VIII International Symposium on Thysanoptera and Tospoviruses

Abstracts are listed in alphabetical order by the last name of the senior author.

Adkins S¹, Lewandowski DJ²

¹USDA-ARS, U.S. Horticultural Research Laboratory, 2001 South Rock Road, Fort Pierce, FL 34945, USA

²Department of Plant Pathology, University of Florida, Citrus Research and Education Center, Lake Alfred, FL 33850, USA.

Correspondence: sadkins@ushrl.ars.usda.gov

Tomato spotted wilt virus (TSWV) infects tomatoes and a wide range of other crops across temperate, subtropical and tropical regions throughout the world. A broad array of TSWV symptoms is observed on crops in Florida. In tomato foliage, for instance, necrotic ring and line patterns, necrotic spots, leaf rolling and leaf bronzing/purpling are common. This variability in symptoms may reflect diversity in the virus population. A study of the TSWV population in Florida was initiated in an effort to examine its diversity. A better understanding of the TSWV population structure will aid development of rational disease management strategies.

Arévalo HA, Liburd OE

Entomology and Nematology Department, University of Florida, Gainesville, FL 32611 USA.

Correspondence: aleareva@ufl.edu

United States is the largest producer of blueberries with an approximate value of 137,000 tons/year. This represents 65% of the total production worldwide. Early-season blueberries produced only in Florida and southern Georgia between the months of April and May have prices that can be three to five times higher than regular-season blueberries in northern US states. Flower-thrips from the genus Frankliniella are considered as key pests for early-season blueberries in the southeastern United States. Based on observations conducted between 2003 and 2005 during the blueberry flowering season, we determined that the predominant flower-thrips species of blueberries in Florida is F. bispinosa (Morgan), and in southeastern Georgia is F. tritici (Fitch). Other species present include F. occidentalis (Pergande), F. fusca (Hinds), Thrips hawaiiensis (Morgan), and T. pini Uzel. A series of observations in oviposition behavior and populations dynamics were made in Southern highbush (Vaccinium corymbosum x V. darrowi) and Rabbiteye blueberry (V. ashei), the two main species grown in Florida and Southern Georgia. The main objective of this work was to understand the oviposition preferences, movement and distribution of flower-thrips in early-season blueberries, with the ultimate goal of establishing an IPM program for controlling thrips. The results of our observations show a significantly higher number of thrips emerging from flower petals than from ovaries, styles or fruits (F = 19.16; df = 3, 158; P < 0.0001) of flowers collected in the field. This indicates a preference to oviposit on the petals than in any other tissues of the blueberry flower. There were no significant differences in thrips emergence between the two blueberry species evaluated, Rabbiteye (3.11 ± 1.2) and Southern Highbush (4.0 ± 1.5) (F = 0.01, df = 1,38; P = 0.93). At the beginning of the season when the flowers begin to open, thrips infestation is very sporadic and populations are relatively low. Flower-thrips clusters or “hot-spots” are defined 7 days after flowers begin to open. Thrips gradually increase in area and population for approximately 2 weeks. Thrips populations in these “hot spots” increase exponentially for approximately 14 days, until 90% of the flowers are open, then it declines until the thrips virtually disappear at petal fall. At this time only fruits are standing in the field illustrating a correlation with the phenology of the flowers. Based on this time-line and observations conducted in the laboratory, thrips may have at least one generation on blueberry flowers, affecting fruit quality by leaving scars from feeding, and injuring reproductive tissues by ovipositing, and emerging from the ovary. Thrips also affect and quantity of blueberries by dehydrating flowers that have been severely attacked.

Bhanupriya M¹, Srinivasulu P², Zehr UB¹, Ravi KS¹

¹Mahyco Research Center, Jalna-Aurangabad Road, Dawalwadi, Jalna-431203, Maharashtra, India.

²Department of Virology, S.V.University, Tirupati-517502, Andhra Pradesh, India

Correspondence: Ravi.Kankanallu@mahyco.com

Tospoviruses are one of the major constraints in vegetable production next to geminiviruses in India. The spotted wilt in tomato, caused by peanut bud necrosis virus (PBNV) which is widely prevalent and it is one of the significant yield-limiting factors. Surveys were conducted during 2002–05 in the potential vegetable growing regions of Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu for the detection of tospoviruses and their natural occurrence. The incidence of spotted wilt in tomato varied from 2 to 87%. Field isolates showing typical spotted wilt and related symptoms was detected by DAC-ELISA using PBNV specific antisera, some of the hosts include tomato, chili, brinjal, peanut, greengram, soybean, blackgram, carrot, field bean and watermelon. In order to establish the genetic diversity among tospovirus isolates, the representative virus isolates were initially purified in cowpea cv. C-152 and characterized the NP gene sequences. Molecular analysis showed that the NP gene sequences from 36 isolates among nine different crops revealed very high degree of homology ie 94–99% at nucleotide and 94.9–100% at amino acid level with the reference Indian PBNV sequence (U27809). The characterized PBNV isolates were also compared with the other tospovirus members which include watermelon bud necrosis virus (WBNV) and watermelon silver mottle virus, which shares 79.8–81.3% and 83.7–87.3% homology at nucleotide & amino acid level respectively. In addition to PBNV, three other distinct tospoviruses viz., WBNV, IYSV and peanut yellow spot virus isolates were encountered in watermelon, onion and peanut crops respectively.

Beaudoin AL, Kennedy GG

North Carolina State University, Department of Entomology, Raleigh, NC, USA.

Correspondence: alparodi@ncsu.edu

Spatial dispersal patterns of Frankliniella fusca (Thripidae), a vector of the tomato spotted wilt virus (TSWV), are not well understood. A study was conducted in three fields of bare soil in North Carolina to determine if the number of adult F. fusca caught on yellow, sticky traps exhibited a gradient varying with distance from a natural weedy source containing known hosts of F. fusca. Yellow, sticky aerial traps were placed 0.76 meters above the soil in recently disked fields. The traps were placed in a grid and the nearest potential sources of thrips on one or more edges of each field were identified. Traps remained in the field for one week and were collected before any vegetation emerged in the field. The number of F. fusca per trap was determined. The data revealed no gradients in numbers of thrips per trap over distances of up to 500 meters from a potential thrips source. In late July, a second study was conducted in three tobacco fields to determine if TSWV incidence exhibited a gradient with changes in distance from potential thrips and TSWV sources. Rows of tobacco plants were visually scored for the presence of TSWV every 15.24 meters, resulting in a grid. The nearest potential sources of thrips and TSWV were identified. No gradient in TSWV incidence was found in distances of up to 200 meters. These studies suggest that management of weed hosts of TSWV around field margins may not be an effective strategy to reduce spread of tomato spotted wilt virus into susceptible crops.

Belliure B ^1,2, Janssen A¹, Sabelis MW¹

¹IBED, Institute for Biodiversity and Ecosystem Dynamics, Section Population Biology. University of Amsterdam. PO Box 94084 1090 GB Amsterdam, The Netherlands

²Present address: IVIA, Valencian Institute for Agricultural Research, Entomology Unit. Apartado Oficial, 46113 Moncada (Valencia), Spain.

Correspondence: belliure@ivia.es

Plants are the target of various attackers, such as herbivorous arthropods and plant pathogens. Constitutive defences to these attacks (spines, hard cuticle, etc.) are costly when attackers are not present. Therefore, many plants possess inducible defences that are switched on only upon attack. Induced responses to herbivory are mediated via several metabolic pathways, in particular the Jasmonic Acid (JA) pathway. Defences induced by herbivores involve changes in the quality of attacked plants that affect the fitness of the herbivore (direct defence), and the emission of plant volatiles that attract natural enemies of the herbivore towards attacked plants (indirect defence). As a result, herbivore-induced plants become hosts of inferior quality for herbivorous arthropods, and are therefore less attractive for conspecific or heterospecific herbivores. Pathogens induce anti-pathogen resistance in plants through the Salicylic Acid (SA) pathway. Anti-herbivore and anti-pathogen defensive pathways cross talk in several plant-pathogen systems: up-regulation of the SA pathway results in down-regulation of the JA pathway. This negative cross talk can be exploited by vectors of pathogens, because induction of the anti-pathogen pathway reduces investment of the plant in anti-herbivore defence. In turn, vector-borne pathogens receive a benefit from this cross talk because a pathogen-infected plant with a reduced anti-herbivore defence represents a good host plant for the herbivorous vector of the pathogen. This is the case for Tospoviruses that are vectored by thrips. Thrips induce anti-herbivore defences in the plants that are detrimental for thrips. However, adult thrips are often attracted to tospovirus-infected plants, in spite of these being induced by thrips. Recent research showed that Frankliniella occidentalis actually benefited from attking plants infected with Tomato spotted wilt virus; survival and developmental rates of thrips larvae were as high on virus-induced (and thus also herbivore-induced) plants as on clean, uninduced plants, and higher than on plants with thrips damage. This is in agreement with the described JA/SA cross-talk. The interaction between the two pathways has several ecological implications. We show that spider mites, another herbivorous arthropod that do not vector the virus, can benefit from plants being infected with the virus. However, this benefit is not due to the negative effect of the virus on the defensive response of the plants to thrips damage. Furthermore, we show that the shorter developmental rate of thrips larvae that develop on plants with virus results in reduced vulnerability to attacks by at least some of its natural enemies. We propose that mechanisms to reduce direct and indirect plant defences against vectors may have evolved in vector-borne plant pathogens, thereby promoting spread of the pathogen.

Bennison J¹, Maulden K¹, Tomiczek M¹, Morris J², Barker I², Boonham N², Spence N²

¹ADAS Boxworth, Boxworth,CB23 4NN,UK.

²Central Science Laboratory, Sand Hutton, York, Y041 1LZ, UK.

