Analysis of the thrips fauna (Thysanoptera) on flowers of herbs

Studies of Thysanoptera were realized at the Agricultural Experimental Station in Mydlniki near Cracow over the years 2003-2005. This research work covers the observations of the species composition of thrips and the periods of the occurrence of the particulars species of thrips and their numerousness. The thrips were collected from flowers of Valeriana officinalis L., Hypericum perforatum L. and Levisticum officinale Koch. Following thrips species dominated samples collected directly from plants: Frankliniella intonsa (Trybom), Thrips fuscipennis Haliday, Thrips tabaci Lindeman and Thrips major Uzel. The greatest number of thrips was noticed during flowering period on Valeriana officinalis L., and Hypericum perforatum L.     

Within-plant distribution of onion thrips (Thysanoptera: Thripidae) in onions

Two aspects of the within-plant distribution of Thrips tabaci Lindeman (Thysanoptera: Thripidae) on onion, Allium cepa L., plants were investigated: 1) diurnal variations in the distribution of adults and larvae between basal and upper sections of onion leaves, and 2) between-leaf and within-leaf distribution of the eggs. The diurnal investigations showed that higher proportions of larvae than of adults congregated at the basal sections of plants, particularly when plants were young and thrips density was low. As plants matured and thrips density increased, the larvae became more dispersed. Regardless of plant size, there were always more adults in the upper than basal plant sections. There were no clear time-windows during the 24-h diurnal cycle when more thrips were in the upper plant parts. T. tabaci eggs were laid everywhere in the plant. Leaves of intermediate ages had more eggs than older or younger leaves. Within leaves, the white leaf sheath received the least eggs and leaf tips received slightly more eggs than leaf sheaths. The highest egg density was found between the green leaf base and the leaf tips. Regardless of plant size, more than half of all eggs were laid above the basal sections. The percentage increased to >95% in mature plants. Except when plants were small the outer leaves were preferred over inner leaves and upper leaf sections preferred over lower leaf sections as egg-laying sites by adults. Implications of the results in the management of T. tabaci are discussed.     

Onion thrips (Thysanoptera: Thripidae): a global pest of increasing concern in onion

During the past two decades, onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), has become a global pest of increasing concern in commercial onion (Allium cepa L.), because of its development of resistance to insecticides, ability to transmit plant pathogens, and frequency of producing more generations at high temperatures. T. tabaci feeds directly on leaves, causing blotches and premature senescence as well as distorted and undersized bulbs. T. tabaci can cause yield loss > 50% but can be even more problematic when it transmits Iris yellow spot virus (family Bunyaviridae, genus Tospovirus, IYSV). IYSV was identified in 1981 in Brazil and has spread to many important onion-producing regions of the world, including several U.S. states. IYSV symptoms include straw-colored, dry, tan, spindle- or diamond-shaped lesions on the leaves and scapes of onion plants and can cause yield loss up to 100%. Here, we review the biology and ecology of T. tabaci and discuss current management strategies based on chemical, biological, and cultural control as well as host resistance. Future directions for research in integrated pest management are examined and discussed.     

Characterization of resistance, evaluation of the attractiveness of plant odors, and effect of leaf color on different onion cultivars to onion thrips (Thysanoptera: Thripidae)

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a worldwide pest of onion, Allium cepa L. In field studies on onion resistance conducted in 2007 and 2008 using 49 cultivars, 11 showed low leaf damage by T. tabaci. In laboratory studies, the 11 cultivars, along with two susceptible checks and four additional cultivars, were evaluated to characterize resistance to T. tabaci and to determine if color and/or light reflectance were associated with resistance to T tabaci. No-choice tests were performed with adults and the numbers of eggs and larvae were counted on each cultivar after three and 10 d, respectively. In choice tests in which all cultivars were planted together in a circle in a single pot, 100 adults were released and the number of adults on each plant was evaluated 24 h later. The behavioral response of walking T. tabaci adults to plant odors was studied in a glass Y-tube olfactometer. The reflectance spectrum of leaves was measured using a UV-VIS spectrophotometer. Results indicate that resistant cultivars showed an intermediate-high antibiotic effect to T. tabaci and all of them showed a very strong antixenotic effect. There were no significant preferences in the response of walking T. tabaci adults to plant odors. The two susceptible cultivars had the highest values of leaf reflectance for the first (275-375 nm) and second (310-410 nm) theoretical photopigment-system of T. tabaci, and these values were significantly different from most resistant cultivars. These results suggest a strong response of T. tabaci to onion cultivars with higher reflectance in the ultraviolet range (270-400 nm). Overall, these results appear promising in helping to identify categories of resistance to T. tabaci in onions that can be used in breeding programs.     

