spinosad resistance from a pool of thrips populations collected in Almeria (southeastern Spain), showed a very high resistance to spinosad (356,547-fold based on LC50 values) compared with the laboratory susceptible strain. Mortality data from reciprocal crosses of resistant and susceptible thrips indicated that resistance was autosomal and not influenced by maternal effects. Analysis of probit lines from the parental strains and reciprocal crosses showed that resistance was expressed as an almost completely recessive trait. To determine the number of genes involved, a direct test of monogenic inheritance based on the backcrosses suggested that resistance to spinosad was probably controlled by one locus. Another approach, which was based on phenotypic variances, showed that nE, or the minimum number of freely segregating genetic factors for the resistant strain, equaled 0.59.     

Biological control of the western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in glasshouse sweet peppers with Orius spp. (Hemiptera: Anthocoridae). A comparative study between O. niger (Wolff) and O. insidiosus (Say)

In a comparative study for biocontrol of the western flower thrips (WFT) in commercial sweet peppers Orius spp. effectively controlled WFT. The introduced native Orius niger had replaced the introduced imported Orius insidiosus by the end of the growing season.     

Life‐cycle variation,including female production by virgin females in Frankliniella occidentalis (Thysanoptera: Thripidae)

The influence of three different temperatures on developmental time and sex ratio was investigated in the bisexual Thysanoptera species Frankliniella occidentalis. Increasing temperatures decreased developmental time and induced a more female biased sex ratio. Remarkably, there are second instars with a prolonged developmental time requiring the same number of hours as the shortest developmental time from egg to adult. Arrhenotokous reproduction in this species is based on haplodiploidy, with virgin females producing male offspring exclusively. However, at all three temperatures tested, about 0.5% of offspring from unfertilized eggs were females. The presence of Wolbachia could not be detected in Western flower thrips and can be excluded as influencing reproduction in this species.     

Biology of Thripinema nicklewoodi (Tylenchida), an Obligate Frankliniella occidentalis (Thysanoptera) Parasite

Frankliniella occidentalis, a serious pest of agricultural crops, is difficult to manage because chemical and biological control measures frequently fail to affect F. occidentalis in their preferred microhabitats. Parasitism by the host-specific, entomopathogenic nematode Thripinema nicklewoodi may provide a much-needed alternative to current control strategies. Infection does not cause death of the host; rather, the result is sterilization that leads to suppression of F. occidentalis populations. We describe a simple rearing method and the results from studies aimed at providing details on its biology-both essential first steps to examining its biological control potential. All F. occidentalis life stages are susceptible to infection, but to varying degrees (most susceptible to least susceptible): female pupae, second instar larvae, first instar larvae, male pupae, adult females, adult males. Nematodes emerge from female and male F. occidentalis for approximately 15 and 9 days, with approximately 14 and 7 nematodes emerging per day, respectively. Females and males are short-lived outside of the host, with mean survival rates ranging between 7 and 86 hours. Transmission does not occur in the soil but rather on or within plant structures that are preferred microhabitats visited by F. occidentalis. Results from a dose-response study suggest that augmentative applications of T. nicklewoodi may be useful to generate increased infection rates and subsequent suppression of F. occidentalis populations.     

入侵害虫西花蓟马及其他8种常见蓟马的分子鉴定

用PCR产物直接测序法对入侵害虫西花蓟马和其他8种蓟马的线粒体 COⅠ基因433 bp片段测序，获得62个个体的序列。分子数据分析显示： 种内个体间平均遗传距离在0～0.005之间，2003年在北京发现的西花蓟马与欧洲等地区报导的西花蓟马不存在明显的遗传差异； 9种蓟马种间平均遗传距离为0.213。构建的NJ树可以很好的显示蓟马的聚类，物种各单元型最初分支自展值均达到100%。结果表明，基于PCR及直接测序技术的分子鉴定可以达到准确鉴定蓟马物种之目的。     

Management of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in hydroponic strawberry crops: using yellow sticky traps to determine action thresholds

Abstract  The relationship between western flower thrips (WFT) populations in flowers and catches on yellow sticky traps was investigated in a hydroponic strawberry crop in the Sydney area in 1999–2000. The thrips population was initially dominated by males, but by mid-summer it was composed primarily of females. At a point when approximately 60–65% of WFT on traps were female (approximately 20–30 females per trap), the overall density of thrips on traps and in the crop increased rapidly, resulting in severe damage to immature fruit. The sex ratio of 0.60–0.65 females corresponded very closely to a mean of five adult WFT per flower at the start of the trapping week, which was an infestation level previously calculated as the action threshold to prevent damage to young green fruit.     

Mechanisms associated with methiocarb resistance in Frankliniella occidentalis (Thysanoptera: Thripidae)

Biochemical mechanisms associated with methiocarb resistance were examined in laboratory-selected and field populations of the western flower thrips, Frankliniella occidentalis (Pergande). Seven populations were examined and they differed in their susceptibility to methiocarb by 30 times. Including the synergists piperonyl butoxide, a cytochrome P-450 monooxygenase inhibitor, or S,S,S-tributylphosphorotrithioate, an esterase inhibitor, in the methiocarb bioassays partially suppressed resistance in the most resistant populations. In vitro assays of general esterase, glutathione S-transferase, and acetylcholinesterase activities showed increased activity in some of the resistant populations and increased activity of the enzymes after methiocarb selection on one of the populations. Assays of acetylcholinesterase sensitivity to inhibition by methiocarb, dichlorvos, and eserine suggested insensitive acetylcholinesterase in two of the resistant populations. These results indicate that methiocarb resistance in F. occidentalis was polyfactorial and involved detoxification and altered target site. None of the biochemical assays showed interpopulation enzymatic differences strongly correlated with the level of methiocarb resistance. The possibilities for developing rapid biochemical diagnostic assays to detect methiocarb resistance in F. occidentalis are discussed.     