Correspondence: jude.bennison@adas.co.uk

Some of the major UK growers of chrysanthemums and other protected ornamental crops are using entomopathogenic nematodes (epns) for biological control of western flower thrips (WFT), Frankliniella occidentalis. Weekly foliar sprays of Steinernema feltiae (‘Nemasys F’ ®) are used throughout the life of the crop and these generally give good control of thrips. However, use of epns for thrips control is expensive and this is inhibiting more growers from adopting the technique. In addition, control on chrysanthemums can sometimes be inadequate during the summer when thrips pressure is high. Current Defra-funded research aims to fill gaps in knowledge on how epns control WFT populations and whether this control is sufficient to reduce the spread and severity of Tomato spotted wilt virus (TSWV) on chrysanthemums. Results indicate that epns reaching the growing medium during foliar application could play an important role in WFT control by killing the ground-dwelling thrips life stages. This information should enable the development of techniques to make the use of epns more effective and economic. In a glasshouse experiment, weekly foliar applications of ‘Nemasys F’ were made to two sequential crops of pot chrysanthemums, cv. ‘Swing Time’, which had been infested with viruliferous WFT larvae. The nematodes reduced mean numbers of WFT per plant, delayed plant infection with TSWV and reduced the symptom expression of TSWV.

Ben-Yakir D, Jasrotia P, Chen M

Entomology Department, Institute of Plant Protection, ARO, The Volcani Center, P.O. Box 6, Bet-Dagan, Israel 50250.

Correspondence: benyak@volcani.agri.gov.il

We used pole traps to determine the annual and daily variations in the migration activity of Thrips tabaci and Frankliniella occidentalis. The pole traps were 3m high and were placed near walk-in tunnels and in open fields at 4 different geographical locations in Israel. Thrips populations were peaked between April and June depending on the environmental conditions at each location. Twice as many thrips were caught on the pole at the eastern entrance of the tunnels than at the western entrance. At almost all sits, the highest numbers of thrips were caught on the eastern side of the poles (40–50%) and the lowest numbers were caught on the western side (10–20%). Annually, about 75% of the thrips were caught before noon time, and about 50% were caught below the height of 70 cm. In preliminary trials in which the eastern entrance of the tunnel was covered, it reduced thrips entry significantly with only a slight effect on ventilation efficacy. This information can be used to reduce the risk of thrips entry into greenhouses. Rabbit immunoglobulin G (R-IgG) was used successfully as an external mark for thrips. Females of both Thrips tabaci and Frankliniella occidentalis were marked with R-IgG solution (1 mg/ml water with 1% Tween 20) by the contact exposure method. Determining the retention of the mark was done by running the rinsing solutions of individual thrips in an enzyme–linked immunosorbant assay (ELISA). The sandwich ELISA method was used with an additional biotin-avidin step that increased the assay’s sensitivity by 3–5 folds. When marked thrips were kept in the laboratory on bean pods they all scored positive 6 days after marking (DAM). All marked thrips scored positive 2 DAM when kept in the laboratory on detached marigold flowers. When marked and unmarked thrips were placed together on these flowers some mark had transferred and 10–20% of the unmarked thrips turned positive. Under field conditions, a gradual decrease in the mean optical density levels of the marked thrips was observed over time. On sticky pole traps, 100%, 85% and 15% of the marked T. tabaci scored positive by the 3rd, 6th and 9th DAM, respectively. Under the same conditions 100% and 15% of the marked F. occidentalis scored positive by the 6th and 9th DAM, respectively. Similar rates of positive scores were recorded for marked T. tabaci kept on chive plants for 6 DAM. The retention of the R-IgG mark decreased significantly under conditions of wetness and high humidity. The suitability of this marking method for dispersal studies of these important pests need to be evaluated now.

Bertrand P, Culbreath A

Department of Plant Pathology, The University of Georgia.

Correspondence: bertrand@uga.edu

The spatial development of spotted wilt has been studied in tobacco and peanut. Tobacco data from trials conducted between 1989–2004 comprising ~2200 individual reps with > 100 plants was subjected to ordinary runs analysis. The results were tabulated by disease incidence classes ranging from <11% – >71% at 10% intervals. In the four disease incidence classes ranging from <11% – 40.9% aggregation occurred in 10–13% of the cases. In the four disease incidence classes from 41% – >71% there was a steadyilar conclusion for both peanut and tobacco. Secondary infection is biologically possible in both crops however data from spatial analysis and other trials suggest that the majority of visible disease results from primary infection.

Scott Brown AS, Veitch NC, Simmonds MJS

Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK.

Correspondence: a.scott-brown@rbgkew.org.uk

One of the primary aims of the Royal Botanic Gardens (RBG), Kew, is to conserve its unique living collections of 33,000 plant species, many of which are classified as rare and endangered. Thrips have persisted as a threat to plant species contained in the display glasshouses since the introduction of IPM programs at Kew in the early 1990s. The genetic and phenotypic diversity of plants housed together in artificial conditions has lowered the efficiency of biological control predators which have been used successfully to control invasive thrips species on protected crops in the commercial horticultural sector. We have monitored and documented plants among the collections in the Temperate House, RBG Kew, as hosts or non-hosts to two invasive thrips; Heliothrips haemorrhoidalis (Bouché), and Frankliniella occidentalis (Pergande) and further investigations have highlighted species of host plants where the effectiveness of the predators; Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Orius laevigatus (Fieber) were significantly reduced. This study aims to highlight the morphological and chemical differences among the foliage of the hosts and non-hosts of H. haemorrhoidalis. Scanning electron microscope techniques were used to describe the morphology of the leaf surface of 19 species in order to help identify which morphological features could play a role in the selection of plant species by thrips from among a diverse botanical collection. The results showed H. haemorrhoidalis had a preference for species with leaves that were coriaceous, with one or both surfaces being smooth. Plants evading these thrips commonly possessed glandular trichomes and waxes present on the surfaces of leaves were observed to be of dense, non-uniform forms, thus potentially disrupting feeding and oviposition of H. haemorrhoidalis. In addition, detailed analysis of the phytochemical profiles of the leaves of non-hosts are in progress to identify which groups of compounds deter thrips, and which compounds present in hosts may result in a decrease in efficiency of the introduced predators. Initial studies have focused on the profiles of two non-hosts of H. haemorrhoidalis and several isolated compounds present in the foliage of these species have shown levels of activity against immature stages of F. occidentalis in controlled bioassay tests. Evaluating the roles of morphological and chemical characteristics of non-host plants in plant-thrips-predator interactions can serve to advance our methods in controlling thrips pests in all sectors of Horticulture.

Campbell LR¹, Webb C ², Westervelt L³

¹Department of Entomology, Kansas State University, Manhattan KS 66506.

²USDA, APHIS, PPQ, Department of Plant Pathology, Kansas State University, Manhattan KS 66506.

³Department of Horticulture, Forestry and Recreation Resources, Kansas State University, Manhattan KS 66506.

Correspondence: lcambel@ksu.edu

Kansas State University has an active Horticultural Therapy program and teaching programs in Plant Pathology, Horticulture, Forestry and Master Gardener programs. These courses all contain a hands-on training component, which takes place in the Throckmorton Greenhouse Complex. This results in increased human traffic and plant movement between the greenhouses. These activities increase the chance for thrips and their vectoring of Tomato Spotted Wilt Virus (TSWV) and Impatient Necrotic Spot Virus (INSV). On-going long term experiments, some involving tomatoes and other virus-susceptible plants, are also located in the complex. In addition, the K-State Gardens, located adjacent to the greenhouse complex, are a major tourist attraction and displays many tospovirus-susceptible plant species. Early in 2004, bedding plants in the Throckmorton Greenhouse Complex showed symptoms indicative of tospovirus infections. Initial testing using Immuno Strips (Agdia Corp.) verified TSWV/INSV in 4 of 22 plants. Funding was acquired with the purpose of developing and implementing policy to control tospovirus in the K-State Horticulture, Forestry & Recreation Resources (HFRR) greenhouses. Totally, 677 plants were sampled from 16 greenhouses, with 111 (16.39%) testing positive. These included 47 species from 29 families, with 23 species not found on other host lists. From this work, greenhouse management policies have been instituted. Weekly monitoring with sticky cards and elimination of infected plant material will control future tospovirus outbreaks.

Casey C, Sutliff-ShipleyS

Department of Entomology, North Carolina State University, Raleigh, NC 27695, USA.

Correspondence: chris_casey@ncsu.edu

The state of North Carolina has the fourth largest ornamental horticulture industry in the U.S., valued at about $1billion per year. Thrips and tospoviruses cause significant losses for greenhouse flower growers in North Carolina. In greenhouses the predominant virus is impatiens necrotic spot virus (INSV), although mixed infections with TSWV may be present. The western flower thrips, Frankliniella occidentalis, is considered to be the most important vector. A priority for improved greenhouse INSV management is some type of early warning system that would alert growers to the presence of infected thrips before crop symptoms are seen. Indicator plants develop characteristic symptoms within a few days after feeding by viruliferous thrips and serve as an alert to their presence. Since this system will only be effective if the indicator plant is more attractive to the viruliferous thrips than the crops they are intended to protect, we evaluated the relative attractiveness of two indicator plants, petunia and fava bean, and several greenhouse crops, to viruliferous F. occidentalis. Differences between indicator plants species in attractiveness were observed, and in some cases the crop plant was more attractive to thrips than the indicator. Since understanding thrips movement is key to understanding how epidemics develop, we also examined how pesticides might stimulate thrips movement and disease spread. If a pesticide is distasteful (i.e. repellent) a short tasting probe may stimulate vector movement without providing a lethal dose. Common greenhouse pesticides used for thrips and weed control were found to be repellent to F. occidentalis.

Chanbusarakum L, Ullman D

University of California-Davis, Department of Entomology, One Shields Avenue, Davis, CA 95616.

Correspondence: ljchan@ucdavis.edu

Symbiotic bacteria often have a complex association with their host, be it human or arthropod. Many insects possess symbionts, though it is often difficult to determine the intricacies of their relationships. In one such case, facultative bacteria have been discovered in the hindgut of a major crop pest and virus vector, the Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). The bacteria can be cultured outside thrips and are horizontally transmitted among WFT. Several thrips bacterial isolates have been studied in the Netherlands. Molecular data indicated thrips symbionts were similar to Escherichia coli, though biochemical properties suggested these microbes might actually be most similar to Erwinia. We focused on the bacterial flora of thrips originating from the Hawaiian Islands. Phenotypic data show that bacteria from thrips originating in the Hawaiian Islands and Netherlands were very similar. Molecular phylogeny based on the 16s rRNA gene suggested 2 separate groups of thrips bacteria were present in isolates from both geographic regions. One of the groups fell out closely with some Erwinia; however, bootstrap values for this classification were very low. Sound bootstrap values were not found for any of the relationships for the second group. The similarity between the microbes from different thrips in different locations and raised on different plant material suggest that the relationship between the bacteria and WFT are relatively stable and are not incidental infections arising from their environment.