The discovery of a new species of Ceranisus from southwestern Turkey

An explorative trip was made to southwesternTurkey in April 1995 in search of pear thrips,Taeniothrips inconsequens (Uzel)(Thysanoptera: Thripidae), and its naturalenemies. Forty-three females and 13 males of apreviously undescribed species of the genusCeranisus Walker (Hymenoptera:Eulophidae) were found, mainly in floweringArbutus andrachne L. Although theparasitoid was found in association withseveral thrips species, but especially T.inconsequens adults and larvae, its host orhosts were not determined. The parasitoid isdescribed and given the name Ceranisusantalyacus S. Triapitsyn.     

Impact of straw mulch on populations of onion thrips (Thysanoptera: Thripidae) in onion

Development of insecticide resistance in onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), populations in onion (Allium spp.) fields and the incidence of the T. tabaci transmitted Iris yellow spot virus have stimulated interest in evaluating alternative management tactics. Effects of straw mulch applied in commercial onion fields in muck areas of western New York were assessed in 2006 and 2007 as a possible onion thrips management strategy. In trials in which no insecticides were applied for thrips control, straw mulch-treated plots supported significantly lower T. tabaci populations compared with control plots. In both years, the action thresholds of one or three larvae per leaf were reached in straw mulch treatments between 7 and 14 d later than in the control. Ground predatory fauna, as evaluated by pitfall trapping, was not increased by straw mulch in 2006; however, populations of the common predatory thrips Aeolothrips fasciatus (L.) (Thysanoptera: Aeolothripidae) were significantly lower in straw mulch plots in both years. Interference of straw mulch in the pupation and emergence of T. tabaci was investigated in the lab and their emergence was reduced by 54% compared with bare soil. In the field the overall yield of onions was not affected by the straw mulch treatment; however, the presence of jumbo grade onions (>77 mm) was increased in 2006, but not in 2007. These results indicate that populations of T. tabaci adults and larvae can be significantly reduced by the use of straw mulch without compromising overall onion yield. The use of this cultural practice in an onion integrated pest management program seems promising.     

Population dynamics of banded thrips (Aeolothrips intermedius Bagnall, Thysanoptera, Aeolothripidae) and its potential prey Thysanoptera species on white clover

In 2002, the occurrence of banded thrips (Aeolothrips intermedius Bagnall) and some other Thysanoptera species on white clover (Trifolium repens L.) was monitored at two locations in the continental part of Slovenia. White clover presents in many countries important intercrop in integrated vegetable production. Light blue sticky boards were placed on grasslands (one parcel on each location) with high percentage of white clover. Sticky boards were changed in about 10-days intervals from the end of April till the beginning of October. Number of caught individuals on the boards was counted. They were classified in three different groups: 1. Aeolothrips intermedius, 2. representatives of Haplothrips, Odontothrips and Frankliniella genera, 3. representatives of Thrips genus. We stated that, compared with the other Thysanoptera species in the open, predatory thrips occurs in lower number. Predatory species Aeolothrips intermedius was the most numerous during the flowering of white clover. It was established that other Thysanoptera species (the most of them are facultative phytophagous species) were more numerous also in the periods of less favourable weather conditions and during the non-flowering growing stages of white clover. Based on the results of present research we concluded that A. intermedius has a potential to control onion thrips (Thrips tabaci Lindeman), especially in July and August, when in the open both species occur in high numbers.     

Overwintering locations and hosts for onion thrips (Thysanoptera: Thripidae) in the onion cropping ecosystem in New York

Identifying locations where onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), overwinter and subsequently disperse is important for designing control strategies. In upstate New York from 2003 through 2006, potential overwintering sites in the commercial onion, Allium cepa L., cropping system were investigated early in the spring before onion seedling emergence and again late in the season after onions were harvested. Onion thrips adults were sampled directly from the soil and indirectly from the soil by using emergence cages. Sampling locations included onion field interiors and edges and areas outside of these fields, including woods. Host material sampled included onion culls; volunteer onions, which sprout from cull onions left behind after harvest; and weeds. Onion thrips adults were found in all sections of onion fields and in locations outside of onion fields, with the fewest emerging from woods. Emergence began in early May and extended into June. Peak emergence occurred during the last half of May, at which time 50-75% of the population had emerged. Adults colonized volunteer onions as early as late March and as late as mid-November. No adults were found overwintering in onion cull piles. Adults also colonized several weed species, especially pigweed, Amaranthus hybridis L., and lambsquarters, Chenopodium album L., late in the fall. Our results indicate that onion thrips adults overwinter in the soil within and near onion fields and that they probably colonize volunteer onion plants before subsequent generations infest the onion crop in the spring. Volunteer onions and weeds also provide onion thrips with a host after onions are harvested. Consequently, onion thrips management strategies should include tactics that reduce volunteer onion and weed abundance.     

