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.     

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 .     

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.     

Management of thrips (Thysanoptera: Thripidae) in Australian strawberry crops: within-plant distribution characteristics and action thresholds

Abstract  Management of thrips in a hydroponic strawberry crop near Sydney, New South Wales, was studied from 1999 to 2002. The main species present were western flower thrips, Frankliniella occidentalis (Pergande), plague thrips, Thrips imaginis Bagnall, and, occasionally, onion thrips, Thrips tabaci Lindeman. Their within- and between-plant distribution and the degree and type of damage caused are described, and used to recommend action thresholds. Flowers are identified as the primary monitoring site, and young green fruit as the key damage site. Action thresholds of approximately 45% of flowers with 5 or more adult western flower thrips, or 40% of flowers with 10 or more adult plague thrips are recommended. Alternative thresholds using all motile stages are given for flowers, and for young green and red berries. A higher tolerance is recommended during cool, wet periods.     

Host plant, temperature, and photoperiod effects on ovipositional preference of Frankliniella occidentalis and Frankliniella fusca (Thysanoptera: Thripidae)

Host plant effects of tomato, Lycopersicon esculentum Mill., and chickweed, Stellaria media (L.) Vill., foliage infected and uninfected with Tomato spotted wilt virus (family Bunyaviridae, genus Tospovirus, TSWV) on the ovipositional preferences of western flower thrips, Frankliniella occidentalis (Pergande), and tobacco thrips, Frankliniella fusca (Hinds), were investigated for whole plants in the greenhouse. In addition, the preference for leaf disks from the same host plants was investigated under a range of temperatures, 15-30 degrees C at a photoperiod of 12:12 (L:D) h, and at three photoperiods, 6:18, 12:12, and 18:6, at 20 degrees C in no-choice and choice studies conducted in growth chambers. In a choice test, F. fusca oviposited significantly more eggs per whole plant foliage over a 7-d period than F. occidentalis by an average ratio of 3:1 over both tomato and chickweed. The optimum temperature for oviposition of F. occidentalis and F. fusca was 24.5 and 24.9 degrees C, respectively. Both species laid significantly more eggs under the longest daylight hours tested, 18:6, in the choice study. Temperature and photoperiod did not significantly interact in terms of thrips ovipositional preference. Ovipositional preference for chickweed or tomato foliage was different for each thrips species in the choice and no-choice tests. However, both thrips species laid significantly more eggs per square centimeter of leaf area in chickweed than in tomato in the whole plant choice test.     

Manipulating fertilization: a management tactic against Frankliniella occidentalis on potted chrysanthemum

Fertilization during production of greenhouse chrysanthemum, Dendranthema grandiflora (Tzvelev), will influence Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) populations as well as plant productivity and postproduction longevity. It is essential to include fertilization effects in the development of crop management practices that reduce thrips populations and maintain plant marketability. In this study, we lowered fertilization to reduce thrips population abundance while maintaining plant productivity. We tested fertilization levels below and above the recommended level (375 p.p.m. N) for commercial production. We reduced mean rate of change in F. occidentalis abundance from 0.05 to 0.03 (day⁻¹) and mean number of thrips per plant by 44% by fertilizing with either 188 p.p.m. N (50% of the recommended level) or 568 p.p.m. N (150%) and higher. Fertilization influenced not only the rate of change in thrips abundance but also the production time (from transplanting to flower opening). Lowering fertilization to 50% of the recommended level lengthened mean production time from 84 to 88 days. Plant height, flower size, and flower number were not adversely affected when fertilization was reduced to 50% of the recommended level. Mean postproduction longevity was shortened from 26 to 24 days when plants were fertilized with 50% of the recommended level. Two important advantages of lowering fertilization to 50% of the recommended level were (1) a 44% reduction in mean F. occidentalis abundance and (2) a significant reduction in fertilizer input for the production system. Manipulation of fertilization can be a useful management tactic against F. occidentalis .     