Ciuffo M, Pacifico D, Turina M

Istituto di Virologia Vegetale, CNR, Torino 10135, Italy.

Correspondence: m.ciuffo@ivv.cnr.it

We detected a consistent different phenotype on Nicotiana benthamiana and N. tabacum between the Br01 isolate and the Italian isolate p272. Based on the phenotype of a reassortant strain carrying the S genomic segment of p272, and the M and L genomic segments from strain Br01, we concluded that the small segment of Br01 is necessary for eliciting lethal necrosis on N. benthamiana and local necrotic lesions on N. tabacum. The aim of this work was to evaluate if the nucleocapsid and non-structural small proteins encoded by the small genomic segment of strain Br01 were able to cause the distinctive symptoms, alone or in combination. The two allelic variants (the Br01 and p272) of each protein were transiently expressed in planta through agroinfiltration. Symptoms were monitored in order to detect reaction specific to the Br01 alleles. As a positive control for a viral protein causing lethal necrosis and necrotic local lesion, we infiltrated p19 of Tomato bushy stunt virus (TBSV); as negative control, the protein green fluorescent protein was inserted in the pBin61 vector. Accumulation of nucleocapsid and non-structural small proteins were monitored through western blot analysis. Green fluorescent protein accumulation was monitored visually under UV light observation. All the different alleles of the nucleocapsid and NSs proteins readily accumulated in the infiltrated N. benthamiana and N. tabacum leaves; no necrotic reaction was observed in any of the single or combined agro-infiltration. A necrotic response was observed when p19 protein was infiltrated in both N. benthamiana and N. tabacum. Our results suggest that non-structural small proteins Br01 and N Br01 cannot cause a necrotic response alone or in combination. Our hypothesis involves the requirement of different regions of the M and L segmentsof the genome.

Collins DW, Walsh K, Boonham N, Glover R, Barker I

Central Science Laboratory, Sand Hutton, York YO41 1LZ, United Kingdom.

Correspondence: dom.collins@csl.gov.uk

The polyphagous pest Thrips palmi Karny has become a species of major quarantine concern, often intercepted on plant material in international trade. The ability to rapidly identify the species is a critical factor that will help determine the success of any campaign to prevent its establishment in Europe. Confirmed morphological identification to species is limited to the adult thrips, yet quarantine diagnostic laboratories frequently have to make identifications with only larvae available, often with perishable commodities at stake. In this study, RAPD analysis was performed to identify 19 putative SCAR markers, which were screened by southern blot analysis; one marker was sequenced and a real-time PCR (TaqMan) assay developed (Walsh K et al. 2005. Journal of Applied Entomology 129: 272–279). The assay was screened against 21 thrips species including 10 other species of the genus Thrips and found to be specific to T. palmi. The speed, specificity, simplicity and robustness of the assay are all reasons why a real-time PCR format was selected for specific use as a quarantine entomology diagnostic tool in preference to other available molecular techniques. The use of a Smart Cycler II TD (Cepheid) offers the possibility of further reducing the total time of this assay to as little as 45 minutes, as well as the potential for on-site testing of samples at a suspected outbreak site or at a port-of-entry. The assay was designed to complement morphological identification of thrips, not to replace it. Numerous different species of thrips have been found in trade, both major pest species and some quite obscure ones. Morphological expertise will continue to be required to deal with the complexity and range of identification work required. Nevertheless, the development of molecular tools of ever increasing speed and scope offer tools for the future that will further increase the efficiency of quarantine diagnostic laboratories. To that end, the cytochrome oxidase I gene from those thrips species and populations used to produce this assay have been sequenced and analyzed as the first step towards the production of a microarray protocol with the ultimate aim of producing an assay that offers simultaneous screening of numerous thrips species in a user-friendly format.

Connell S¹, Wright S¹, Csinos A¹, Gitaitis R¹, Nischwitz C¹, Stephenson M², Mullis S¹

¹Department of Plant Pathology, University of Georgia, P.O.Box 748, Tifton GA 31793.

²Crop and Soil Sciences, University of Georgia, P.O. Box 748, Tifton, GA 31793

Correspondence: spotwilt@uga.edu

Tomato spotted wilt virus (TSWV) has caused severe losses in tobacco in Georgia for approximately 15 years. Although much has been learned in that time, one aspect not clearly documented was the intra-plant distribution of TSWV. In previous studies, virus detected in roots was thought to be redistributed throughout the plant. This study presents a further evaluation of virus distribution in individual tobacco plants. At 8 weeks post transplanting during the 2005 growing season, root tissues from ninety non-symptomatic N. tabacum L. variety K-326 plants were tested for TSWV by DAS-ELISA (Agdia Inc., Elkhart, IN). Ten infected and 10 healthy plants were flagged for further analysis. Leaves were numbered sequentially from oldest to youngest on each plant and 100 mg tissue samples were collected bi-weekly for 3 wks and tested by DAS-ELISA. Within this period, TSWV was found more frequently in the oldest and youngest leaves. Plants with roots testing positive initially had the highest frequency of old and new leaf infections, whereas, plants initially testing negative primarily had TSWV in younger leaves with a subsequent lower frequency of TSWV in roots. Symptom expression did not necessarily follow this infection observation. It is not known if two separate inoculation periods, plant physiology, leaf size, virus titer or some other factor is responsible for this pattern. These data suggest that when testing for TSWV in tobacco, samples should be taken from multiple sources (leaves of various ages as well as roots) to increase the probability of detecting an infected plant.

Crespi BJ, Morris DC, Mound LA

CSIRO Entomology, Canberra, Australia.

Correspondence: swmullis@uga.edu, Laurence.Mound@csiro.au

A single lineage of leaf-feeding Thysanoptera Phlaeothripinae has radiated solely on the plant genus Acacia in Australia into more than 250 species. The morphological diversity of these thrips is not closely correlated with their phylogenetic relationships as indicated by molecular studies using the genes CO1, 16S, EF1alpha and wingless. Molecular data indicates that behavioral character states are more strongly conserved than some morphological character states, the structural diversity within the kleptoparasitic thrips lineag being particularly high.

Csinos AS¹, Laska JE ¹, Mullis SW ¹, Stephenson MG ², LaHue SS ³, Nischwitz C ¹

¹University of Georgia, Dept. of Plant Pathology, Coastal Plain Experiment Station, Tifton, GA 31794

² University of Georgia, Dept. of Crop and Soil Science, Coastal Plain Experiment Station, Tifton, GA 31794

³ University of Georgia, Field Research Services, Coastal Plain Experiment Station, Tifton, GA 31794

Correspondence: csinos@tifton.uga.edu; nisc5708@uidaho.edu

Tomato spotted wilt virus (TWSV) continues to be a serious problem in tobacco in Georgia. In 2003, about 40% of the tobacco crop in Georgia was infected. Both Actigard and Admire have shown to be effective against TWSV and reduce incidence. In this study the effect of different combinations and rates of Actigard and Admire as well as pre-plant and post-plant applications of the chemicals on TWSV incidence were tested. The treatments included an untreated control as well as a transgenic standard. A randomized complete block design was used consisting of single row plots that were repeated five times using K-326 fluecured tobacco. The plots were set up in fields at the Coastal Plain Experiment Station. Of the 16 different treatment combinations tested, twelve significantly reduced the percentage of symptomatic plants. The lowest percentages of symptomatic plants and of plants killed by TWSV were achieved by pre-plant treatments with Actigard and Admire plus post-plant treatments with Actigard that included an application 28 days after planting. Several treatments that included post-plant applications resulted in significantly higher yields compared to greenhouse application of Actigard and Admire alone. The two best treatments which consisted of pre-plant applications of Actigard and Admire and either one (28 days after planting) or three post-plant applications of Actigard were within 300lbs./A yield difference compared to the non-diseased transgenic standard and had over 1300lbs./A higher yield compared to the untreated control.

Culbreath AK, Todd JW, Brown SL

The University of Georgia, Tifton Campus, P.O. Box 748, Tifton, GA 31793-0748

Correspondence: spotwilt@tifton.uga.edu

Tomato spotted wilt caused by thrips-vectored Tomato spotted wilt virus (TSWV) is a very serious problem in peanut (Arachis hypogaea L.) production in Georgia and the southeastern U.S. TSWV and the thrips, Frankliniella fusca and Frankliniella occidentalis that vector the virus present a difficult and complicated challenge from both epidemiological and disease management perspectives. Simply controlling the vectors with insecticides has seldom resulted in significant suppression of spotted wilt. Currently there is no single measure can provide adequate control of spotted wilt where severe epidemics occur. However, integrated management systems, using cultivars with moderate to high levels of field resistance, and suppressive chemical and cultural practices, have been developed and successfully deployed for minimizing losses to this disease. Adoption of some form of integrated management regime has been extensive and rapid in peanut producing areas of the U.S. where spotted is a problem. Although complete control of spotted wilt has seldom been achieved, integrated management practices have had a huge positive impact on peanut production in the presence of TSWV. The development of a spotted risk assessment index has aided greatly in relaying the importance of using an integrated approach for spotted wilt management. Natural field resistance appears to have the most potential for improving management of spotted wilt in peanut. New cultivars with high levels of field resistance have been developed and should greatly enhance management of spotted wilt as they are adopted. Breeding lines with even greater levels of field resistance than available in current cultivars have also been developed and are being increased for possible release as cultivars.

