Tomato Spotted Wilt Virus Transmission Research Articles

Dehydration and tomato spotted wilt virus infection combine to alter feeding and survival parameters for the western flower thrips, Frankliniella occidentalis

Dehydration and tomato spotted wilt virus (TSWV) infection substantially impact the feeding of western flower thrips, Frankliniella occidentalis. Until now, the dynamics between these biotic and abiotic stresses have not been examined for thrips. Here, we report water balance characteristics and changes in other biological parameters during infection with TSWV for the western flower thrips. There were no apparent differences in water balance parameters during TSWV infection of male or female thrips. Our results show that, although water balance characteristics of western flower thrips are minimally impacted by TSWV infection, the increase in feeding and activity when dehydration and TSWV are combined suggests that virus transmission could be increased under periods of drought. Importantly, survival and progeny generation were impaired during TSWV infection and dehydration bouts. The negative impact on survival and reproduction suggests that the interactions between TSWV infection and dehydration will likely reduce thrips populations. The opposite effects of dehydration on feeding/activity and survival/reproduction for virus infected thrips suggest the impact of vectorial capacity will likely be minor for TSWV transmission. As water stress significantly impacts insect-plant-virus dynamics, these studies highlight that all interactions and effects need to be measured to understand thrips-TSWV interactions in their role as viral vector to plants.

Comprehensive analysis of lysine lactylation in Frankliniella occidentalis.

Western flower thrips (Frankliniella occidentalis) are among the most important pests globally that transmit destructive plant viruses and infest multiple commercial crops. Lysine lactylation (Klac) is a recently discovered novel post-translational modification (PTM). We used liquid chromatography-mass spectrometry to identify the global lactylated proteome of F. occidentalis, and further enriched the identified lactylated proteins using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO). In the present study, we identified 1,458 Klac sites in 469 proteins from F. occidentalis. Bioinformatics analysis showed that Klac was widely distributed in F. occidentalis proteins, and these Klac modified proteins participated in multiple biological processes. GO and KEGG enrichment analysis revealed that Klac proteins were significantly enriched in multiple cellular compartments and metabolic pathways, such as the ribosome and carbon metabolism pathways. Two Klac proteins were found to be involved in the regulation of the TSWV (Tomato spotted wilt virus) transmission in F. occidentalis. This study provides a systematic report and a rich dataset of lactylation in F. occidentalis proteome for potential studies on the Klac protein of this notorious pest.

Different Methods for Detection and Diagnosis of Tomato Spotted Wilt Tospovirus Infection of some Cucurbit Host Plants and its Main Vector of Thrips Species in Field and Greenhouse in Egypt

The study recorded for the first time in Egypt the presence of tomato spotted wilt virus (TSWV) on cucurbits, which was confirmed using several serological tests, like double antibody sandwich ELISA (DAS-ELISA); Dot-blot ELISA assay and Immuno capture polymerase chain reaction (IC-PCR). By using Dot blot immunoassay test reaction against TSWV antisera, the ability of thrips species Thrips tabaci (Lind), Thrips palmi (Karny), and Frankliniella occidentalis (​Pergande), on the transmission of the (TSWV) were asserted. In the greenhouse, eleven plant species were determined as the host range of virus and field samples showed the similar symptoms. The mechanical transmission of TSWV showed a positive reaction bearing symptoms on the leaves of Cucumber, zucchini, smoke, datura and tomato plants 15-20 days after inoculation with transmission rates of 46.5, 40, 46.5, 46.5 and 86.5%, respectively. DAS-ELISA using antisera of TSWV showed that the greenhouse leaves samples were infected; otherwise, an amplification of IC-PCR products of 500 bp was detected by agarose electrophoresis of total RNA isolated from infected leaves.

