Inheritance of resistance to acrinathrin in Frankliniella occidentalis (Thysanoptera: Thripidae)

BACKGROUND: The western flower thrips (WFT), Frankliniella occidentalis (Pergande), is an economically important pest. The genetic basis of acrinathrin resistance was investigated in WFT. RESULTS: The resistant strain, selected in the laboratory for acrinathrin resistance from a pool of thrips populations collected in Almeria (south-eastern Spain), showed a high resistance to acrinathrin (43-fold based on LC(50) 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 a codominant trait. To determine the number of genes involved, a direct test of monogenic inheritance based on the backcrosses suggested that resistance to acrinathrin was probably controlled by one locus. Another approach, which was based on phenotypic variances, showed n(E), or the minimum number of freely segregating genetic factors for the resistant strain, to be 0.79. CONCLUSION: The results showed that acrinathrin resistance in WFT was autosomal and not influenced by maternal effects, and was expressed as a codominant trait, probably controlled by one locus.     

Effect of Bacillus thuringiensis subsp. israelensis and neonicotinoid insecticides on the fungus gnat Bradysia sp nr. coprophila (Lintner) (Diptera: Sciaridae)

The soil bacterium Bacillus thuringiensis Berliner subsp. israelensis (Bti), the neonicotinoid insecticides dinotefuran, imidacloprid, thiamethoxam and clothianidin and the insect growth regulator pyriproxyfen were evaluated to determine their efficacy against the larval stages of the fungus gnat Bradysia sp nr. coprophila (Lintner) in the laboratory. Treatments were applied as a drench to the growing medium in polypropylene deli containers. The Bti treatments had no effect on either instar tested, whereas all the other compounds negatively affected both the second and third instars. This study demonstrates that the soil bacterium B. thuringiensis var. israelensis may not be active on these larval stages, whereas the neonicotinoid insecticides and the insect growth regulator pyriproxyfen are effective on these stages. The fact that Bti is not effective on the second and third instars of the fungus gnat means that greenhouse producers using this insecticide must make applications before fungus gnat populations build up and before overlapping generations develop.     

Effectiveness of insecticide-treated and non-treated trap plants for the management of Frankliniella occidentalis (Thysanoptera: Thripidae) in greenhouse ornamentals

The effectiveness of trap cropping as an integrated control strategy against western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was explored in potted chrysanthemum, Dendranthema grandiflora (Tzvelev), greenhouse crops. The efficacy of flowering chrysanthemum trap plants, either treated with the insecticide spinosad or untreated, to regulate F. occidentalis populations was tested at different spatial scales (small cage, large cage and commercial greenhouse) and for different time periods (1 or 4 weeks). It was demonstrated that flowering chrysanthemums as trap plants lower the number of adult F. occidentalis in a vegetative chrysanthemum crop and, as a result, reduce crop damage. In the 4 week large-cage trial and the commercial trial, significant differences between the control and the trap plant treatments started to appear in the third week of the experiment. Larvae were only significantly reduced by the presence of trap plants in the 1 week small-cage trials. There were no significant differences between treatments with spinosad-treated and untreated trap plants in the number of F. occidentalis on the crop. This suggests that there was minimal movement of adult F. occidentalis back and forth between the trap plants and the crop to feed and oviposit. It is concluded that the trap plant strategy is a useful tool for integrated pest management against F. occidentalis in greenhouses.     

应用实验种群生命表评价巴氏新小绥螨对西花蓟马的控制能力

以西花蓟马Frankliniella occidentalis(Pergande)(Thysanoptera,Thripidae)一龄若虫为猎物组建巴氏新小绥螨Neoseiulus barkeri(Hughes)(Acari:Phytoseiidae)实验种群生命表,获得净生殖力Ro=27.37,世代平均历期T=22.17天,内禀增长率rm=0.15,周限增长率λ=1.16,种群倍增所需时间t=4.64天等参数。将获得参数值与西花蓟马的相关参数值进行比较,巴氏新小绥螨瞬间增长率大于西花蓟马的瞬间增长率(0.14),雌成螨日取食7～12头西花蓟马一龄若虫,表明巴氏新小绥螨可以作为控制西花蓟马种群数量的有效天敌。     

Frankliniella occidentalis (Pergande) integrated pest management programs for fruiting vegetables in Florida

BACKGROUND: The spread of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), resulted in the worldwide destabilization of established integrated pest management programs for many crops. Efforts to control the pest and the thrips‐vectored tospoviruses with calendar applications of broad‐spectrum insecticides have been unsuccessful. The result has been a classic ‘3‐R’ situation: resistance to numerous insecticides; resurgence of the western flower thrips populations as a result of natural predators and native competitor thrips being eliminated; replacement by various other pests. This paper reports on integrated pest management programs for fruiting vegetables that are effective, economical, ecologically sound and sustainable. RESULTS: The components include the following: define pest status (economic thresholds); increase biotic resistance (natural enemies and competition); integrate preventive and therapeutic tactics (scouting, ultraviolet‐reflective technologies, biological control, compatible insecticides, companion plants and fertility); vertically integrate the programs with other pests; continually communicate latest science‐based management tactics with end‐users. CONCLUSION: These programs have been widely implemented in Florida and have significantly improved the management of western flower thrips and thrips‐transmitted viruses. Copyright © 2012 Society of Chemical Industry     

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.     