The ultrastructure of Malpighian tubules and hindgut of Frankliniella occidentalis (Pergande) (Thysanoptera : Thripidae)

The ultrastructure of the western flower thrips, Frankliniella occidentalis (Pergande) (Order : Thysanoptera), has 4 Malpighian tubules that are free of the intestine as they leave their junction at the pyloric region. The tubules consist of an epithelium with a single type of microvillated cells; proximally, the cells are lined by a thin cuticle. Numerous mitochondria, basal infoldings of the plasma membrane and vesicles with varying densities suggest active transit of fluid in the cell for osmoregulation. Two of the Malpighian tubules are bent posteriorly and closely adhere to the hindgut in the region of the rectal pads where the 2 epithelia are separated only by a basal lamina. The ultrastructure of this region suggests possible fluid reabsorption from the gut lumen.     

Rapid diagnosis of the invasive species,Frankliniella occidentalis (Pergande): a species‐specific COI marker

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an invasive species and currently occurs in only a few areas in China. An easy, accurate and developmental‐stage independent method to identify F. occidentalis would be a valuable tool to facilitate pest management decision making and, more importantly, to provide an early warning so actions can be taken to prevent its introduction into non‐infested areas. Morphological identification of thrips adults and, to a lesser extent, of second‐stage larvae is the main method currently available to identify F. occidentalis. Molecular identification, however, can be easily carried out by a non‐thrips‐specialist with a little training. In this study, DNA sequence data [within the mitochondrial cytochrome oxidase I gene (COI)] and polymerase chain reaction (PCR) were utilized to develop a molecular diagnostic marker for F. occidentalis. A primer set and PCR cycling parameters were designed for the amplification of a single marker fragment (340 bp) of F. occidentalis COI mtDNA. Specificity tests performed on 28 thrips species, efficacy tests performed on five immature developmental stages as well as on male and female adults and tests on primer sensitivity all demonstrated the diagnostic utility of this marker. Furthermore, the primer set was tested on seventeen F. occidentalis populations from different countries and invaded areas in China and proved to be applicable for all geographic populations. It was used successfully to clarify the distribution of F. occidentalis in the Beijing metro area. These results suggested that this diagnostic PCR assay provides a quick, simple and reliable molecular technique for the identification of F. occidentalis.     

入侵昆虫西花蓟马的潜在适生区分析

本文在分析西花蓟马生物学特性及其世界分布的基础上,采用CLIMEX软件及提供的气候匹配性分析和位置比较分析两种分析模型,结合我国634个气象站点的数据,预测西花蓟马在我国的潜在分布区。结果表明,西花蓟马在生态气候指数EI≥3的地区爆发危害风险性较大。西花蓟马在我国的广东、海南、安徽、福建、江苏、山东、广西、贵州、河南、湖北、陕西、四川、云南、重庆等省市具有广泛的适生区; 其适宜生存的北界分布在中国年平均温度10℃等温线、1月份平均温度-8℃等温线以及年平均极端最低温度-20℃等温线附近; 而新疆、青海、西藏、黑龙江、吉林、辽宁、内蒙古等省或自治区为不适应生存区。     

寄主植物接种番茄斑萎病毒对西花蓟马种群的影响

【目的】西花蓟马Frankliniella occidentalis (Pergande)是一种入侵我国的重要害虫, 而番茄斑萎病毒是以西花蓟马传播为主的一种极具危害性的世界性病毒, 通过研究西花蓟马与番茄斑萎病毒之间的互作将有助于进一步深入理解西花蓟马以及番茄斑萎病毒的发生与猖獗机制, 同时也将为制定合理、可持续的控制西花蓟马及其传播的植物病毒防控策略提供理论依据。【方法】利用应用特定年龄-龄期及两性生命表方法, 研究了西花蓟马在辣椒3种处理（健康CK、机械损伤MD、机械接种番茄斑萎病毒MI）叶片上的生长发育、存活及种群增长。【结果】健康、机械损伤和机械接毒叶片上的发育历期依次为12.45, 11.97和11.18 d。雌雄成虫寿命和雌虫产卵量在不同处理植株叶片上差异显著(P<0.05), 在机械接毒叶片上寿命最长(雌13.51 d, 雄12.69 d); 繁殖能力最强, 产子代数高达33.01头1龄若虫/雌。健康、机械损伤和机械接毒叶片上西花蓟马内禀增长率分别为-0.009, 0.153和0.190 d-1, 净生殖率依次为0.84, 14.54和21.79。【结论】番茄斑萎病毒诱导寄主植物辣椒反应使西花蓟马发育历期缩短, 成虫寿命延长, 繁殖能力提高, 种群增长加速。