Iris Yellow Spot Virus Research Articles

First report of iris yellow spot virus infecting shallot (Allium cepa var. aggregatum) in Australia

AbstractIn 2019, symptoms typical of infection by iris yellow spot virus (IYSV; family Tospoviridae, genus Orthotospovirus) were observed on shallot (A. cepa var. aggregatum) grown at the Gatton Research Facility, Department of Agriculture and Fisheries, Queensland. Initial testing by DAS-ELISA was positive for IYSV, and subsequent specific RT-PCR amplifying part of the RdRp (L-segment) and sequencing of amplicons confirmed the IYSV infection. This is the first record of IYSV infection of shallot in Australia.

Localization of Iris Yellow Spot Virus in Naturally Infected Onion Plants: A Sampling Approach for Reliable Diagnosis

Iris yellow spot virus (IYSV) from the genus Orthotospovirus of the family Tospoviridae can cause considerable yield reduction and crop loss in allium crops, especially dry bulb onion. While infected plants may or may not express symptoms of iris yellow spot disease, these onion plants can test negative for the virus because not all tissues contain detectable levels of IYSV due to its uneven distribution. The purpose of this study was to identify tissue locations of symptomatic onion plants that have the highest likelihood of testing positive for IYSV in DAS-ELISA using specific antibodies. Results revealed that the greatest likelihood of detecting IYSV from a single symptomatic plant occurred with tissue near foliar lesions located on the distal portions of older leaves (range: 42-71%). These low to moderate probability detection levels can predictably be overcome by testing pooled tissue samples from the same plant or from multiple plants. Indeed, the likelihood of distal and proximal youngest leaf tissue testing positive for IYSV from a single plant to a four-plant composite sample would increase from 44% to 90% and from 50% to 94%, respectively. Implications of these results for IYSV detection and surveillance in onion production systems are discussed.

Orthotospovirus iridimaculaflavi (iris yellow spot virus): An emerging threat to onion cultivation and its transmission by Thrips tabaci in India

The yellow spot disease caused by the virus species Orthotospovirus iridimaculaflavi (Iris yellow spot virus-IYSV), belonging to the genus Orthotospovirus, the family Tospoviridae, order Bunyavirales and transmitted by Thrips tabaci Lindeman. At present, emerging as a major threat in onion (Allium cepa) in Tamil Nadu, India. The yellow spot disease incidence was found to be 53–73 % in six districts out of eight major onion-growing districts surveyed in Tamil Nadu during 2021–2023. Among the onion cultivars surveyed, the cultivar CO 5 was the most susceptible to IYSV. The population of thrips was nearly 5–9/plant during vegetative and flowering stages. The thrips infestation was 34–60 %. The tospovirus involved was confirmed as IYSV through DAS-ELISA, followed by molecular confirmation through RT-PCR using the nucleocapsid (N) gene. The predominant thrips species present in onion crops throughout the growing seasons was confirmed as Thrips tabaci based on the nucleotide sequence of the MtCOI gene. The mechanical inoculation of IYSV in different hosts viz., Vigna unguiculata, Gomphrena globosa, Chenopodium amaranticolor, Chenopodium quinoa and Nicotiana benthamiana resulted in chlorotic and necrotic lesion symptoms. The electron microscopic studies with partially purified sap from onion lesions revealed the presence of spherical to pleomorphic particles measuring 100–230 nm diameter. The transmission of IYSV was successful with viruliferous adult Thrips tabaci in cowpea (Cv. CO7), which matured from 1st instar larva fed on infected cowpea leaves (24 h AAP). Small brown necrotic symptoms were produced on inoculated plants after an interval of four weeks. The settling preference of non-viruliferous and viruliferous T. tabaci towards healthy and infected onion leaves resulted in the increased preference of non-viruliferous thrips towards infected (onion-61.33 % and viruliferous thrips towards healthy onion leaves (75.33 %). The study isolates shared 99–100 % identity at a nucleotide and amino acid level with Indian isolates of IYSV in the N gene. The multiple alignment of the amino acid sequence of the N gene of IYSV isolates collected from different locations and IYSV isolates from the database revealed amino acid substitution in the isolate ITPR4. All the IYSV isolates from India exhibited characteristic amino acid substitution of serine at the 6th position in the place of threonine in the isolates from Australia, Japan and USA. The phylogenetic analysis revealed the monophyletic origin of the IYSV isolates in India.

Molecular identification and characterization of iris yellow spot virus (IYSV) and garlic virus X (GVX) infecting Allium species

Molecular identification and characterization of iris yellow spot virus (IYSV) and garlic virus X (GVX) infecting Allium species

Iris yellow spot orthotospovirus pathosystem, virus host and vector (Thrips tabaci)

Iris yellow spot orthotospovirus (IYSV) causes serious problems in the onion (Allium cepa) crop and is widely distributed in the producing areas of the country. In Mexico it was reported in 2010 as “yellow spot” on onion and other members of the genus Allium. Its main vector is Thrips tabaci, which causes direct damage by feeding and by being a vector of other viruses such as Tomato spotted wilt orthotospovirus and Impatiens necrotic spot orthotospovirus. Knowledge of the pathosystem of IYSV - Thrips tabaci - Allium cepa - weeds can contribute to an integrated management and awareness of pesticide use. The versatility of IYSV to infect more than 60 plant species (>20 families), most of which are present in Mexico, coupled with the wide host range of the vector, makes the interaction complex and leads to a better understanding of the diversity of alternate hosts of the vector and/or IYSV. At present, information on weed hosts of IYSV and the vector is limited, but their knowledge will provide a greater understanding of the disease. It is important to have a comprehensive knowledge of the virus, main host, alternate hosts, and vector in the country, in order to channel future research to counteract this problem and minimize losses caused by IYSV in the onion crop mainly.