Variation in preference and performance of Frankliniella occidentalis (Thysanoptera: Thripidae) on three strawberry cultivars

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of strawberry, causing substantial yield loss through direct feeding on the flowers and fruit. Insecticides are the main method used for its control; however, F. occidentalis has developed resistance to insecticides from all major chemical classes. Chemical control is not a long-term strategy and integrated pest management is required. This study determined whether F. occidentalis damage could be reduced by host plant resistance or tolerance in three commercial strawberry cultivars (Fragaria X ananassa [Rosaceae]: 'Albion', 'Camarosa', and 'Camino Real'). Determination of resistance or tolerance to F. occidentalis was based on olfactory response, feeding damage, ovipositional preference, and host suitability for reproduction on leaves. F. occidentalis adults preferred to feed on Camarosa; however, if leaves had been fed on previously by conspecifics, there was no difference in feeding preference. Camarosa was the most preferred cultivar for oviposition, and more eggs were laid by F. occidentalis on Camarosa than either Albion or Camino Real. More larvae hatched and adults were reared from Camarosa than either Albion or Camino Real. The percentage of unhatched eggs, larvae, and pupae that died was highest on Camino Real. Survival rate was highest on Camarosa. Egg incubation, prepupation, pupation, and total developmental periods were shortest on Camarosa, but the larval period was longest on Camarosa. Camarosa was the most favorable cultivar for F. occidentalis population growth on leaves.     

Tactics for management of thrips (Thysanoptera: Thripidae) and tomato spotted wilt virus in tomato

Four studies were conducted in Georgia during spring 1999, 2000, 2001, and 2002 to evaluate various management tactics for reducing thrips and thrips-vectored tomato spotted wilt virus (TSWV) in tomato and their interactions relative to fruit yield. Populations of thrips vectors of TSWV, Frankliniella occidentalis (Pergande) and Frankliniella fusca (Hinds), were determined using flower and sticky trap samples. The management practices evaluated were host plant resistance, insecticide treatments, and silver or metallic reflective mulch. Averaged over all tests, the TSWV-resistant tomato 'BHN444' on silver mulch treatment had the largest effect in terms of reducing thrips and spotted wilt and increasing marketable yield. Of the insecticide treatments tested, the imidacloprid soil treatment followed by early applications of a thrips-effective foliar insecticide treatment provided significant increase in yield over other treatments. Tomato yield was negatively correlated with the number of F. fusca and percentage of TSWV incidence. F. occidentalis per blossom was positively correlated with percentage of TSWV incidence, but not with yield. No significant interactions were observed between cultivar reflective mulch main plot treatments and insecticide subplot treatments; thus, treatment seemed to be additive in reducing the economic impact of thrips-vectored TSWV. Control tactics that manage thrips early in the growing season significantly increased tomato yield in years when the incidence of TSWV was high (>17%).     

Predatory effect of Orius niger (Wolff) (Hem., Anthocoridae) on Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman (Thysan., Thripidae)

The predatory effect of adult female Orius niger (Wolff) (Hem., Anthocoridae) on the larvae I–II and adults of two injurious thrips , Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman (Thysan., Thripidae), was examined in June 1997, in controlled environment chambers (temperature 22 ± 0.2°C, 65 ± 3% RH, a 16 h light : 8 h dark photoperiod and light intensity 9000 Lux). This study took place on sweet pepper leaves ( Capsicum annuum L.) in transparent small plastic cages at proportions of 1/5, 1/10, 1/20 and 1/30 predator/number of thrips for larvae I–II and adults separately for each thrips species. O. niger was proved an effective predator for the immature stages (larvae I–II) and for the adults of the two thrips species. We concluded that O. niger could be used with success for the biological control of thrips in greenhouses crops.     

Economic injury levels for western flower thrips (Thysanoptera: Thripidae) on greenhouse cucumber

Low, medium and high densities of western flower thrips, Frankliniella occidentalis (Pergande), were established in three greenhouses at the Greenhouse and Processing Crops Research Centre, Ontario, Canada, in 1996 and 1998 to develop economic injury levels for thrips on greenhouse cucumber. Thrips densities were monitored weekly using yellow sticky traps and flower counts. Fruit was harvested twice a week, graded for size, weighed, and rated for thrips damage using three damage categories. Significant yield reduction was detected 4 wk after severe fruit damage was observed in the high and medium thrips density treatments in 1996 and 7 wk in 1998. Percentage of severe damaged fruit (P(F3)) has significant linear relationships with the adult thrips density (x) that was sampled by sticky traps 1 wk before harvest (P(F3) = -0.2533 + 0.0828x) and that was sampled by flower counts 2 wk before harvest (P(F3) = -0.2025 + 0.5490x). Based on the regression equations, economic injury levels, expressed as adult thrips per sticky trap per day or adult thrips per flower, were calculated for various combinations of control costs, yield potential and fruit prices. The economic injury levels for F. occidentalis ranged from 20 to 50 adults per sticky trap per day or 3 to 7.5 per flower as determined under average greenhouse production conditions in Ontario, Canada.     