Application of Multiplex RT-PCR for Simultaneous Identification of Tomato Spotted Wilt Virus and Thrips Species in an Individual Thrips on Chrysanthemum

We have developed a simultaneous diagnostic method that can identify both the species of thrips and tomato spotted wilt virus (TSWV) that are problematic in chrysanthemum plants. This is a method of amplifying DNA by performing reverse transcription-polymerase chain reaction by simultaneously adding primers specific to TSWV coat protein (N) gene and primers specific to the internal transcribed spacer 2 region of Frankliniella occidentalis and F. intonsa using total nucleic acid extracted from one thrips. The sizes of DNA fragments for TSWV, F. occidentalis, and F. intonsa were 777, 287, and 367 bp, respectively. These results showed species identification of thrips and whether thrips carrying TSWV can be simultaneously confirmed. Further usefulness of the simultaneous diagnostic method was made from greenhouse survey at chrysanthemum greenhouses in Taean (Chungcheongnam-do) and Changwon (Gyeongsangnam-do) to investigate the identification of thrips species and the rate of thrips carrying TSWV. Of thrips collected from the greenhouses, 83.7% thrips was F. occidentalis and 72.9% F. occidentalis carried TSWV in Taean. Similarly, the diagnostic method showed that 92.2% thrips was F. occidentalis and 84.0% F. occidentalis carried TSWV in Changwon. These results confirm that F. occidentalis is a dominant thrips species and the thrips species plays a crucial role in the transmission of TSWV in chrysanthemum plants in the greenhouses. Taken together, this study showed a simple diagnostic method for thrips identification and epidemiological studies of the timing and spread of TSWV through thrips in chrysanthemum greenhouses in South Korea.

Persistently Transmitted Viruses Restrict the Transmission of Other Viruses by Affecting Their Vectors.

Diverse pathogens, plant hosts, insect vectors, and non-vector herbivores coexist and interact in natural systems. An example is the cooccurrence of insects Bemisia tabaci Q and Frankliniella occidentalis and the pathogens tomato yellow leaf curl virus (TYLCV) and tomato spotted wilt virus (TSWV) on the same plant. In addition, both TYLCV and TSWV are persistently transmitted in these insect species. However, TSWV reduces the fitness of B. tabaci Q; therefore, we investigated whether TSWV affects the transmission of TYLCV to tomato. Both TYLCV and TSWV are persistently transmitted. Although B. tabaci Q cannot transmit TSWV, we found that this insect species is able to acquire and retain this virus serotype, indicating that the effects of TSWV on TYLCV transmission in the current study result from effects on the vector. The acquisition, retention, and transmission of TYLCV by B. tabaci Q were reduced when the insect vector contained TSWV. Additionally, the TYLCV acquisition and transmission by B. tabaci Q were reduced when the host plant was inoculated with TSWV before TYLCV or simultaneously with TYLCV. We also found that F. occidentalis fecundity and transmission of TSWV were reduced when F. occidentalis contained TYLCV. Our findings are consistent with the hypothesis that persistently transmitted viruses can restrict the transmission of other viruses by affecting their insect vectors.

Western Flower Thrips Can Transmit Tomato spotted wilt virus From Virus-infected Tomato Fruits

In this study, we demonstrate that western flower thrips (WFT, Frankliniella occidentalis) can acquire and transmit Tomato spotted wilt virus (TSWV) from symptomatic tomato fruits. TSWV and other thrips-transmitted tospoviruses have long been known to spread via plant propagation material such as transplants. Global dissemination of tospoviruses has also been linked, in part, to transport and trade of thrips-infested and virus-infected horticultural products. However, the role of tomato fruits transported across state and national borders has not previously been examined as a means of virus spread or as a source for thrips acquisition of virus. Tomato fruits displaying typical tospovirus symptoms were purchased from several Washington State grocery stores. Many of these symptomatic fruits tested positive for TSWV and some for Pepino mosaic virus (PepMV). First instar larvae of WFT successfully acquired TSWV from these infected tomato fruits and transmitted the virus as adults to Emilia sonchifolia plants. Symptomatic E. sonchifolia plants were confirmed positive for TSWV by lateral flow immunoassays and sequence analysis of a portion of the nucleocapsid gene. These results suggest the dissemination of TSWV (and likely other tospoviruses) and PepMV to new geographic areas by human-assisted transport of infected tomato fruits.