Davidson M, Teulon D

New Zealand Institute for Crop & Food Research Limited, Private Bag 4704, Christchurch, New Zealand

Thrips are weak fliers. After take off, thrips can be picked up by air currents flowing at strengths beyond their ability to fly against. Why do thrips launch themselves into such air currents? Likewise, what triggers them to drop out of the air currents? We have been investigating factors that may influence Western flower thrips’ take off and subsequent landing. In a wind tunnel females starved for at least 4 hours were more likely to fly than those not starved. The age of female thrips did not affect the proportion to fly in a wind tunnel, however a larger proportion of older thrips (13 days old) landed on a yellow sticky trap than younger thrips (3 days old). The concentration of a volatile compound affected the proportion of thrips to fly in a wind tunnel, with fewer flying in the presence of 1 ml of p-anisaldehyde compared to 0.5 ml. Field trials were undertaken using water traps surrounding a central trap baited with a volatile compound known to elicit a positive response in New Zealand flower thrips or onion thrips. The highest numbers of thrips were recorded in the baited trap with decreasing numbers in unbaited traps positioned within 2 m downwind of the central trap. The implications of these results in relation to thrips’ use of olfactory and visual cues, and thrips’ dispersal are discussed.

Dublon IAN, Hamilton JGC, Kirk WDJ

School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK.

Correspondence: i.a.n.dublon@keele.ac.uk

Frankliniella occidentalis (Pergande) is an established horticultural pest with a ubiquitous distribution. Its thigmotropic behaviour makes it difficult to control with insecticides and resistance is present in many strains. Two compounds, (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, isolated from the head-space of male F. occidentalis have been identified recently (Hamilton et al. 2005) and evidence thus far suggests that one of these compounds could be used for monitoring or mass trapping. The behavioral effects of these components on female and male F. occidentalis need to be investigated further in a laboratory environment. Y-tube bioassays only allow for the observation of a limited walking response. Alternative bioassays are therefore required to examine other responses, such as flight. Currently there are very few ways of bioassaying the flight response of thrips to specific semiochemicals within a laboratory without using a full-scale wind tunnel. Data are presented for the results of bioassays of the flight responses of adult female F. occidentalis to geraniol (trans-3,7-dimethyl-2,6-octadien-1-ol) using a novel twin-chamber moving-air bioassay. This compound is known to attract F. occidentalis in flight. It is hoped to use this working assay with the male-produced compounds. (Hamilton JGC. et al. 2005. Journal of Chemical Ecology 31: 1369–1379)

Funderburk J

North Florida Research and Education Center, University of Florida, 155 Research Road, Quincy, Florida 32351 USA.

Correspondence: jefunderburk@mail.ifas.ufl.edu

Two groups of natural enemies are important biological controls of flower thrips in field crops. Species of Orius (Hemiptera: Anthocoridae) suppress rapidly growing populations of flower thrips, and they persist once the prey populations are suppressed. Species of Thripinema (Tylenchida: Allantonematidae) are parasites of flower thrips that render the female hosts sterile. Adult male and female hosts that are parasitized feed less, thereby reducing primary spread of tospoviruses. Parasitism results in suppression of subsequent larval populations which also prevents secondary spread of tospovirus. Both groups of natural enemies are important factors in the reduction of populations of flower thrips throughout the landscape. There are many other natural enemies of thrips, but their importance in affecting population dynamics is not adequately understood. These natural enemies offer potential for management of thrips and tospoviruses.

E García-Cano¹, RO Resende² and E Moriones¹

¹Laboratorio Virología Vegetal, Estación Experimental "La Mayora", CSIC, Málaga, Spain

²Dept. Biologia Celular, Universidade de Brasília, CEP 70.910-970, Brasília-DF, Brazil.

Correspondence: rresende@unb.br

Tomato (Lycopersicon esculentum) is severely affected by viral diseases such as those caused by geminiviruses, tospoviruses, or criniviruses, which can result in significantly yield losses. Moreover, multiple viral infections are frequent found in nature with unpredictable pathological consequences. In fact, mixed infections between viruses may result in synergisms or antagonisms and can cause novel disease symptoms that could compromise virus control. In this work we have studied the possible interactions between the crinivirus (genus Crinivirus, family Closteroviridae) Tomato chlorosis virus (ToCV), and the tospovirus (genus Tospovirus, family Bunyaviridae) Tomato spotted wilt virus (TSWV), both viruses widely spread in the world. A tomato cultivar susceptible to both viruses, and a cultivar resistant to TSWV based on the Sw-5 gene but susceptible to ToCV, were used for inoculations. Simultaneous or delayed inoculations were assayed. Symptoms expression and virus accumulation were monitored in plants. A dramatic synergism was observed between ToCV and TSWV in plants of the susceptible cultivar after the simultaneous inoculation of both viruses, leading to a rapid death of plants. However, this synergistic effect was not observed in delayed inoculations. Interestingly, results indicate that the presence of ToCV in Sw-5-resistant plants previous to TSWV inoculation result in TSWV-resistance breaking. Financial support: CAPES, CSIC, MECD, FINATEC.

Garza R, Ruiz R, Ciomperlik M

USDA, APHIS, CPHST, Pest Detection and Diagnostic Management Laboratory, 22675 N. Moorefield Rd., Edinburg, TX 78541.

Correspondence: roxanne.e.garza@aphis.usda.gov

Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is a new invasive pest to the Caribbean, and poses a significant threat to US agriculture and trade in the western hemisphere. This pest thrips has recently invaded the Caribbean islands of St. Vincent, St. Lucia, and Trinidad (Ciomperlik MA, Seal D. 2004. USDA APHIS PPQ, Technical Report). Since 1984, USDA-APHIS inspectors at various ports of entry have reported finding live S. dorsalis a total of 89 times from imported plant materials of 48 plant taxa (USDA 2003. Port Information Network, PIN-309: quarantine status database. USDA, APHIS, PPQ). Scirtothrips dorsalis is a polyphagous pest that is widespread in habitat ranging from temperate to tropical climatic regions in Pakistan, Japan and Australia (Mound and Palmer 1981). It is a pest of economic importance in citrus growing regions of Asia, where feeding can cause significant leaf deformation, fruit damage and yield reductions. S. dorsalis is an economically important pest of chili pepper, castor, cotton, onion and other crops with physical damage that can range from stunting and wilting of young leaves and shoots to total defoliation, and potentially heavy crop loss (Ananthakrishnan 1993. Annual Review of Entomology 38: 71–92; CABI/EPPO 1997. Quarantine Pests for Europe, 2nd Ed). Traditional morphological identification of S. dorsalis requires slide mounting of specimens and knowledge of distinct characters visible by microscopic examination. The accurate identification of pest species is fundamental in pest management programs. Molecular based methods provide a means for the accurate identification of species. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach developed by Toda and Komazaki (2002, Bulletin of Entomological Research 92: 359–363) has been used to identify certain thrips species including S. dorsalis at our laboratory. In this study, PCR and DNA sequencing are being utilized to explore two regions of the mitochondrial gene, cytochrome oxidase I (COI). The DNA sequence data may provide information on the population genetic structure of S. dorsalis as well as its relationship to other thrips species. The DNA sequences will be analyzed to determine their potential for the development of species-specific molecular markers which will facilitate the design of real-time PCR assays. Real-time PCR will provide a fast and reliable method for the accurate identification of Scirtothrips dorsalis.

German TL

Department of Entomology, University of Wisconsin, Madison, WI 53706, USA.

Correspondence: tlg@entomology.wisc.edu

In 1984, Francki noted the similarity between Tomato spotted wilt virus (TSWV) and viruses in the family Bunyaviridae: a large group of membrane-bound, mostly arthropod-transmitted, animal-infecting viruses with tripartite negative-stranded RNA genomes. Data obtained in the last two decades elucidating the molecular biology of TSWV and the closely related Impatiens necrotic spot virus confirmed this observation and supplied the rational for the creation of the Tospovirus genus to include the plant-infecting, thrips-transmitted members of the family Bunyaviridae. Virions of TSWV, the type member of the family, are 80–120 nm pleomorphic particles with surface projections composed of two viral glycoproteins, G_N and G_C. The genome consists of three negative or ambisense ssRNAs designated S (2.9 kb), M (4.8 kb) and L (8.9 kb) with partially complementary terminal sequences that allow them to form a pseudocircular or panhandle conformation and likely serve as promoters for RNA synthesis. Each genomic RNA is encapsidated by multiple copies of the viral nucleocapsid protein (N) to form ribonucleocapsid structures (RNPs). The RNPs along with an estimated 20 copies of the L protein (RNA-dependent RNA polymerase) are enclosed in the viral membrane that is acquired during maturation at the Golgi. The ambisense S RNA encodes a 52.4 kDa nonstructural protein (NSs), in the viral (v) sense and the 29 kDa N protein in the viral complementary (vc) sense. The NSs protein is expressed from a v sense 1.7 kb subgenomic mRNA and the N protein from a 1.2 kb vc sense subgenomic RNA. The M RNA encodes a 33.6 kDa movement protein in the v sense and a 127.4 kDa precursor to G_N and G_C in the vc sense and relies on an expression strategy similar to that of the S RNA. The completely negative sense RNA contains a single open reading frame in the vc sense that is expressed from a nearly genome length mRNA. An additional 10–20 nucleotides of host origin are found at the 5’ ends of the viral N and NSs mRNAs providing evidence that TSWV uses the ends of host RNAs to acquire cap structures and direct transcription by means of a cap-snatching, typical of all segmented negative-sense RNA viruses. Details concerning the role of each viral protein in the infection cycle are beginning to emerge and recent work has suggested that, as expected, host proteins play a direct role as well. Future research directed towards understanding how proteins and nucleic acids interact to catalyze, regulate and target their activities will provide important new insights into the biology of these viruses.

Gitaitis R¹, Martinez N², Seebold K³, Stevenson K¹, Sanders H¹, Mullis S¹.

¹Univ. of Georgia, Tifton, GA; ²Lexington, KY, ³Univ. of KY, Lexington, KY USA.