Evaluation of visual and olfactory cues for sampling three thrips species (Thysanoptera: Thripidae) in deciduous forests of the northern United States

The introduced basswood thrips, Thrips calcaratus Uzel pear thrips, Taeniothrips inconsequens (Uzel), and native basswood thrips, Neohydatothrips tiliae (Hood), form a thrips complex that attacks buds and foliage of basswood, Tilia americana L., trees in the northern United States. We assessed the potential for exploiting visual and olfactory cues to monitor these forest thrips. We tested blue, green, red, white, and yellow for thrips' response to visual stimuli, and anisaldehyde, ethyl nicotinate, and polar and nonpolar extracts of basswood buds or leaves for thrips' response to olfactory stimuli over a 2-yr period. Generally, yellow traps tended to elicit the greatest visual response from all three species. None of the species showed significant attraction to the test volatiles compared with controls. The introduced basswood thrips, which is closely associated with expanding buds, was the most abundant species, and occurred earlier in the spring than the two flower- or foliage-associated species. The implications of these behaviors are discussed with respect to a forest pest monitoring program.     

Advances in control of onion thrips (Thysanoptera: Thripidae) in cabbage

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), feeding injury results in discoloration and a rough texture on cabbage, Brassica oleracea capitata (L.), leaves, and damage may occur deep inside the head. It has become a key pest of cabbage in the United States and many other countries. Previous studies have indicated poor control using insecticides. The present study identified imidacloprid drenches and sprays of acetamiprid, dimethoate, spinosad, and imidacloprid as insecticides that performed better than the industry standard, lambda-cyhalothrin. However, additional tests with foliar sprays of dimethoate and acetamiprid indicated there was not an ideal crop stage (precupping, cupping, or postcupping) at which either insecticide could be applied for reliable control of T. tabaci, possibly because of multiple flights of thrips into the crop or the asynchrony of flights and susceptible crop stages. In tests in a commercial field, a soil drench of imidacloprid 4 wk after transplanting reduced the number of damaged leaves in the head by 32%, whereas five sprays of acetamiprid reduced damage by 51%. Combining both insecticide regimes reduced damage by 85%, but resulted in a very costly management program. Cabbage varieties varied considerably in susceptibility with some having negligible thrips injury, regardless of being treated with an insecticide. Planting date affected susceptibility of cabbage to some degree, but not as much as other tactics. Overall, these studies indicate that increased emphasis should be placed on breeding cabbages to be resistant to T. tabaci as the foundation for its management.     

Effects of undersown clover on host-plant selection by Thrips tabaci adults in leek

The suppressive effects of undersown clover on Thrips tabaci Lindeman infestation in leek is known but not the stages in thrips population dynamics that are affected by intercropping and the mechanisms involved. Colonization or settling of adult onion thrips (T. tabaci) in monocropped leek (Allium porrum L.) and in leek intercropped with strawberry clover (Trifolium fragiferum L.) was studied in two potted plant experiments. Potted leek plants with and without undersown clover were placed for a short period (2 and 5 days) in monocropped or intercropped field plots when high thrips infestation was expected. Thrips adults were counted on all leaves and in the shaft during this observation period. Thrips populations were monitored weekly in the field plots throughout the entire growing season.In both potted plant experiments, there were consistently fewer thrips adults on intercropped leek plants than on monocropped plants. The plant growth parameters – number of leaves and stem diameter – were similar in all treatments and thus did not explain differences in thrips adults. Natural enemies were absent on both leek and clover, and thus cannot explain the differences in adult thrips numbers. Furthermore, no adults of T. tabaci were found on the clover in the potted plant experiment and only very few in the field experiment. Thus it was concluded that strawberry clover was not an effective trap crop for thrips.In the second potted plant experiment, clover was removed just before the leek plants were introduced to the field, thus eliminating direct physical, visual and olfactory interference by clover. After the undersown clover was removed, the leek plants harboured only one-third of the number of thrips adults, as compared to the monocropped plants. This study supports the notion that there are subtle links between intercropping and plant quality, and indicates that host-plant quality is an underlying cause of the reduction in adult thrips numbers in leek/clover intercropping.     