Thrips counts and disease incidence in response to reflective particle films and conservation tillage in cotton and peanut cropping systems.

Feeding damage to seedling cotton and peanut inflicted by adult and immature thrips may result in stunted growth and delayed maturity. Furthermore, adult thrips can transmit Tomato spotted wilt virus (TSWV) to seedling peanut, which reduces plant growth and yield. The objective of this research was to assess the efficacy of inert particle films, calcium carbonate or kaolin, in combination with conservation tillage, to reduce adult and immature thrips counts in cotton and peanut crops. Planting cotton or peanut into strip tillage utilizing a rolled rye winter cover crop significantly reduced immature thrips counts. Furthermore, plant damage ratings in cotton as well as TSWV incidence in peanut significantly decreased under conservation tillage. Aboveground cotton biomass and plant stand in cotton and peanut were unaffected by calcium carbonate or kaolin particle film applications. Within each week, immature thrips counts were unaffected by particle films, regardless of application rate. In cotton plots treated with kaolin, total Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) counts summed across weeks were significantly greater compared to the untreated control. For adult F. fusca counts at 3 weeks after planting, an interaction between tillage and particle film treatments was observed with fewer adult thrips in particle film and strip tillage treated peanut. Similarly, reduced TSWV incidence was observed in particle film‐treated peanut grown using conservation tillage. Neither cotton nor peanut yields were affected by particle film treatments.

Evaluation of Alternatives to Carbamate and Organophosphate Insecticides Against Thrips andTomato Spotted Wilt Virusin Peanut Production

Thrips are important pests of peanut. They cause severe feeding injuries on peanut foliage in the early season. They also transmit Tomato spotted wilt virus (TSWV), which causes spotted wilt disease. At-plant insecticides and cultivars that exhibit field resistance to TSWV are often used to manage thrips and spotted wilt disease. Historically, peanut growers used the broad-spectrum insecticides aldicarb (IRAC class 1A; Temik) and phorate (IRAC class 1B; Thimet) for managing thrips and thereby reducing TSWV transmission. Aldicarb has not been produced since 2011 and its usage in peanut will be legally phased out in 2018; therefore, identification of alternative chemistries is critical for thrips and spotted wilt management. Here, eight alternative insecticides, with known thrips activity, were evaluated in field trials conducted from 2011 through 2013. In addition, different application methods of alternatives were also evaluated. Imidacloprid (Admire Pro), thiamethoxam (Actara), spinetoram (Radiant), and cyantraniliprole (Exirel) were as effective as aldicarb and phorate in suppressing thrips, but none of the insecticides significantly suppressed spotted wilt incidence. Nevertheless, greenhouse assays demonstrated that the same alternative insecticides were effective in suppressing thrips feeding and reducing TSWV transmission. Spotted wilt incidence in the greenhouse was more severe (∼80%) than in the field (5–25%). In general, field resistance to TSWV in cultivars only marginally influenced spotted wilt incidence. Results suggest that effective management of thrips using alternative insecticides and subsequent feeding reduction could improve yields under low to moderate virus pressure.

Sex-Specific Influences of Frankliniella occidentalis (Western Flower Thrips) in the Transmission of Tomato Spotted Wilt Virus (Tospovirus)

The tospovirus-plant-vector interaction is a specific and complex relationship. It is established that several factors influence this interaction leading to high variability of transmission efficiency of the virus within a vector population. We studied the contribution of vector gender to this interaction using Frankliniella occidentalis (western flower thrips) reared on either Tomato spotted wilt virus (TSWV) infected or uninfected Capsicum annum leaflets throughout their larval stages. Later pupae were individually transferred onto healthy leaf disks to examine the differences in: survival, development rate, transmission efficiency and feeding behavior between males and females in all the treatments. This was based on the hypothesis that sex of the vector influences transmission efficiency within the vector population. Our results showed that males had significantly higher longevity, lower mortality and shorter development time compared to females, while in the comparison of feeding behaviour, females were found to feed more intensively than males, regardless of whether they were exposed or unexposed to TSWV. Conversely, transmission efficiency; which referred to successful inoculation and establishment of the virus in the host plant after a given period of inoculative feeding, was found to be significantly higher in males compared to females, despite females having the highest percentage of transmitting individuals. These findings account in part for the high variability in vector competence of F. occidentalis within a population, which further give insight into the biological factors that may influence the transmission of TSWV by F. occidentalis.