Effect of compost and casing treatments of insecticides against the sciarid Bradysia ocellaris (Diptera: Sciaridae) and on the total yield of cultivated mushrooms,Agaricus bisporus

BACKGROUND: Bradysia ocellaris (Comstock) is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. The feeding of sciarid fly larvae causes damage to the cultivation substrates, compost and casing. A comparative study of insecticidal treatments incorporated into compost and casing against B. ocellaris was conducted during 2003–2004. Treatments with an organophosphate, diazinon, a pyrazole, fipronil, and an insect growth regulator (IGR), triflumuron, were incorporated into casing. Another IGR, cyromazine, was incorporated into compost. Insecticidal incorporation into compost and casing has been associated with reductions in mushroom yield. Therefore, the effect of these insecticidal treatments on the overall yield was evaluated. RESULTS: A combined treatment, incorporation of cyromazine at 10 mg kg^?1 into compost and of triflumuron at 20 mg kg^?1 into casing, provided 100% control against B. ocellaris. There was no apparent reduction in yield as a result of incorporation of the tested chemicals into either compost or casing. CONCLUSION: The results obtained from this study suggest that incorporation of insecticides into both compost and casing is required to control a moderate to high pressure of insect pests. There were no significant yield reductions as a result of the incorporation of pesticides in the Australian mushroom‐growing system. Copyright © 2009 Society of Chemical Industry     

Compatibility of spinosad with predaceous mites (Acari) used to control Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

BACKGROUND: Spinosad is a biopesticide widely used for control of Frankliniella occidentalis (Pergande). It is reported to be non‐toxic to several predatory mite species used for the biological control of thrips. Predatory mites Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese) have been used for control of F. occidentalis. This study investigated the impact of direct and residual toxicity of spinosad on F. occidentalis and predatory mites. The repellency of spinosad residues to these predatory mites was also investigated. RESULTS: Direct contact to spinosad effectively reduced the number of F. occidentalis adults and larvae, causing > 96% mortality. Spinosad residues aged 2–96 h were also toxic to F. occidentalis. Direct exposure to spinosad resulted in > 90% mortality of all three mite species. Thresholds for the residual toxicity (contact) of spinosad (LT₂₅) were estimated as 4.2, 3.2 and 5.8 days for T. montdorensis, N. cucumeris and H. miles respectively. When mites were simultaneously exposed to spinosad residues and fed spinosad‐intoxicated thrips larvae, toxicity increased. Residual thresholds were re‐estimated as 5.4, 3.9 and 6.1 days for T. montdorensis, N. cucumeris and H. miles respectively. Residues aged 2–48 h repelled T. montdorensis and H. miles, and residues aged 2–24 h repelled N. cucumeris. CONCLUSION: Predatory mites can be safely released 6 days after spinosad is applied for the management of F. occidentalis. Copyright © 2011 Society of Chemical Industry     

Soil application of azadirachtin and 3-tigloyl-azadirachtol to control western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae): translocation and persistence in bean plants

To study the systemic effects of active neem ingredients, the substrate of bean plants was treated with a 170 g kg(-1) azadirachtin (NeemAzal-U; Trifolio-M GmbH, Lahnau, Germany, registration pending). This product was used at a dose rate of 10 mg AZA (azadirachtin a) and 1.2 mg 3-tigloyl-azadirachtol (azadirachtin b) per treated bean plant. Afterwards, the translocation and persistence of AZA and 3-tigloyl-azadirachtol and the effects on western flower thrips, Frankliniella occidentalis (Pergande), were studied. Residues of AZA and 3-tigloyl-azadirachtol from substrates with different contents of organic matter [pure culture substrate (CS), CS-sand mixture] and from various plant parts were quantified by high-performance liquid chromatography-mass spectrometry (HPLC-MS). The dissipation trends of AZA and 3-tigloyl-azadirachtol were similar within the same substrates. A slower decline of both active ingredients was measured with CS than with CS-sand mixture. Residue analysis of the bean plants showed that only small proportions of the initial amounts of AZA and 3-tigloyl-azadirachtol applied to the substrate were present in the plant (0.3-8.1%). Variable amounts of residues of the active components in relation to plant parts and time of analysis indicated a different translocation pattern for the two active ingredients. Higher residues of the active ingredients were found in roots and stems after neem application using CS, whereas higher residues were found in leaves after CS-sand mixture treatments. Mortality of F. occidentalis after NeemAzal-U soil applications reached up to 95% on CS-sand mixture, compared with 86% in CS.     