Population dynamics of Frankliniella spp. and tomato spotted wilt incidence as influenced by cultural management tactics in tomato

We investigated the effects of ultraviolet (UV)-reflective mulch and two rates of nitrogen fertilization on populations of Frankliniella spp. thrips and on the incidence of tomato spotted wilt in field-grown tomato in northern Florida. The higher of the two soil nitrogen fertilizer treatments significantly increased populations of Frankliniella occidentalis (Pergande), whereas mulch reflectance significantly decreased populations of F. occidentalis. Populations of Frankliniella tritici (Fitch) were decreased only by UV-reflective mulch. Decreased thrips populations in UV-reflective mulch plots were probably due to disruptions in host-finding behavior. Increased thrips populations in tomatoes treated with the higher nitrogen fertilization rate were probably due in part to increased nutrients available in flowers. Incidence of tomato spotted wilt was significantly decreased in tomatoes grown on UV-reflective mulch, whereas disease incidence was significantly greater in increased nitrogen-fertilized plots. This research reveals that cultural practices resulted in up to 45% reduction in the numbers of vector and nonvector species of flower thrips and up to 50% reduction in tomato spotted wilt.     

Flower visitation and oviposition behavior of Frankliniella occidentalis (Tysan., Thripidae) on cucumber plants

Oviposition behaviour of western flower thrips, Frankliniella occidentalis (Pergande) on greenhouse cucumber, Cucumis satifus (L.) was investigated. Most eggs were laid in the leaves, along veins and under leaf hairs, with only a few on plant stems and flowers. Oviposition rate was higher during the day than during the night. During the day, more adult thrips were found in the flowers than during the night. The number of adult thrips per flower increased rapidly after sunrise with the highest densities occurring around noon and thereafter the number of thrips in flowers decreased during the afternoon. No differences were found in the number of larvae (first and second instars) in flowers during the same period. The number of adult thrips on male and female cucumber flowers was not different, indicating that pollen is not the only attraction in flowers for thrips.     

In vivo rearing of Thripinema nicklewoodi (Tylenchida: Allantonematidae) and prospects as a biological control agent of Frankliniella occidentalis (Thysanoptera: Thripidae)

Methods are described for the in vivo production of the nematode Thripinema nicklewoodi (Siddiqi), an obligate parasite and potential biological control agent of western flower thrips Frankliniella occidentalis (Pergande). Nematode infection is not lethal but causes sterilization of adult female hosts. Both fertilization and horizontal transmission of T. nicklewoodi is achieved in 1.5-ml microcentrifuge tubes (infection arenas), in the presence of 100% humidity, a temporary food source and preferably a damp substrate. Following exposure to infection arenas, F. occidentalis are reared on excised bean leaves Phaseolus vulgaris (L.) in polypropylene containers for 2 wk at 25 degrees C to allow the reproduction and development of a single generation of nematodes within infected hosts's abdominal cavity. To identify infected hosts after this incubation period, thrips are isolated in microcentrifuge tubes and monitored for free-living nematodes being released along with frass. Infected thrips are reintroduced back into infection arenas to inoculate further thrips to maintain the culture. We documented the output of the rearing procedure using a standard method and following simple manipulation of several individual parameters of the infection technique. The standard method was the most efficient, and resulted in an increased (output/input) ratio of infected thrips of approximately 2; i.e., the number of infected thrips approximately doubles each generation. Monitoring infected thrips revealed that nematodes were first released between 12-14 d postinfection and for an average of 7.9 d at 25 degrees C; highlighting the potential to reuse infective thrips between infection arenas. The possibility of using T. nicklewoodi as an inoculative agent against F. occidentalis infesting floricultural crops is discussed.     