Effect of Spinosad Resistance on Transmission of Tomato Spotted Wilt Virus by the Western Flower Thrips (Thysanoptera: Thripidae).

Tomato spotted wilt virus (TSWV) is transmitted by Frankliniella occidentalis (Pergande) in a persistent-propagative manner. We previously observed significant results in terms of feeding behavior of spinosad-susceptible (Ivf03) and -resistant (Spin-R) strains of F. occidentalis using electrical penetration graph. TSWV transmission by the two strains was compared in the present study. The results showed that the titer of TSWV-N RNA (a part of S RNA of TSWV and encoding the nucleocapsid protein) in Ivf03 and Spin-R strains was not significantly different after a 48-h inoculation access period. The TSWV transmission rate did not significantly differ between the two strains and was 51.0% for Ivf03 and 44.4% for Spin-R. The virus transmission rate was significantly higher for males than females of both strains. The virus transmission rate for males and females of Ivf03 was 68.1 and 33.8%, respectively; however, in case of Spin-R, it was 60 and 28.8% for males and females, respectively. Additionally, number of probes and duration of probes were generally greater for viruliferous females of Ivf03 than for viruliferous females of Spin-R but the total number and duration of noningestion probes did not significantly differ between males of the two strains. The latter finding behavior may help explain the similar transmission rates for the susceptible and resistant strains.

Effects of Thrips Density, Mode of Inoculation, and Plant Age on Tomato Spotted Wilt Virus Transmission in Peanut Plants.

Spotted wilt caused by tomato spotted wilt virus (TSWV; family Bunyaviridae; genus Tospovirus) is a serious disease of peanut (Arachis hypogaea L.) in the southeastern United States. Peanut genotypes with field resistance to TSWV are effective in suppressing spotted wilt. All commercially available genotypes with field resistance to TSWV were developed through conventional breeding. As a part of the breeding process, peanut genotypes are regularly screened under field situations. Despite numerous advantages associated with field screening, it is often limited by inconsistent vector (thrips) and TSWV pressure. A greenhouse transmission protocol would aid in thorough screening of selected genotypes and conserve time. In this study, various parameters associated with TSWV transmission, including tobacco thrips, Frankliniella fusca (Hinds) density, mode of inoculation, and plant age, were evaluated. Greater incidences of TSWV infection were obtained with thrips-mediated inoculation when compared with mechanical inoculation. TSWV inoculation with three, five, and 10 thrips resulted in greater incidences of TSWV infection in plants than inoculation with one thrips. However, incidences of TSWV infection did not vary between plants inoculated with three, five, and 10 viruliferous thrips. With both thrips-mediated and mechanical inoculation methods, incidences of TSWV infection in 1-wk-old plants were greater than in 4-wk-old plants. TSWV copy numbers, as determined by qPCR, also decreased with plant age. Results suggest that using at least three thrips per plant and 1- to 2-wk-old plants would maximize TSWV infection in inoculated plants.