Correspondence: dronion@uga.edu

Tissues from onion leaves infected with Tomato Spotted Wilt Virus (TSWV), or Iris Yellow Spot Virus (IYSV) and from tobacco infected with TSWV were triturated in phosphate-buffered saline (PBS) and 100 ul of the homogenate were spotted onto Whatman FTA cards and allowed to dry. Discs (2–3 mm diam) were punched from the FTA card and the bound nucleic acids on the paper discs served as a template for RT-PCR. Amplification products were detected by gel electrophoresis through a 1.0% agarose gel containing ethidium bromide in a 0.04M Tris–acetate 0.001M EDTA (TAE) buffer. Basically constructed of filter paper impregnated with proprietary chemicals that are activated by biological fluids, FTA cards can be used for a variety of purposes ranging from the rapid extraction of nucleic acids from ephemeral samples immediately under field conditions to archiving DNA and RNA samples and storing them at room temperature. Furthermore, since viruses are inactivated, FTA cards can be used for transportation of genetic material without the need for special biohazard precautions or plant pest permits.

D Gonsalves

ARS/USDA Pacific Basin Agricultural Research Center, 99 Aupuni Street, Suite 204, Hilo, Hawaii 96720, USA.

Correspondence: dgonsalves@pbarc.ars.usda.gov

Nearly 20 years ago, our laboratory embarked on developing virus resistant transgenic plants. The major viruses we focused on were papaya ringspot virus, tomato spotted wilt virus, and other vegetable viruses such as zucchini yellow mosaic, cucumber mosaic, and watermelon mosaic virus II. I will focus this talk on papaya ringspot virus and tospoviruses because they may present several lessons that will help to answer the question: Can Transgenic Virus Resistance Work in the Real World? The papaya work shows that transgenic virus resistance can work on a commercial scale and actually helped to save the papaya industry in Hawaii. Aside from the technical aspects, it also shows that timing and implementation of a transgenic product is important. One might say that the transgenic papaya was developed and commercialized before the ‘days of innocence’ with GMOs ended somewhere in 1998. To the present day, the papaya work also illustrates the type of forces or circumstances that affect the timely deployment of transgenic papaya outside of Hawaii. Relatively speaking, however, the papaya work did not shed as much light on the mechanism of transgenic virus resistance. In contrast, the work on tospoviruses did provide some insights on the mechanism and potential of transgenic tospovirus resistance. Given the range of crops that tospoviruses infect, one would expect that tospovirus resistance for commercial reasons might be a promising area of endeavor. However, I have not yet seen any signs that transgenic tospovirus resistance will be used commercially in the near future. Why is this? Is it because of technical difficulties? Is it because of the lack of will to do it? Or does the present GMO controversy suggest that the timing is not good for introducing tospovirus resistance to the real world? I will briefly discuss these aspects as they interrelate with my laboratory’s experience on papaya ringspot virus and tospoviruses.

Grout TG

Citrus Research International, PO Box 28, Nelspruit, 1200 South Africa.

Correspondence: tg@cri.co.za

South African citrus thrips (SACT), Scirtothrips aurantii Faure (Thripidae), is an indigenous pest of citrus in southern Africa and is often responsible for cosmetic damage to fruit that prevents the fruit from meeting export quality standards. Although the population density of SACT is largely determined by the availability of new, tender foliage (Gilbert MJ, Bedford ECG. 1998. In: Bedford ECG et al. editors. Citrus Pests in the Republic of South Africa. Second edition. 164–170. Republic of South Africa: Agricultural Research Council.), a complex of natural enemies helps to suppress the pest population. Some insect predators such as anthocorids, chrysopids and Thysanoptera are seldom abundant and levels of parasitism by Goetheana incerta Annecke are generally low. Predatory mites, and to a lesser extent, spiders, seem to be the most consistently abundant natural enemies both in the trees and in the soil below trees where SACT pupates. Little research has been conducted on non-target effects on spiders but recent research on the soil mite Androlaelaps sp. (Laelapidae) and earlier research on arboreal Euseius spp. (Phytoseiidae) (Grout TG, Richards GI.1992. Experimental & Applied Acarology 15: 199–204.; Grout TG et al. 1997. Experimental & Applied Acarology 21: 171–177) has enabled the selection of thripicides that are the least detrimental to these natural enemies. The efficacies of these and other biorational treatments were compared in the field with a view to finding the most effective but least disruptive thripicide. Application of insecticides via drip irrigation was also evaluated as a means of reducing non-target effects. Foliar treatments showing reasonable efficacy against SACT coupled with reduced mortality of predatory mites were: abamectin (0.00036% a.i.) plus oil (0.15%), spinosad (0.0072% a.i.) plus oil (0.3%), tartar emetic (0.199% a.i.) plus sugar (0.2%) and thiacloprid (0.0144% a.i.) plus oil (0.25%). Both dimethoate (36 g a.i./tree) and imidacloprid (2.1 g a.i./tree) showed promise as chemigation treatments.

Heinz KM, Chau A, Arthurs S

Department of Entomology; Texas A&M University, College Station, TX 77843.

Correspondence: kheinz@ag.tamu.edu

Control tactics deployed against key pests for the foundation for a crop’s pest management system around which all other control decisions must be coordinated. In the case of agriculture within protected systems, several species of thrips are commonly noted as the key pest for a particular cropping system. Management of these thrips species is built upon the best available research and education programs that address control foundations (proper identification of the key pest and how must it be controlled), stimuli for changing current management tactics (what forces are driving growers to move away from past practices), control combinations and their issues (what happens when two or more different kinds of control must be integrated), and techniques (what are the best available tool to accomplish the management goals). Protected culture provides a semi-permeable, replicated system for scientifically addressing the ecological and sociological factors influencing management systems. Examples from ornamentals and vegetables will be reviewed to identify factors leading to or impeding successful thrips management programs. A synthesis for systems-based approaches is developed for guiding future research objectives as well as in forming the foundation for novel thrips management programs.

Himmel P

Seminis Vegetable Seeds, Woodland, California, USA.

Correspondence: Phyllis.himmel@seminis.com

Tomatoes have been bred and selected for adaptation to specific growing areas for over 200 years and wild tomato species continue to be an important source of novel traits. Tomato spotted wilt causes yield losses in field and greenhouse tomato crops worldwide and unfortunately the efficacy of spray programs and cultural practices appears to be limited. Resistance to Tomato spotted wilt remains the most promising means of controlling this disease and can be found in Lycopersicon pimpinellifolium and L. peruvianum. Through wide interspecific crosses resistance has been introgressed into the cultivated tomato with good agronomic adaptability and commercial acceptability. Today, marker assisted selection for horticultural traits and disease resistance has streamlined the development of new commercial hybrids. The Seminis approach to breeding and selection for resistance, managing the resistance breaking isolates of Tomato spotted wilt, and the importance of combining resistance with key horticultural traits and marketing needs for a commercially successful product will be discussed.

Holmes ND, Kirk WDJ

School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK.

Correspondence: n.d.holmes@keele.ac.uk

The western flower thrips Frankliniella occidentalis (Pergande) is a major worldwide horticultural pest. It damages plants by feeding and by the transmission of tospoviruses. Crop quality suffers as a result, leading to financial losses for growers. Chemical control of F. occidentalis is difficult because insecticide resistance is widespread. In addition, adults and larvae secrete themselves into small, tight spaces, limiting the effectiveness of current chemical treatments. Automated tracking and analysis software (EthoVision ver 3.1, Noldus Information Technology, Wageningen) has been used to record the diel behavior patterns of adult female thrips indicating when they walked, fed and retreated into small spaces. The resultant behavior profiles indicated the period of greatest activity during a 24-hour cycle when thrips were most likely to come into contact with a treatment, enhancing the effects of control procedures.

Inoue T¹, Sakurai T²

¹United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan

²Department of Biology and Environmental Sciences, National Agricultural Research Center for Tohoku Region, Morioka 020-0198, Japan.

Correspondence: tsakurai@affrc.go.jp

Vector competence should be considered as the total transmission frequency during the potential transmission period from the onset of transmission to the vector death rather than the transmission rate for a certain period. The potential transmission period would be affected by vector longevity. If tospovirus infection has a negative effect on its vector longevity, the potential transmission period would shorten. In order to clarify the impact of infection of Tomato spotted wilt virus (TSWV) on the survival of two asexual Thrips tabaci populations, we compared i) the developmental rate, ii) the mortality before adult emergence and iii) the mortality during adult stage between virus exposed and non-exposed cohorts which were treated at young larval stage. No significant effects were observed in thrips developmental rate and the mortality rate during the developmental stage. However, the mortality trajectory showed that the age-specific mortality during adult stage was higher in virus exposed cohort than in non-exposed. We also estimated the potential transmission period from the mortality data and obtained the period of average 3.3 days in two tested populations. These results suggest that the potential transmission period shortened by TSWV infection may lead to low transmissibility of TSWV in asexual T. tabaci population.

Karadjova O, Krumov V

Plant Protection Institute, Kostinbrod 2230, Bulgaria.

Correspondence: oliakaradjova@abv.bg

Tobacco is a traditional field crop of great economic importance to Bulgaria. Tomato Spotted Wilt Virus (TSWV) was first reported in 1952 in Bulgaria and Thrips tabaci Lind was proved to be the only vector of the virus (Kovatchevsky I.1952. Bulletin Rastitelna Zashtita 3, 18–20; Ivancheva-Gabrovska. 1984. Studies on TSWV (Tomato Spotted Wilt Virus) in Bulgarian tobacco field. Doctoral dissertation, Plovdiv, Bulgaria; Dimitrov A. 1991. Biocenological studies on tobacco in Bulgaria and possibility for control of Thrips tabaci Lind. – the most important pest. Doctoral dissertation, Plovdiv, Bulgaria; Hristova D. et. al. 2001. Journal of Phytopathology 149, 1–5). Two different Th. tabaci populations – arrhenotokous (Th.t.1) and thelotokous (Th.t 2) were tested for their ability to transmit two TSWV isolates (BR-01 and GD from tobacco). DAS-ELISA was used to confirm the infection in individual thrips. The transmission efficiency of adult Th. tabaci was tested on petunia leaf discs (Wijkamp, I. 1995. Virus-vector relationships in the transmission of tospoviruses. Ph. D thesis, Wageningen, the Netherlands). Thrips and TSWV incidences were investigated in Bulgarian tobacco fields for a period of 50 years and the climatic conditions for every year were taken into account. The data analysis shows that TSWV epidemic has a 5–6 year interval of occurrence. The main outbreaks of TSWV were observed country wide in 1969 (57 %) and 1983 (53 %). Although the climatic conditions through these two years were favorable for both development of Th. tabaci and viral infection, during the remaining years no relation between TSWV epidemics and thrips infestation has been established. For example in 1972 there was 35% thrips infestation of tobacco plants, but TSWV infection was only 5%. The opposite phenomenon occurred in 1960 – 9% of thrips infestation corresponded to 23% of TSWV infection. Positive ELISA values were found only in the arrhenotokous population (Th.t.1). The average ELISA values were higher for TSWV –GD isolate, male individuals (OD = 0.377). Comparative laboratory studies for measuring of TSWV transmission efficiency of arrhenotokous and thelytokous populations have been conducted. Our investigation showed that the arrhenotokous population of Th. tabaci from tobacco is an efficient vector of TSWV (range from 2.08 to 39.58 %). The transmission rates of male specimens were higher than those of female ones. TSWV isolate GD from tobacco was transmitted more efficiently than BR-01. The telotokous population was not able to transmit both tested isolates.