Daily flight activity of the western flower thrips (Thysan., Thripidae) in nectarine orchards in British Columbia, Canada

Abstract:   Hourly flight patterns of western flower thrips, Frankliniella occidentalis (Pergande) (Thysan., Thripidae) were assessed over a 24 h period in two nectarine orchards located in the Similkameen Valley, British Columbia, on 13 separate occasions between March and October 1994. The numbers of western flower thrips (male or female, dark or pale morphs) trapped per hour at between four to eight heights (0.25–2.00 m) were compared with temperature, wind speed, time of year and location of trap placement. Traps were placed within orchards, at the border of orchards and adjacent wild land, and within wildlands. Temperature and wind speed thresholds are defined, although the effect of wind speed varied with height of flight. Height of flight was affected by both the height of prevalent vegetation and temperature, with mean height of flight increasing linearly with temperature. Numbers of thrips in flight decreased with height of sticky trap from the ground. The pale morph was generally more common than the dark morph of western flower thrips. Males were not present until after emergence of the first generation in May, and were found at an approximate ratio of 4 : 1 (F : M) for the rest of the year. There were no differences between sexes or morphs of western flower thrips for location, height or daily patterns of flight.     

Systemic effects of neem on western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae)

The systemic effects of neem on the western flower thrips, Frankliniella occidentalis (Pergande), were investigated in laboratory trials using green bean, Phaseolus vulgaris L., in arena and microcosm experiments. In arena experiments, systemic effects of neem against western flower thrips larvae on primary bean leaves were observed with maximum corrected mortality of 50.6%. In microcosm experiments using bean seedlings, higher efficacy in the control of western flower thrips were observed with soil applications of neem on a substrate mixture (i.e., Fruhstorfer Erde, Type P, and sand) in a 1:1 ratio (93% corrected mortality) compared with application on the commercial substrate only (76% corrected mortality). However, longer persistence of neem was observed with soil application on the commercial substrate, which showed effects against thrips for up to 6 d after application. In addition to systemic effects observed on all foliage-feeding stages of western flower thrips, mortality on contact and repellent effects were observed on soil-inhabiting stages after soil applications of neem. Finally, bean seedlings grown from seeds pregerminated for 3 d in neem emulsion were also toxic to western flower thrips.     

重金属镉在番茄及其害虫西花蓟马中的积累与传递

重金属镉(Cd)是农田土壤中的重要污染源,可在植物和植食性昆虫中积累与传递。本文采用水培法,研究了不同浓度的Cd在番茄Solanum lycopersicum不同组织和在其重要害虫西花蓟马Frankliniella occidentalis体内的积累量。结果表明,随着水培营养液中Cd浓度的增加,番茄植株的根、茎和叶中Cd含量呈增长趋势。根中Cd的积累量远高于茎和叶,当水培溶液中Cd含量为20 mg/L时,根、茎和叶中的积累量分别达19 333.67±233.38、122.67±6.84和147.33±2.96 mg/Kg(干重)。随着Cd浓度的增加,番茄根、茎和叶的鲜重和干重均显著下降。西花蓟马取食Cd处理的番茄叶片后,体内Cd显著积累,最高达1.95±0.36 mg/Kg。同时,Cd积累量的提高进一步影响了以番茄叶片为食的西花蓟马的适合度,降低了其存活率。除对照外,番茄茎-叶的转移系数和叶片对Cd的富集系数均大于1,叶片表现出较强的富集能力。而在所有的试验浓度处理中,西花蓟马对Cd的富集系数和转移系数均小于1,表明Cd未在其体内产生生物放大作用。研究结果明确了Cd在番茄各组织及其害虫中的积累和传递水平,为揭示重金属在农业生态系统食物链中的富集效应提供了基础数据。     

Lack of fitness costs of insecticide resistance in the western flower thrips (Thysanoptera: Thripidae)

The fitness costs of spinosad and acrinathrin resistance was investigated in the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Fitness studies were conducted on susceptible and resistant strains of F. occidentalis. Resistant females were significantly more fecund (number of eggs per female) than susceptible females. The hatching rate (fertility) for both susceptible and acrinathrin-resistant strains was significantly lower than in the spinosad-resistant strain. Mean developmental time from egg to adult did not differ between thrips populations. Similarly, female longevity did not differ between populations. These data suggest that lack of fitness costs related to insecticide resistance may accelerate the development of insecticide resistance in populations of F. occidentalis from southeastern Spain.     