Disruption of Vector Transmission by a Plant-Expressed Viral Glycoprotein

Vector-borne viruses are a threat to human, animal, and plant health worldwide, requiring the development of novel strategies for their control. Tomato spotted wilt virus (TSWV) is one of the 10 most economically significant plant viruses and, together with other tospoviruses, is a threat to global food security. TSWV is transmitted by thrips, including the western flower thrips, Frankliniella occidentalis. Previously, we demonstrated that the TSWV glycoprotein GN binds to thrips vector midguts. We report here the development of transgenic plants that interfere with TSWV acquisition and transmission by the insect vector. Tomato plants expressing GN-S protein supported virus accumulation and symptom expression comparable with nontransgenic plants. However, virus titers in larval insects exposed to the infected transgenic plants were three-log lower than insects exposed to infected nontransgenic control plants. The negative effect of the GN-S transgenics on insect virus titers persisted to adulthood, as shown by four-log lower virus titers in adults and an average reduction of 87% in transmission efficiencies. These results demonstrate that an initial reduction in virus infection of the insect can result in a significant decrease in virus titer and transmission over the lifespan of the vector, supportive of a dose-dependent relationship in the virus-vector interaction. These findings demonstrate that plant expression of a viral protein can be an effective way to block virus transmission by insect vectors.

Effect of cyantraniliprole on feeding behavior and virus transmission of Frankliniella fusca and Frankliniella occidentalis (Thysanoptera: Thripidae) on Capsicum annuum

The anthranilic diamide insecticide cyantraniliprole was previously shown to reduce transmission of Tomato spotted wilt virus (TSWV) to pepper, Capsicum annuum, by Frankliniella fusca but not Frankliniella occidentalis. This study examines the effects of cyantraniliprole and imidacloprid on thrips feeding using electrical penetration graphing (EPG), and on TSWV transmission in field cage studies. Some antifeedant responses were observed in the EPG studies when thrips fed on cyantraniliprole- and imidacloprid-treated plants; however, these responses were variable between species and among the 2, 6, and 10 day post-treatment time intervals during which feeding behavior was observed. Cyantraniliprole significantly reduced the probability of TSWV infection when spread by F. fusca in field-grown pepper when viruliferous thrips were released 7 days but not when released at 14 days after the insecticide treatment in one of 2 field trials. In the second trial cyantraniliprole significantly reduced the probability of infection when F. fusca were released 14 days but not 7 days after treatment. In both years, imidacloprid prevented or significantly reduced transmission of TSWV by F. fusca in field-grown pepper when viruliferous thrips were released 7 days and 14 after treatment. In one of two years, cyantraniliprole significantly reduced the incidence of TSWV in field-grown pepper that was spread by F. occidentalis when viruliferous thrips were released 7 days after the insecticide treatment, but not 14 days after the treatment. Imidacloprid did not reduce the incidence of TSWV in field-grown pepper when viruliferous F. occidentalis were released. Although these studies demonstrate that probing behavior of these thrips species is altered on cyantraniliprole-treated pepper plants, results of field cage studies did not consistently show a reduction in incidence of TSWV-infected plants.

Thrips tabaci population genetic structure and polyploidy in relation to competency as a vector of tomato spotted wilt virus.

Knowledge of population-level genetic differences can help explain variation among populations of insect vectors in their role in the epidemiology of specific viruses. Variation in competency to transmit Tomato spotted wilt virus (TSWV) that exists among populations of Thrips tabaci has been associated with the presence of cryptic species that exhibit different modes of reproduction and host ranges. However, recent findings suggest that vector competency of T. tabaci at any given location depends on the thrips and virus populations that are present. This study characterizes the population genetic structure of T. tabaci collected from four locations in North Carolina and examines the relationship between population genetic structure and variation in TSWV transmission by T. tabaci. Mitochondrial COI sequence analysis revealed the presence of two genetically distinct groups with one characterized by thelytokous, parthenogenetic reproduction and the other by arrhenotokous, sexual reproduction. Using a set of 11 microsatellite markers that we developed to investigate T. tabaci population genetic structure, we identified 17 clonal groups and found significant genetic structuring among the four NC populations that corresponded to the geographic locations where the populations were collected. Application of microsatellite markers also led to the discovery of polyploidy in this species. All four populations contained tetraploid individuals, and three contained both diploid and tetraploid individuals. Analysis of variation in transmission ofTSWV among isofemale lines initiated with individuals used in this study revealed that ‘clone assignment,’ ‘virus isolate’ and their interaction significantly influenced vector competency. These results highlight the importance of interactions between specific T. tabaci clonal types and specific TSWV isolates underlying transmission of TSWV by T. tabaci.