Karadjova O¹, Krumov V¹, Nikolov P²

¹ Plant Protection Institute, 2230 Kostinbrod, Bulgaria

² National Service for Plant Protection, 55 Hr. Botev Blvd., Sofia, Bulgaria.

Correspondence: oliakaradjova@abv.bg

Since the Western Flower Thrips (Frankliniella occidentalis Perg.) was first reported in Bulgaria in 1991, it has become one of the most important greenhouse crop pests (Trenchev G, Karadjova O. 1992. Plant Protection Journal 3: 26–30; Karadjova O et al. 2003. Acta Entomologica Bulgarica. 9: 22–29). The first TSWV epidemic was recorded in 1993 in many greenhouses across the country (Hristova D et al. 2001. Journal of Phytopathology 149: 1–5). Until now, TSWV is the only tospovirus that has been found on vegetables and ornamental crops in Bulgaria, although INSV has been found on imported planting material especially from Israel and the Netherlands. The absence of INSV Tospovirus, also in ornamentals, indicates that at present the tospovirus population in Bulgaria is indigenous and not contaminated with strains from Western Europe (Hristova et al. 2001). Two different F. occidentalis populations (F.occ. 1 and F.occ. 2) and three TSWV isolates (BR-01, GD from tobacco and KR from greenhouse tomato) were used in this investigation. DAS-ELISA was used to confirm infection in individual thrips. The transmission efficiency of adult Th. tabaci was tested on petunia leaf discs (Wijkamp I. 1995. Virus-vector relationships in the transmission of tospoviruses. Ph. D thesis, Wageningen, the Netherlands). Positive ELISA values were detected in both F. occidentalis populations. The highest percent TSWV positive thrips was established for the combination F. occ. 2 - TSWV KR (Bulgarian greenhouse isolate from tomato). The lowest ELISA values were detected for F.occ.1 - TSWV isolate from tobacco (GD). Insect transmission tests were conducted with the same populations. Our tests demonstrated successful transmission of TSWV by both F. occidentalis populations. The highest transmission rate was observed for the combination F.occ. 2 – KR isolate (52.08%). Transmission efficiency of F.occ. 1 – TSWV BR-01 reached 27.08% and the lowest transmission was observed in F.occ. 1 – GD (6.25%). Results of virus transmission to leaf discs were correlated to the readings in ELISA.

Kennedy G

Department of Entomology, North Carolina State University, Raleigh, NC USA.

Correspondence: george_kennedy@ncsu.edu

This presentation will provide a brief overview of recent advances in our understanding of thrips population dynamics and Tomato spotted wilt virus (TSWV) epidemiology as they relate to currently available options for TSWV management. The constraints on TSWV management imposed by modern cropping systems will be discussed in an attempt to identify the essential attributes of viable management options for TSWV.

Kirk WDJ

School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK.

Correspondence: w.d.j.kirk@keele.ac.uk

Across northern Europe, thrips are popularly associated with thunderstorms. Although they fly mainly in fine weather, there is indirect evidence that they land when thunderstorms are near. The effect is most obvious for abundant species, such as cereal thrips. One hypothesis is that thrips cannot fly in rapidly changing electric fields that occur near thunderstorms, so they are forced to land (Kirk WDJ. 2004. Phytopathologica et Entomologica Hungarica 39: 131–136). Experiments are needed to test the effects of electric fields on the flight behavior of thrips.

Kirk WDJ

School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK.

Correspondence: w.d.j.kirk@keele.ac.uk

There is increasing evidence that chemical communication plays a major role in many aspects of the life of the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). This now includes research on an alarm pheromone produced by larvae and an aggregation pheromone produced by adult males, as well as research on responses to plant volatiles and related compounds. Since this species has only become the focus of research because it is a major pest, it is likely that chemical communication also plays a major role in the biology of many other species of thrips. Thus, a vast research field is opening up. Current developments in the chemical ecology of the western flower thrips and other thrips are reviewed, and possible future research directions and applied prospects are considered.

Kumm S, Moritz G

Martin-Luther-University Halle-Wittenberg, Developmental Biology, Domplatz 4, 06108 Halle, Germany.

Correspondence: sandra.kumm@zoologie.uni-halle.de

The last two decades revealed Wolbachia as one of the most widespread bacteria among arthropods. Bacteria of this genus are known to cause diverse reproductive manipulations in their hosts including cytoplasmic incompatibility, male killing, parthenogenesis, and feminization. In thrips females are usually diploid and males are haploid. The most common form of reproduction is arrhenotoky, but thrips also often reproduce by thelytoky. A couple of species are known to reproduce by thelytoky in some geographical areas, whereas the sex ratio values indicate arrhenotoky in other areas. Wolbachia was discovered in the thelytokous thrips species, Heliothrips haemorrhoidalis and Hercinothrips femoralis (Pintureau B et al. 1999. Annales de la Societe Entomologique de France 35: 416–420) and was proven to be responsible for thelytoky in Franklinothrips vespiformis (Arakaki N. et al. 2001. Proceedings of the Royal Society of London, Series B 268: 1011–1016). So far only thelytokous thrips species were tested. Therefore, in the present study we screened thrips species displaying different reproduction modes for the presence of Wolbachia using 16S rDNA and ftsZ gene primer. The thelytokous species Hercinothrips femoralis and Parthenothrips dracaenae possess Wolbachia and in H. femoralis Wolbachia was shown to be the reason for thelytokous reproduction since males were produced after antibiotic treatment. Males were also observed to copulate with females and spermathecae of females were filled with sperm. But it was not possible to generate an arrhenotokous line in H. femoralis. The arrhenotokous species Echinothrips americanus, Suocerathrips linguis, and Gynaikothrips ficorum also harbour Wolbachia, but the bacterium was not detected in Frankliniella occidentalis and Thrips tabaci. Neither thelytokous nor arrhenotokous populations of the latter species possess Wolbachia. Sequence analysis of three species, H. femoralis, P. dracaenae, and S. linguis, by direct sequencing confirmed the presence of Wolbachia, whereby all tested species are infected with different Wolbachia types. Antibiotic and heat treatment of thelytokous T. tabaci did not lead to male production and therefore bacteria are likely to exclude as being responsible for thelytoky in this species. Thus, it can be concluded that probably two different forms of thelytoky exist in Thysanoptera, one induced by microorganisms like in H. femoralis and a non-revertible (not induced by micro-organisms) like in T. tabaci. All positive tested species are no tospovirus vectors and species which do not possess the bacterium are known to act as tospovirus transmitters. Maybe there is some mechanism which protects tospovirus vectors from getting infected with Wolbachia or the opposite way around. It should be also proofed if and what influence Wolbachia has on arrhenotokous thrips species. Perhaps they also exhibit some kind of defence reaction against the bacterium suppressing the manipulation of reproduction.

Lovato FA¹, Nagata T, Ávila AC², Resende RO¹, Inoue-Nagata AK²

¹Departamento de Biologia Celular, UnB, Brasília, DF

²Embrapa Hortaliças, Brasília, DF.

Correspondence: alicenag@cnph.embrapa.br

Tomato spotted wilt virus (TSWV) causes a serious disease in plants worldwide. The three genomic RNA′s of TSWV encode three structural proteins (L, G1/G2 and N) and two non-structural proteins (NS_M and NS_S). Reaction to TSWV inoculation resembling the hypersensitive response (HR) has been previously reported in Capsicum chinense ′PI152225′ and ′PI159236′. The aim of this study was to identify the TSWV elicitor(s) protein(s) related to this HR-like response in C. chinense. For this purpose, the N, NS_M and NS_S genes of TSWV were cloned into the binary vector pgR107, based on Potato virus X (PVX) expression system via agroinoculation. Recombinant agrobacterium colonies transformed with the N, NS_M and NS_S gene constructs were inoculated into C. chinense ′PI159236′. After 10–15 days, typical symptoms of PVX appeared in the upper leaves of plants inoculated with the constructions PVX+N, PVX+NS_M and PVX+NS_S. ELISA and Western blot confirmed the N, NS_M and NS_S protein expression in inoculated plants. HR-like necrotic lesions were seen only in 'PI159236' infected with the construct PVX+N. The symptomatic leaves showed typical leaf abscission after 30–35 days. This result indicated that the N gene of TSWV is possibly the elicitor of the HR-like response in C. chinense. In addition, leaves of C. chinense, D. stramonium and N. benthamiana inoculated with the construction PVX+NS_S showed severe necrotic symptoms, suggesting an increase of PVX symptom expression caused by a possible synergism of PVX with the NS_S protein. Financial Support: CNPq, Embrapa, UnB, FINATEC.

Mahaffey L, Cranshaw W, Schwartz H

Department of Bioagricultural Sciences and Pest Management Colorado State University, Ft. Collins, CO 80523.