西花蓟马天敌种类及主要种类的控害潜能

西花蓟马[Frankliniella occidentalis(Pergande)]是国际上备受关注的检疫性有害生物,近年来该虫分布范围不断扩大,对农作物、园林园艺植物的危害日趋加重,发挥天敌对该虫的自然控制作用已引起人们广泛重视。本文根据国内外研究报道,总结和记述了西花蓟马的天敌种类及其主要种类对西花蓟马的控制作用。西花蓟马的天敌约有60种,其中天敌昆虫50种,昆虫病原线虫5种,虫生真菌5种。同时,对主要天敌种类小花蝽、昆虫病原线虫和虫生真菌对西花蓟马的捕食寄生及控制潜力进行了阐述。     

Synergism studies with binary mixtures of pyrethroid, carbamate and organophosphate insecticides on Frankliniella occidentalis (Pergande)

The major mechanism of resistance to most insecticides in Frankliniella occidentalis (Pergande) is metabolic, piperonyl butoxide (PBO) suppressible, mediated by cytochrome-P450 monooxygenases and conferring cross-resistance among insecticide classes. The efficacy of insecticide mixtures of acrinathrin, methiocarb, formetanate and chlorpyrifos was studied by topical exposure in strains of F. occidentalis selected for resistance to each insecticide. The method consisted in combining increasing concentrations of one insecticide with a constant low rate of the second one as synergist. Acrinathrin activity against F. occidentalis was enhanced by carbamate insecticides, methiocarb being a much better synergist than formetanate. Monooxygenase action on the carbamates would prevent degradation of the pyrethroid, hence providing a level of synergism by competitive substrate inhibition. However, the number of insecticides registered for control of F. occidentalis is very limited, and they are needed for antiresistance strategies such as mosaics and rotations. Therefore, a study was made of the synergist effect of other carbamates not used against thrips, such as carbofuran and carbosulfan, against a susceptible strain and a field strain. Neither carbamate showed synergism to acrinathrin in the susceptible strain, but both did in the field strain, carbosulfan being a better synergist than carbofuran. The data obtained indicate that low rates of carbamates could be used as synergists to restore some pyrethroid susceptibility in F. occidentalis.     

温度对西花蓟马、花蓟马存活和繁殖的影响

在室内研究了19、22、25、28和31℃条件下两种蓟马在辣椒上的存活率、成虫寿命、繁殖力及生命参数,以揭示温度对入侵害虫西花蓟马Frankliniella occidentalis和本地害虫花蓟马Frankliniellaintonsa的影响。结果显示,在19～31℃范围内两种蓟马雌、雄成虫寿命均随温度的升高而缩短,内禀增长率随温度的升高而增大,西花蓟马和花蓟马皆是在31℃时最高,分别为0.1347和0.1822。两种蓟马的种群趋势指数及净增殖率与温度之间呈曲线关系。在相同温度条件下,西花蓟马在各温度下的存活率高于花蓟马,但内禀增长率低于花蓟马。西花蓟马的繁殖力、种群趋势指数及净增值率在22℃时最高,花蓟马在25℃时最高。两种蓟马对温度的适应能力不同,22℃是西花蓟马的最适温度,而25℃更适合于花蓟马。     

Thrips (Thysanoptera: Thripidae) mitigation in seedling cotton using strip tillage and winter cover crops

BACKGROUND: Thrips are the most consistent insect pests of seedling cotton in the southeastern United States, where symptoms can range from leaf curling to stand loss. In a 2 year study, thrips adults and immatures were sampled at 14, 21 and 28 days after planting on cotton planted with a thiamethoxam seed treatment in concert with crimson clover, wheat or rye winter cover crops and conventional or strip tillage to investigate potential differences in thrips infestations. RESULTS: Densities of adult thrips, primarily Frankliniella fusca (Hinds), peaked on the first sampling date, whereas immature densities peaked on the second sampling date. Regardless of winter cover crop, plots that received strip tillage experienced significantly fewer thrips at each sampling interval. In addition, assessment of percentage ground cover 42 days after planting showed that there was more than twice as much ground cover in the strip‐tilled plots compared with conventionally tilled plots. Correlation analyses showed that increased ground cover was inversely related to thrips densities that occurred on all three sampling dates in 2008 and the final sampling date in 2009. CONCLUSIONS: Growers who utilize strip tillage and a winter cover crop can utilize seed treatments for mitigation of early‐season thrips infestation. Copyright © 2010 Society of Chemical Industry     