Specific insect-virus interactions are responsible for variation in competency of different Thrips tabaci isolines to transmit different Tomato Spotted Wilt Virus isolates.

Local adaptation between sympatric host and parasite populations driven by vector genetics appears to be a factor that influences dynamics of disease epidemics and evolution of insect-vectored viruses. Although T. tabaci is the primary vector of Tomato spotted wilt virus (TSWV) in some areas of the world, it is not an important vector of this economically important plant virus in many areas where it occurs. Previous studies suggest that genetic variation of thrips populations, virus isolates, or both are important factors underlying the localized importance of this species as a vector of TSWV. This study was undertaken to quantify variation in transmissibility of TSWV isolates by T. tabaci, in the ability of T. tabaci to transmit isolates of TSWV, and to examine the possibility that genetic interactions and local adaptation contribute to the localized nature of this species as a vector of TSWV. Isofemale lines of Thrips tabaci from multiple locations were tested for their ability to transmit multiple TSWV isolates collected at the same and different locations as the thrips. Results revealed that the probability of an isofemale line transmitting TSWV varied among virus isolates, and the probability of an isolate being transmitted varied among isofemale lines. These results indicate that the interaction of T. tabaci and TSWV isolate genetic determinants underlie successful transmission of TSWV by T. tabaci. Further analysis revealed sympatric vector-virus pairing resulted in higher transmission than allopatric pairing, which suggests that local adaptation is occurring between T. tabaci and TSWV isolates.

Serial Transmission of Plant Viruses by Cutting Implements during Grafting

Reciprocal grafts of two tomato (Solanum lycopersicum L.) cultivars were made by hand using commercial grafting techniques. The razor blade used to cut the rootstock or scion was first contaminated by making a single cut on tomato plants infected with either Tomato spotted wilt virus (TSWV) or Tomato mosaic virus (ToMV). Although no transmission of TSWV was observed in these experiments, ToMV was spread plant to plant through razor blade exposure to this virus. The presence of this virus was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) at 21 days post-inoculation. The highest rate of infection was 25% of the inoculated plants. The greatest number of positive virus assays was found in the first 10 plants of each experiment. These areas contained 84% of the DAS-ELISA-positive plants. Gaps of up to 10 plants occurred during serial inoculation before infection resumed. Random dispersion occurred in two experiments. Similar results were observed whether the contaminated implement was used to cut the rootstock or the scion before graft assembly. This work demonstrates that some viruses from a single contamination can be moved in a serial manner during the grafting process, especially with varieties with minimal or no resistance to viral plant pathogens. Also, visual diagnosis cannot always be relied on as a means of eliminating virus-infected plants, especially when higher greenhouse and annealing temperatures are maintained.

Direct and indirect effects of a thrips‐transmitted Tospovirus on the preference and fitness of its vector, Frankliniella fusca

AbstractPhytoviruses including tospoviruses are known to affect the behavior and fitness of their vectors both positively and negatively. In this study, we investigated the effects of Tomato spotted wilt virus (TSWV) (family Bunyaviridae, genus Tospovirus) infection on the fitness and feeding ability of tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) using peanut, Arachis hypogaea L. (Fabaceae), as a host. Potentially viruliferous F. fusca laid more eggs than non‐viruliferous F. fusca. In contrast, fewer potentially viruliferous F. fusca developed into adults and required a longer developmental time than non‐viruliferous F. fusca, indicating a direct negative effect of the virus on thrips fitness. In addition, no‐choice feeding tests indicated that non‐viruliferous F. fusca fed more rapidly than potentially viruliferous F. fusca. Typically, phytovirus infections are known to enhance the availability of vital nutrients such as free amino acids in infected host plants and to affect other important physiological processes negatively. Free amino acids are known to play a vital role in egg production and development. Further investigations in this study revealed that leaflets of infected plants had ca. 15 times more free amino acids than non‐infected leaflets. TSWV‐infected leaflets were used to rear potentially viruliferous thrips. Higher amino acid levels in TSWV‐infected leaflets than in non‐infected leaflets could have contributed to increased oviposition by potentially viruliferous F. fusca compared to non‐viruliferous F. fusca. Taken together, these results suggest that increased concentrations of free amino acids in TSWV‐infected plants might serve as an incentive for thrips feeding on otherwise unsuitable hosts, thereby facilitating TSWV acquisition and transmission.