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.     

西花蓟马与烟蓟马生物学特性的比较研究

本试验研究并比较了外来入侵物种西花蓟马Frankliniella occidentalis(Pergande)与本地物种烟蓟马Thrips tabaci Lindeman的生物学特性,包括种群增长速度、发育历期、成虫寿命、孤雌生殖方式下的产卵量以及产卵规律等几个方面。结果显示,当以相同的数量在紫甘蓝上饲养时,只经过3代,烟蓟马的种群数量就可以达到西花蓟马的3倍,随后对2种蓟马种群的性别比进行了鉴定后发现,西花蓟马种群的雌雄比为2.8∶1,而烟蓟马种群中的所有个体均为雌性。除了2龄若虫期和预蛹期之外,烟蓟马在紫甘蓝上的发育历期明显长于西花蓟马,而其雌虫的平均寿命显著短于西花蓟马雌虫,分别是24.94d和43.35d。进行孤雌生殖时,西花蓟马的终生产卵量明显多于烟蓟马,但是在日均产卵量方面,这一情况却相反。     

Responses of Thrips tabaci to odours of herbivore‐induced cotton seedlings

Herbivore‐induced changes in plants have been widely viewed as defensive responses against further insect attack. However, changes in plants as a consequence of herbivore feeding can elicit various responses in herbivores; these are variable, context dependent, and often unpredictable. In this laboratory study, the responses of Thrips tabaci Lindeman (Thysanoptera: Thripidae) to volatiles emitted by intact and herbivore‐damaged or mechanically damaged cotton seedlings [Gossypium hirsutum L. (Malvaceae)] were investigated in dual‐choice olfactometer assays. Thrips tabaci showed increased attraction to seedlings subject to foliar mechanical damage and those with foliar damage inflicted by conspecifics or Tetranychus urticae Koch (Acari: Tetranychidae), upon which it preys. However, T. tabaci did not discriminate between intact seedlings and those with foliar damage inflicted by Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), two other species of thrips, Frankliniella schultzei Trybom and Frankliniella occidentalis Pergrande (Thysanoptera: Thripidae), or those with root damage inflicted by Tenebrio molitor L. (Coleoptera: Tenebrionidae). Attraction of T. tabaci was also affected by herbivore density on damaged plants. That is, seedlings damaged by higher densities of T. urticae or T. tabaci were more attractive than seedlings damaged by lower densities of the corresponding arthropod. Although attracted to plants damaged by conspecifics or T. urticae, T. tabaci showed greater attraction to seedlings damaged by T. urticae than to seedlings damaged by conspecifics. Results are discussed in the context of the responses of F. schultzei and F. occidentalis to herbivore‐induced cotton seedlings, highlighting the complexity, variability, and unpredictability of the responses of even closely related species of insects to plants under herbivore attack.     

Species of the genus Thrips from India (Thysanoptera)

Abstract. The species of Thrips Linnaeus from the Indian region are revised, and a key is provided to the thirty-three valid species, including eight new species and one new subspecies, Eight species customarily included in Taenio-thrips Amyot & Serville are here included in Thrips and six species are newly placed in synonymy: Thrips hawaiiensis (Morgan) (= Thrips exilicornis Hood from Africa); Thrips palmi Karny (= leucadophilus Priesner from Sudan); Thrips brunneus Anan. & Jaga. ( =speratus zur Strassen from South West Africa); Thrips tabaci Lind.(= kallarensis (Anan.) from India); Thrips sumatrensis Priesner (= lucaenae Moulton from Guam); Thrips simplex (Morison) (= Taeniothrips quinani Moulton from South Africa). Isoneurothrips Bagnall is regarded as a synonym of Thrips , and Isothrips is treated as a synonym rather than as a sub-genus. Two nominal species, beharensis (Ram. & Marg.) and rostratus (Ram. & Marg.) are considered unrecognizable at present.     

Predatory effect of Coccinella septempunctata on Thrips tabaci and Trialeurodes vaporariorum

Abstract:  The predatory effect of adult ladybird Coccinella septempunctata L. on adults of thrips, Thrips tabaci Lindeman, and whiteflies, Trialeurodes vaporariorum (Westwood), was examined in controlled environment chambers, on tomato leaves, in transparent small plastic cages at proportions of 1/(10 + 10), 1/(20 + 20), 1/(30 + 30) and 1/(40 + 40) predator/number of thrips and whiteflies. We conclude that C. septempunctata could be used with success for the biological control of thrips and whiteflies in greenhouse crops, with almost the same effectiveness as for aphids, at predator/prey proportions near 1 : 30. Additionally, it was found a prey preference for T. tabaci in comparison with T. vaporariorum . According to the model used, effective predation is correlated with predator/prey ratio rather than to prey preference.     