接种番茄斑萎病毒番茄植株对西花蓟马生物学特性的影响

西花蓟马Frankliniella occidentalis(Pergande)是我国的一种重要入侵害虫。本文研究了西花蓟马在番茄3种处理(健康CK、机械接种番茄斑萎病毒MI、机械损伤MD)叶片上的生长发育、存活及种群增长。结果表明:健康、机械接种番茄斑萎病毒、机械损伤叶片上的发育历期依次为12.68、12.99和11.79d。雌雄成虫寿命和雌虫繁殖能力在各处理叶片上差异不显著(P>0.05)。健康、机械接种番茄斑萎病毒、机械损伤叶片上的内禀增长率依次为0.1362、0.1526和0.1292d-1。本研究表明,接种番茄斑萎病毒的番茄叶片未缩短西花蓟马发育历期,也不能延长寿命及提高产卵量,不能明显加速种群数量增长。这意味着番茄斑萎病毒对西花蓟马在番茄叶片上的生物学特性未能产生明显的有利作用。     

西花蓟马的SCAR分子检测技术

西花蓟马Frankliniella occidentalis （Pergande）是一种世界性入侵害虫,寄主范围广,危害严重,2003年首次在我国发生危害,并有进一步扩散蔓延的趋势。针对蓟马类害虫虫体微小、形态相似,难以准确快速区分的问题,采用特征序列扩增区域（SCAR）标记技术,以西花蓟马及与之同域发生的其他种类蓟马为对象,筛选出1对西花蓟马特异性引物（FOMF/FOMR）,其扩增片段大小为320 bp。种特异性检测结果显示,该对引物只对西花蓟马的基因组DNA具有扩增能力,对同域发生的花蓟马F. intonsa （Trybom）、禾花蓟马F. tenuicornis （Uzel）、烟蓟马Thrips tabaci L. 等41种蓟马不具有扩增效果。该对引物不仅对不同虫态的西花蓟马具有扩增能力,而且在西花蓟马发生地的寄主植物组织内亦检测到了其卵的存在。同时,该检测技术灵敏度高,对成虫的最低检出阈值为1/160头。本检测技术在口岸检疫以及花卉、蔬菜和种苗调运中的害虫检测和监测中具有重要意义。     

Integrated management tactics for Frankliniella thrips (Thysanoptera: Thripidae) in field-grown pepper

In a 2-yr study, the impacts of different plastic soil mulches, insecticides, and predator releases on Frankliniella thrips and their natural enemies were investigated in field-grown peppers. Ultraviolet light (UV)-reflective mulch significantly reduced early season abundance of adult thrips compared with standard black plastic mulch. This difference diminished as the growing seasons progressed. Late season abundance of thrips larvae was higher in UV reflective mulch compared with black mulch plots. The abundance of the predator Orius insidiosus (Say) was significantly lower in UV-reflective mulch compared with black mulch treatments. Infection of plants with tomato spotted wilt virus, a pathogen vectored by Frankliniella occidentalis (Pergande), was <6%. In the year with the higher disease incidence (2000), UV-reflective mulch plots had significantly less disease (1.9%) compared with black mulch plots (4.4%). Yield was significantly higher in UV-reflective mulch (24,529 kg/ha) compared with black mulch (15,315 kg/ha) during this year. Effects of insecticides varied with species of thrips. Spinosad reduced abundance of F. occidentalis, but not Frankliniella tritici. In contrast, esfenvalerate and acephate reduced numbers of F. tritici and Frankliniella bispinosa, but resulted in higher populations of F. occidentalis. Spinosad was the least disruptive insecticide to populations of O. insidiosus. Releases of O. insidiosus and Geocoris punctipes (Say) reduced populations of thrips immediately after releases; naturally occurring predators probably provided late season control of thrips. Our results suggest that UV-reflective mulch, combined with early season applications of spinosad, can effectively reduce abundance of thrips in field-grown pepper.