The proportion of viruliferous individuals in field populations of Frankliniella occidentalis: Implications for tomato spotted wilt virus epidemics in tomato

Tomato spotted wilt tospovirus (TSWV) infected plants and western flower thrips (Frankliniella occidentalis Perg., WFT) adult population densities were monitored during 1993 and 1994 in field tomatoes in Northeastern Spain. The proportion of viruliferous WFT adults in field populations was quantified. A significant association has been found between early population densities of WFT adult thrips and final TSWV incidence for early transplanted tomato crops. In contrast, for late transplanted tomato crops, whereas similar high final disease incidences of TSWV could be attained, very low WFT adult population densities were always detected. The significantly higher infectious potential of WFT populations collected during the early growth stages of late transplanted tomatoes could be relevant for the TSWV incidences attained in spite of the low thrips numbers detected.     

Effects of a juvenile hormone analog,pyriproxyfen, on Thrips tabaci (Thysanoptera: Thripidae)

Effects of a juvenile hormone analog, pyriproxyfen, on various developmental stadia of the onion thrips, Thrips tabaci Lindeman, were determined on cabbage leaves in the laboratory. Pyriproxyfen was applied at 0.064 or 0.128 g AI liter(-1) on leaves (residual contact-ingestion), thrips (direct contact) and leaf-thrips (residue contact-ingestion-direct contact). Pyriproxyfen did not have any significant lethal effects on thrips pupae in any treatment. Lethal effects on thrips larvae varied depending on application method and dosage. In the leaf and the leaf-thrips treatments, few larvae and pre-pupae molted to the next stage, and none developed to adults. In contrast, in the thrips-only treatment, pyriproxyfen did not show any significant lethal effects. The developmental times of larvae and pre-pupae were prolonged when larvae were treated with pyriproxyfen, and those of pre-pupae and pupae were shortened when pre-pupae and pupae were treated. The longevity and survival rates of thrips adults were generally shorter when they contacted and ingested pyriproxyfen-treated leaves than those in water control. Significantly fewer progeny (0.22-1.15 larvae per female) were produced by females that had fed on and been in contact with the pyriproxyfen-treated leaves than by those in the water control (11.94 larvae per female). However, the number of progeny produced by the thrips females increased significantly (3.32-7.28 larvae per female) when the females were transferred to untreated leaves after feeding on treated leaves for 5 days; the daily larval hatching pattern was similar to those in water control, indicating that female adults were able to produce viable eggs when untreated food was offered.     

西花蓟马分类鉴定方法的研究进展

西花蓟马Frankliniella occidentalis(Pergande)是一种危险性外来入侵害虫,虫体小,鉴定困难。本文总结了国内外西花蓟马分类鉴定方法的研究进展,包括形态学鉴别、分子生物学方法以及基于表皮碳氢化合物分析的生化分类方法,并讨论了各种分类方法的优势和弊端,最后对西花蓟马的分类研究前景进行了展望。     

Comparative analyses of the toxic effects of imidacloprid and spirotetramat on Frankliniella occidentalis (Pergande), the vector of tomato zonate spot virus: a laboratory assay

The tomato zonate spot virus (TZSV) is responsible for substantial yield losses in vegetables, tobacco and other cash crops in China in recent years. The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae), is the main vector of TZSV in Yunnan Province. Because controlling the population of insect vectors is the most efficient way to prevent epidemics of viral diseases, we conducted laboratory assays to assess the potential of using spirotetramat as an alternative to imidacloprid in controlling F. occidentalis. Our results demonstrated that spirotetramat was significantly more lethal than imidacloprid to F. occidentalis at different concentrations. The LC₃₀, LC₅₀ and LC₉₀ values of spirotetramat were all much lower than those of imidacloprid after the same time of treatment. Frankliniella occidentalis was more sensitive when treated with spirotetramat than imidacloprid at the concentrations of 500, 250, 125 and 62.5mg/L, and the median lethal concentrations (LC₅₀) were 285.53, 82.24 and 11.19mg/L at 12, 36 and 72 hours after treatment, respectively. Spirotetramat caused 100% mortality of F. occidentalis at 500 and 250 mg/L after 48 hours treatment, and at the lowest concentration 125 mg/L at 72 hours after treatment, respectively. Field experiments carried out elsewhere have confirmed our findings. Together they allow us to conclude that spirotetramat is a promising pesticide for the control F. occidentalis in China.