Preliminary evidence of recovery from Tomato spotted wilt virus infection in Frankliniella occidentalis individuals

AbstractIn this study we analysed the ability of individual thrips to transmit Tomato spotted wilt virus (TSWV) in a population of Frankliniella occidentalis over their lifespan as adults (about 10 days). In three experiments a total of 636 thrips were individually tested for their transmission capacity through leaf disc assays using four inoculation access periods (IAPs). Almost half of the transmitting thrips maintained the capacity to infect leaf discs in each of the four IAPs, confirming the persistent propagative nature of the transmission modality. Nevertheless, a relevant number of thrips (9.25% of transmitter thrips) was able to transmit in the early phases of their adult life (for the first two IAPs), but did not transmit the virus for the remainder of their lifetime. We compared the virus titer of these individuals at the end of the fourth IAP with that of individuals that maintained transmission ability in the four IAPs and showed a statistically significant difference. This difference could be evidence for recovery from TSWV infection in individual thrips.

The effect of three rates of cyantraniliprole on the transmission of tomato spotted wilt virus by Frankliniella occidentalis and Frankliniella fusca (Thysanoptera: Thripidae) to Capsicum annuum

Abstract Tomato spotted wilt virus (TSWV) is a thrips-transmitted virus that causes major losses in many crops worldwide. Management of TSWV is complex, requiring multiple preventive measures. Currently, there are few chemical options that control thrips populations before they feed upon and transmit TSWV to crop plants. Cyantraniliprole (Cyazypyr™) is an anthranilic diamide insecticide currently under development that exhibits anti-feedant properties. Transmission of TSWV by Frankliniella fusca (Hinds) to Capsicum annuum L. seedlings was reduced in plants treated with Cyazypyr™ applied to the soil at the rates of 1.45, 2.90 and 4.41 mg ai/plant. Mortality of F. fusca at 3 days post treatment did not differ significantly on excised foliage of Cyazypyr™ treated and control plants, but feeding injury was significantly less on treated foliage. Transmission of TSWV by Frankliniella occidentalis (Pergande) was not reduced in plants treated with 4.41 mg ai/plant.

The impact of a parasitic nematode, Thripinema fuscum, on the feeding behavior and vector competence of Frankliniella fusca

Abstract Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) is the predominant thrips species found inhabiting and reproducing in peanut, Arachis hypogaea L. (Fabaceae), and is one of at least seven thrips species reported to transmit Tomato spotted wilt virus (TSWV). The entomogenous nematode Thripinema fuscum Tipping & Nguyen (Tylenchida: Allantonematidae), a natural enemy of F. fusca, parasitizes larval and adult populations under field conditions. All known Thripinema species render the host female thrips sterile and have the potential to suppress pest populations to near extinction. As a result, secondary spread of TSWV in peanut is reduced. Reduction of the virus under field conditions may also be due to lower transmission rates caused by parasite‐induced alterations in host feeding behavior. Therefore, the feeding rates of healthy and parasitized F. fusca male and female cohorts on leaf discs were recorded daily for 10 days and digital images were subjected to image analysis and viral transmission rates were compared daily using double antibody sandwich enzyme‐linked immunosorbent assay. Thripinema fuscum reduced the feeding of female F. fusca by nearly 65%, and the ability of females to transmit TSWV by 50%. Potential mechanisms underlying the parasite‐induced alterations in feeding behavior and transmission are discussed. Parasitism by T. fuscum significantly reduced male longevity, but female longevity was not affected. These results provide further evidence that T. fuscum aids in regulating viruliferous F. fusca pest populations and suggests its potential as a biological control agent for inoculative release in peanut.