Discrimination of reproductive forms of Thrips tabaci (Thysanoptera: Thripidae) by PCR with sequence specific primers

In agriculture, although it is important to identify species of pest insects, the morphological identification is often difficult. DNA genotyping is useful for the identification of species in morphologically indiscriminable species. Thrips tabaci (Lindeman) can be divided into two reproductive forms (arrhenotoky and thelytoky, each of which different in pesticide resistance) but morphological discrimination is not possible. Here, we establish a simple method to discriminate the strains based on their mitochondrial DNA sequences. Phylogenetic analysis including the T. tabaci and congeneric species provided ancestor sequences of each strain of T tabaci. Based on the ancestor sequences, we developed a primer set that include strain specific primers on sense strand and common primer on anti sense strand. Using this primer set, the strains of 196 individuals of T. tabaci were successfully assigned to each ofgenotypic forms. As the phylogeny and ancestor sequences were based on worldwide samples, this method will work well on most populations around the world.     

Biological control of thrips [Thysanoptera: Thripidae] on greenhouse cucumber byAmblyseius cucumeris

The predatory miteAmblyseius cucumeris (Oudemans) [Acarina: Phytoseiidae] was evaluated as a biological control forThrips tabaci Lindeman andFrankliniella occidentalis (Pergande) [Thysanoptera: Thripidae] on greenhouse grown seedless cucumber.A. cucumeris spread throughout the greenhouses and provided control of both species of thrips.A. cucumeris adults persisted on plants for 7 weeks in the virtual absence of prey, and increased numerically in response to increases in prey population. On the basis of these resultsA. cucumeris is recommended as a useful biological control forT. tabaci andF. occidentalis on greenhouse cucumber. Publication No. 361, Agassiz Research Station, Agriculture Canada, Agassiz, B.C. Canada VOM 1AO.     

西花蓟马与烟蓟马药剂敏感性的比较

采用浸叶法比较了外来入侵物种西花蓟马Frankliniella occidentalis(Pergande)与本地物种烟蓟马Thrips tabaci Lindeman对辛硫磷、毒死蜱、高效氯氰菊酯、多杀霉素、甲氨基阿维菌素苯甲酸盐和阿维菌素6种杀虫剂的敏感性。结果显示:西花蓟马对辛硫磷、毒死蜱和多杀霉素的敏感性均比烟蓟马明显要高,而高效氯氰菊酯和阿维菌素对烟蓟马则具有较高的毒力。多杀霉素对西花蓟马和烟蓟马的防治效果最好,在药剂浓度为0.5mg/L时,2种蓟马的校正死亡率均超过90%。     

Patterns of insecticide resistance in onion thrips (Thysanoptera: Thripidae) in onion fields in New York

To develop an insecticide resistance management program for onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), on onions (Allium spp.), we surveyed populations in commercial onion fields in New York and evaluated their susceptibility to the two most widely used classes of insecticides plus two new insecticides during 2003-2005. All insecticide evaluations were conducted using the Thrips Insecticide Bioassay System (TIBS). As in our surveys conducted during 2002-2003, there were large temporal and spatial variations in susceptibility to the pyrethroid lambda-cyhalothrin (Warrior) across onion-growing regions in 2003. New data indicate that the field rate of methomyl (Lannate LV) still provides control but that the genes for resistance to methomyl are present in some populations. Tests with the two new insecticides, acetamiprid (Assail 70 WP) and spinosad (SpinTor 2CS), indicated they provided > 85% mortality at the field rate. To determine the spatial variation in insecticide susceptibility within a region, a series of systematic assays were conducted with lambda-cyhalothrin and methomyl. In 2004 and 2005, our data indicated that the within-region spatial variation in susceptibility to lambda-cyhalothrin was not large at the field rate or for the 100 ppm rate of methomyl. In 2005, a year in which T. tabaci densities in most fields were much higher than in 2004, growers were unable to control T. tabaci in particular fields and attributed this lack of control to resistance. Yet, we found similar levels of high susceptibility in all fields when using TIBS. This finding suggests that resistance had not developed and that variation in control may have been due to other factors, such as localized higher populations, poor spray coverage, too much time between spray applications, or different onion varieties.