Correspondence: linda.mahaffey@colostate.edu

Thrips problems affecting onions in Colorado have increased greatly in recent years because of: 1) difficulties in control due to development of insecticide resistance; and 2) emergence of thrips-vectored Iris yellow spot virus as a new disease of the crop. In response, a wide range of studies are being conducted at Colorado State University to better understand seasonal biology of thrips associated with onion and identifying effective pest management practices. Onion thrips, Thrips tabaci, is the predominant species in all production areas followed by western flower thrips, F. occidentalis and F.schultzei. Over 95% of all thrips are T. tabaci in most areas, but F. occidentalis was present in high percentage (ca. 24%) in southwestern Colorado. Introduction of thrips on transplants grown in California, Arizona and Texas is a significant source of thrips with 57% (8/14) and 95% (21/22) of samples infested in 2004 and 2005, respectively. Thrips tabaci predominated but other species present were F. ewarti, F. occidentalis, and Scirothrips longipennis. The ratio of Thrips tabaci to Frankliniella spp. did not shift in fields with repeated history of pyrethroid use (lambda-cyhalothrin).

Margaria P, Turina M

Istituto di Virologia Vegetale, CNR, Torino 10135, Italy.

Correspondence: m.turina@ivv.cnr.it

Tomato spotted wilt virus (TSWV) (Tospovirus, Bunyaviridae) causes one of the most devastating diseases of pepper (Capsicum sp.) worldwide. The most effective and environmentally sound control strategy for this virus relies on the availability of resistant pepper cultivars. All known resistant cultivars possess a single dominant resistance gene, Tsw. Following TSWV infection, Tsw induces a hypersensitive-like reaction (HR), characterized by local necrotic lesions, that prevents the spread of the virus from the point of entry. Recently, naturally occurring resistance-breaking TSWV strains have been identified, causing major concern. We are utilising a collection of RB-TSWV strains to identify the specific genetic determinant that allows the virus to overcome the Tsw gene in Capsicum. As a reverse genetic approach is not feasible for minus-strand genome plant viruses such as TSWV, we set up a series of reassortment experiments between the wild-type strain Br01 and RB- TSWV strains. Our results confirm that the S RNA, which encodes both the nucleocapsid (N) and a nonstructural protein (NSs), carries the genetic determinant responsible for the breakdown of Tsw resistance. Sequence comparison between full-length S RNA segments of wild type and RB strains allows us to speculate about the specific genetic determinant of the “avirulence” factor.

Martinez-Ochoa N¹, Mullis SW¹, Csinos AS¹, Webster TM², Bertrand¹ P

¹Dept. of Plant Pathology, University of Georgia, Tifton GA 31793 U.S.A.

²CPMRU, USDA-ARS, Tifton GA 31793 U.S.A.

Correspondence: nmartinez8@alltel.net

Tomato spotted wilt virus (TSWV) is now endemic to the southeastern United States, where it affects major agricultural crops such as tomato, pepper, tobacco, peanut and numerous ornamentals as well. Due to milder winters and longer humid and warm summers in Georgia, there are favorable conditions for a succession of plant species that could serve as tospovirus reservoirs and more importantly, for a place for the thrips vectors to reproduce throughout the year. A three-year survey was conducted in nine Georgia tobacco fields to determine the weed species that were naturally infected with TSWV. Samples were taken on a monthly basis from most weed types at each location, and leaf and root tissues were tested together using DAS-ELISA (Agdia Inc.). In the winter and spring, Oenothera laciniata Hill (cutleaf evening primrose), Gnaphalium pensylvanicum Wild. (wandering cudweed), G. purpureum L. (purple cudweed), Eupatorium capillifolium (Lam.) Small (dogfennel), Lepidium virginicum L. (Virginia pepperweed), and Geranium carolinianum L. (Carolina geranium), were among the wild plant species most commonly infected with TSWV. In the summer and fall, the most common species found testing positive for TSWV were Jacquemontia tamnifolia (L.) Griseb. (smallflower morningglory), Richardia scabra L. (Florida pusley), Portulaca pilosa L. (broadleaf pink purslane), Desmodium tortuosum (Sw.) DC. (Florida beggarweed), Amaranthus retroflexus L. (redroot pigweed), and Wahlenbergia marginata (Thunb.) A. DC. (southern rockbell). There were a few plant species that did not test positive for TSWV during the entire survey period, and examples of those were Viola fafinesquii Greene (field pansy), Cardamine hirsuta L. (hairy bittercress), Diodia teres Walt (poorjoe), Veronica arvensis L. (corn speedwell), and Phylotacca americana L. (common pokeweed). Focus in follow-up surveys is being aimed at a select group of the most commonly TSWV-infected weeds found that are also reported as being reproductive hosts for the thrips vectors. In addition to weather and thrips vector populations, it is expected that seasonal incidences of TSWV in their weed reservoirs might be useful in predicting TSWV levels when planting susceptible field crops.

R Marullo

Dipartimento di Agrochimica ed Agrobiologia, Università degli Studi Mediterranea di Reggio Calabria, Italy.

Correspondence: rmarullo@unirc.it

Data on the host plant ranges for thrips species are often scanty, and are commonly derived from adult specimens that may have dispersed from their breeding sites. Because of this, there are many difficulties to present a comprehensive list of the host plants for most Thysanoptera species. Despite this, different thrips species exploit the available plants to varying extents, such that some may be considered as monophagous, oligophagous or even polyphagous. Polyphagous thrips species are more likely to be pest species than monophagous or oligophagous species (Moritz G et al. 2004. Pest thrips of the world: an identification and information system using molecular and microscopical methods). Also polyphagous species sometimes produce localized strains with a strong attachment to a particular plant species. Polyphagy and host range might be related to availability of particular compounds in the host plants (Terry I. 1997. In: Thrips as Crop Pests, 65–118), or such thrips species might be unusually flexible in their feeding behaviour. However, host plant associations sometimes vary between localities, and a few thrips species are known to exhibit remarkable host shifts (Mound LA. 2005. Annual Reviews of Entomology 50: 247–269), such that they become pests on plants unrelated to their “natural” hosts. In the present talk two species from southern Italy are considered that have remarkably disjunct host relationships: Neohydatothrips gracilicornis (Williams) on Vicia (Fabaceae) and Pinus (Pinaceae) (Marullo R. 1990. Redia 73 :223–228), and Drepanothrips reuteri Uzel on Vitis (Vitaceae) and Quercus (Fagaceae). In contrast the polyphagous species Heliothrips haemorrhoidalis (Bouchè) is expanding as a pest in forest areas, whereas it is no longer a severe pest of Citrus on which crop it is completely supplanted by Pezothrips kellyanus (Bagnall) in the intensive citrus southern orchards (Navel orange, lemon and bergamot). Here, for each thrips species, the main features of the life history, based on field data, and the “status” on the new host plants are focused and discussed. N.gracilicornis breeds on plants of wild Vicia spp., and also other Fabaceae, larvae develop mainly in the flowers of these host plants and pupate into the soil. The species is univoltine and overwinters as an adult living in litter or amongst plant debris in the soil. Adults can feed on Pinus needles during autumn and winter, but damage symptoms are induced only on weakly growing plants. Instead, both D.reuteri and H.haemorrhoidalis have Quercus as host plant, on which they breed and can have a few generations per year.

Matsuura S¹, Hoshino S¹, Koga H²

¹Hiroshima Prefectural Agriculture Research Center, Higashi-hiroshima, Hiroshima 739-0151, Japan.

²Taiyo Corporation Co. Ltd, Higashi-yodogawa, Osaka 533-0023, Japan

Correspondence: s-matsuura81314@pref.hiroshima.jp

The effect was investigated of verbena as a trap crop on the occurrence of western flower thrips, Frankliniella occidentalis, and the incidence of TSWV in chrysanthemums. Verbena cvs Pink Parfait and/or Fancy Parfait were cultivated alongside chrysanthemum cv. Jimba in a greenhouse at the proportion of 17–25% of chrysanthemum plants. Verbena cultivation suppressed the occurrence of western flower thrips on chrysanthemum until flower bud initiation by attracting vector thrips, and reduced TSWV incidence in the chrysanthemums up to flowering to 13–18% of untreated controls. We found that linalool oxide (pyran), an attractive volatile for vector thrips (Hooper et al. 1999: Pestic Sci 55:660–662), was mainly produced by the flower of verbena cv. Fancy Parfait and the ratio of cis and trans-type was 1 : 5. Our results suggest that cultivation of verbena as a trap crop suppresses TSWV incidence in the chrysanthemums up to the flowering stage and has the potential to be utilized as a control measure in IPM programs.

Medeiros RB¹, J Figueiredo J¹, RO Resende RO², Avila AC³

¹Dept. Fitopatologia and ²Biologia Celular, Universidade de Brasília, Brasília-DF, Brazil.

²Dept. Biologia Celular, Universidade de Brasília, Brasília-DF, Brazil

³Centro de Hortaliças, Empresa Brasileira de Pesquisa Agropecuária, Brasília-DF, Brazil.

Correspondence: demed002@umn.edu

Tospoviruses are the only plant-infecting members of the Bunyaviridae family of ambisense ssRNA viruses. Tomato spotted wilt tospovirus (TSWV), the type-member, also causes mild infection on its main insect vector, Frankliniella occidentalis. Herein, we identified an F. occidentalis putative transcription factor (FoTF) that binds to the TSWV RNA-dependent RNA polymerase and to viral RNA. Using in vitro RNA synthesis assays, we show that addition of purified FoTF improves viral replication, but not transcription. Expression of FoTF deletion mutants, unable to bind the RNA-dependent RNA polymerase or viral RNA, blocks TSWV replication in F. occidentalis cells. Finally, expression of FoTF wild-type turns human cell lines permissive to TSWV replication. These data indicate that FoTF is a host factor required for TSWV replication in vitro and in vivo, provide an experimental system that could be used to compare molecular defense mechanisms in plant, insect, and human cells against the same pathogen (TSWV), and could lead to a better understanding of evolutionary processes of ambisense RNA viruses. Financial Support: CNPq (CBAB), Embrapa, UnB, FINATEC.

Mikunthan G¹, Manjunatha M²

¹Dept. Agricultural Biology, Faculty of Agriculture, University of Jaffna, Jaffna, Sri Lanka.

²Department of Entomology, College of Agriculture, Shimoga 577201, Karnataka, India

Correspondence: gunamiku@sify.com

The Chili Thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae) is considered as a polyphagous insect pest causing severe upward leaf curl in chili (Capsicum annuum L.). This dreaded pest is being controlled by frequent use of selective and expensive systemic insecticides however, resistance developed in these insects limits the long term application and dependency on these chemicals in near future. Biological control is a viable alternative strategy that can be incorporated in to the integrated management of thrips to overcome this problem. However a sound knowledge of the natural enemy complex is very essential as an opted alternate choice to chemicals. Among the natural enemy complex, pathogens regulating the population of S. dorsalis have not been extensively studied. Added to this, there are no reports available on fungi infecting S. dorsalis. An attempt was made to isolate entomopathogenic fungi from chili fields and to evaluate their pathogenicity against S. dorsalis. A roving survey was conducted during 2002 to collect soil and foliage samples from chili fields representing ten agroclimatic zones of the Karnataka State of India. Entomopathogenic fungi were isolated from soil using a soil bait method (Zimmerman G. 1986. Journal of Applied Entomology 102: 213–215; Parker BL et al.1996. In: Tospoviruses and thrips, ISHS Acta Horticulturae 431: 521–534) and from infected cadavers collected from chili leaves. Larvae of Tribolium castaneum (Coleoptera: Tenebrionidae) and wax moth, Galleria melonella (Lepidoptera: Galleridae) were used as soil baits. Thirteen fungal isolates were recovered from soil using larvae of T. castaneum and G. melonella. However none of them were able to infect on any stages of S. dorsalis. Three fungi viz. Fusarium sp. isolate GM15 (ARSEF 7381), Neozygites floridana and Penicillium sp. were isolated from diseased cadavers of larvae of S. dorsalis and Fusarium semitectum (ARSEF 7233) from larvae of S. dorsalis, active stages of Polyphagotarsonemus latus (Acarina: Tarsonemidae) and nymphs and adults of Aphis gossypii (Hemiptera: Aphididae) from chili leaves. A local isolate of Metarhizium anisopliae was also found infective to adults of S. dorsalis and caused 13 per cent mortality. The isolation of entomopathogenic fungi from S. dorsalis and Fusarium species from S. dorsalis, P. latus and A. gossypii are new records. Koch’s postulates confirmed the infectivity of Fusarium isolates on S. dorsalis and the pathogenicity studies revealed that F. semitectum and Fusarium sp. isolate GM15 caused 86 and 76 per cent mortality of larvae of S. dorsalis, respectively. N. floridana caused 82 per cent mortality. These results show the potential use of entomopathogenic fungi in controlling S. dorsalis. The identity of the Fusarium isolates was confirmed by Dr. D. M. Geiser, Pennsylvania State University and Neozygites floridana by Dr.R.A.Humber of USDA-ARSEF, Collection of Entomopathogenic Fungal Cultures.

Minaei K¹, Alichi M²

¹Plant Protection Department, College of Agriculture, Tehran University, Karaj-Iran.

²Plant Protection Department, College of Agriculture, Shiraz University, Iran

Correspondence: kminaei@ut.ac.ir

During investigations on the thysanopteran fauna of Shiraz (Fars province, south west of Iran) and its vicinity in 1999–2002, forty-two species from 5 families and 23 genera were collected. They are listed according to their families as follows: Family Adiheterothripidae- Holarthrothrips josephi Bhatti; Family Aeolothripidae- Aeolothrips collaris Priesner, Aeolothrips intermedius Bagnall, Aeolothrips tenuicornis Bagnall, Aeolothrips versicolor Uzel, Orothrips priesneri (Titschack), Rhipidothrips gratiosus Uzel; Family Melanthripidae- Melanthrips fuscus Sulzer, Melanthrips rivnayi Priesner, Melanthrips separandus Priesner; Family Phlaeothripidae: Cephalothrips coxalis Bagnall, Compsothrips albosignatus (Reuter), Haplothrips aculeatus (Fabricius), Haplothrips flavitibiae Williams, Haplothrips niger (Osborn), Haplothrips reuteri Karny, Haplothrips subtilissimus (Haliday), Haplothrips tolerabilis Priesner, Haplothrips tritici Kurdjumov, Liothrips pragensis Uzel, Megathrips flavipes (Reuter), Pseudocryptothrips meridionalis Priesner; Family Thripidae- Agrostothrips meridionalis (Bagnall), Anaphothrips obscurus (Muller), Anaphothrips sudanensis Trybom, Chirothrips kurdistanus Zur Strassen, Chirothrips pallidicornis Priesner, Frankliniella intonsa (Trybom), Frankliniella pallida Uzel, Frankliniella tenuicornis (Uzel), Neohydatothrips tadzhicus (Pelikan), Odontothrips confusus Priesner, Retithrips syriacus (Mayet), Scirtothrips mangifera Priesner, Scolothrips latipenis Priesner, Sitothrips arabicus Priesner, Tenothrips discolor (Karny), Tenothrips frici (Uzel), Thrips major Uzel, Thrips meridionalis (Priesner), Thrips minutssimus Linnaeus, Thrips tabaci Lindeman. The species Aeolothrips versicolor, Haplothrips subtilissimus and Scolothrips latipenis are predators of small arthropods and spider mites respectively. Compsothrips albosignatus, Megathrips flavipes, and Pseudocryptothrips meridionalis feed on fungal spores. The other species are considered phytophages or pollen-feeders. (Minaei K. 2000. Thysanoptera fauna of Shiraz and vicinity. M. Sc. Thesis, Shiraz University, Shiraz, Iran; Minaei K et al. 2001. Iran Agircultural Rearch 20: 53–66)

Minaei K, Azemayeshfard P

Plant Protection Department, College of Agriculture, Tehran University, Karaj-Iran.

Correspondence: kminaei@ut.ac.ir

About 161 thrips species from 5 families and 60 genera have been recorded in Iran. However information related to the species composition of thrips populations and the significance of species as potential phytophages or carnivores has been given less attention, and much of the published data on host plant ranges of thrips is inaccurate in our country. At present, eight species are considered to damage cultivated plants in Iran: Anaphothrips obscurus (Müller), Drepanothrips reuteri Uzel, Haplothrips tritici (Kurdjumov), Pseudodendrothrips mori (Niwa), Retithrips syriacus (Mayet), Rubiothrips vitis (Priesner), Thrips flavus Schrank and T. tabaci Lindeman. Furthermore, there are some superficial reports on thrips pests. Thrips tabaci is the most damaging insect pest of onions in Iran. This species and wheat thrips (Haplothrips tritici) are the two that get most attention from Iranian entomologists due to their economic importance. The presence of the introduced thrips, Frankliniella occidentalis (Pergande) has been confirmed but there is no information on its pest status and distribution. Four known vector species of Tospoviruses are recorded in Iran: Frankliniella intonsa, F. occidentalis, F. schultzei, and Thrips tabaci.Tomato spotted wilt virus (TSWV) has been recorded in Iran, and transmission of cineraria (Senecio sp.) isolate of TSWV has been confirmed by Thrips tabaci. Recently a new Tospovirus species infecting tomato namely Tomato fruit yellow ring virus has been recorded in Iran. (Bhatii JS, et al.. 2003. Proc. Natnl. Symp. Frontier Areas Ent. Res., Pp. 668–669; Ghotbi T et al. 2005. Plant Disease 89: 425–429).

Moritz G

Martin-Luther-University Halle-Wittenberg, Developmental Biology, Domplatz 4, 06108 Halle, Germany.

Correspondence: gerald.moritz@zoologie.uni-halle.de

Tospoviruses are now recorded from more than 500 plant species in over 50 families. These viruses use only about 11 thrips vectors to move from one plant to another. The transmission of the virus by adult thrips is only successful if the first or early second larval stage acquires the virus during feeding on infected plant tissue. Wijkamp I et al. 1996 (Annals of Applied Biology 129: 303–313) determined a median acquisition access period (AAP₅₀) and pointed out that transmission ability increases with the length of the AAP on virus-infected material given to thrips larvae of Frankliniella occidentalis. On the other hand Sakurai T et al. 2002 (In: Marullo R, Mound LA, editors. Thrips and Tospoviruses: Proceedings of the 7^thInternational Symposium on Thysanoptera, 51–57. Canberra: Australian National Insect Collection) describe intraspecific variation in transmission of TSWV from several populations of western flower thrips in Japan and pointed out that males transmit TSWV with higher efficiencies than females. Developmental studies of ontogenetic stages of thrips including their inner morphology let these results appear in a completely new light (Moritz G et al. 2004. Virus Research 100: 143–149). The so called short germ band in thrips shows a top-down-segmentation with a successive segment specification ((Tautz D. 2004. Developmental Cell 7: 301–312)). Shortly after katatrepsis the lobed salivary gland material appears behind the brain. In the first larval stage, the small time frame for virus acquisition is determined when the epithel cells of the mid gut and the salivary gland cells come in tight contact because the brain is displaced out of the small larval head by large cibarial muscles. Variable acquisition rates are the result of movements of the brain and the growing mid gut in size and length. An effective virus transfer cell ensemble exists only for a few hours. The reposition of the brain and the formation of the oscillatory flight muscles end the possibility to acquire tospoviruses definitely

Moritz G¹, Mound LA², Kumm S¹

¹ Martin-Luther-University Halle-Wittenberg, Developmental Biology, Domplatz 4, 06108 Halle, Germany.

² CSIRO Entomology, P.O. Box 1700, Canberra, ACT 2601, Australia

Correspondence: gerald.moritz@zoologie.uni-halle.de

Situation: In the last decades the importance of pest thrips has increased considerably worldwide. These species are usually highly adaptable, with a well developed resistance against certain insecticides and with a tendency to be vectors of fungi, bacteria and viruses. Some of them are invasive, and are notorious for causing extensive crop damage (Morse CG, Hoddle MS. 2007. Annual Review of Entomology 51: 67–89). Their identification is important to understand their biology and to empower integrated pest management strategies. However, it is questionable how effectiv