Advanced methods for insect nets: red-colored nets contribute to sustainable agriculture

Development of advanced pest control methods that do not rely on insecticides is an important issue for sustainable agriculture. Particularly with regards to micro pests that are not only highly resistant to various insecticides but also because we are running out of options for which insecticide to use against them, resulting in enormous economic damage worldwide. Here we report that the effectiveness of the conventional insect net can be greatly advanced by changing their color to red that helps significantly reduce pesticide use. We demonstrate the red effect using Onion thrips, Thrips tabaci a main vector of Iris Yellow Spot Virus (IYSV) and Tomato Spotted Wilt Virus (TSWV) that cause serious damage to various vegetables. New red nets succeeded in suppressing the invasion rates and damages (white spots on the leaves) in a Welsh onion greenhouse with minimum use of pesticides. We discuss how red nets are compatible with labor-saving, sustainable agriculture and the future potential of “optical pest control” based on insect color vision and its behavioral response.

Spatiotemporal Patterns of Iris Yellow Spot Virus and Its Onion Thrips Vector, Thrips tabaci, in Transplanted and Seeded Onion Fields in New York.

Onion thrips, Thrips tabaci (Lindeman), transmits iris yellow spot virus (IYSV) and is one of the most important pests of Allium crops. IYSV is a member of the species Tospovirus iridimaculaflavi in the genus Orthotospovirus of the family Tospoviridae. This virus typically reduces overall onion bulb quality and weight but can also prematurely kill onion plants. IYSV is neither seed nor mechanically transmitted. Onion fields are typically established via seeds and transplants. A decade ago, onion thrips tended to colonize transplanted fields before seeded fields because plants in transplanted fields were larger and more attractive to thrips than smaller onions in seeded fields. Therefore, we hypothesized that the incidence of IYSV in transplanted fields would be detected early in the season and be spatially aggregated, whereas IYSV would be absent from seeded fields early in the season and initial epidemic patterns would be spatially random. In 2021 and 2022, IYSV incidence and onion thrips populations were quantified in 12 onion fields (four transplanted fields and eight seeded fields) in New York. Fields were scouted four times throughout the growing season (n = 96 samples), and a geospatial and temporal analysis of aggregation and incidence was conducted to determine spatiotemporal patterns in each field type. Results indicated that spatial patterns of IYSV incidence and onion thrips populations were similar early in the season, indicating that transplanted onion fields are no longer the dominant early-season source of IYSV in New York. These findings suggest the need to identify other important early-season sources of IYSV that impact New York onion fields.

Identifying Onion Fields at Risk of Iris Yellow Spot Virus in New York.

Iris yellow spot virus (IYSV) poses a significant threat to dry bulb onion, Allium cepa L., production and can lead to substantial yield reductions. IYSV is transmitted by onion thrips, Thrips tabaci (Lindeman), but not via seed. Transplanted onion fields have been major early season sources of IYSV epidemics. As onion thrips tend to disperse short distances, seeded onion fields bordering transplanted onion fields may be at greater risk of IYSV infection than seeded fields isolated from transplanted ones. Additionally, seeded onion fields planted early may be at greater risk of IYSV infection than those seeded later. In a 2-year study in New York, we compared IYSV incidence and onion thrips populations in seeded onion fields relative to their proximity to transplanted onion fields. In a second study, we compared IYSV incidence in onion fields with either small or large plants during midseason. Results showed similar IYSV incidence and onion thrips populations in seeded onion fields regardless of their proximity to transplanted onion fields, while IYSV incidence was over four times greater in large onion plants than in small ones during midseason. These findings suggest a greater risk of onion thrips-mediated IYSV infection in onion fields with large plants compared with small ones during midseason and that proximity of seeded fields to transplanted ones is a poor indicator of IYSV risk. Our findings on IYSV spread dynamics provided valuable insights for developing integrated pest and disease management strategies for New York onion growers.

Weed Plants of the Asteraceae and Malvaceae Families as Reservoirs of Harmful Viruses of Vegetable Crops in Ukraine and the World

The review provides an analysis of the current literature data on the prevalence of weeds of the Asteraceae and Malvaceae families, which act as reservoirs of agricultural plant viruses, in the agroecosystems of both Ukraine and the world. The main focus is on weeds that are common in the agrocenoses of agricultural crops. The primary sources of the main pathogens of viral diseases of vegetable crops (Tomato spotted wilt virus (TSWV), Tomato chlorosis virus (ToCV), Tomato yellow leaf curl virus (TYLCV), Cucumber mosaic virus (CMV), Cucumber vein yellowing virus (CVYV), Iris yellow spot virus (IYSV), and Pepino mosaic virus (PepMV)) in different climatic zones, as well as the main factors contributing to the spread of harmful viruses in agrophytocenoses are analyzed.

Onions Selected for Reduced Symptom Expression of Iris Yellow Spot Have Higher Photosynthetic Rates

Bulb onion (Allium cepa L.) is an economically valuable vegetable crop in the United States. Onion production is threatened by onion thrips, which are the vector for Iris yellow spot virus, which is the causal agent of Iris yellow spot (IYS). New Mexico State University (NMSU) breeding lines 12-236, 12-238, 12-243, and 12-337 have exhibited fewer IYS disease symptoms in the field; however, little is known about the effects of the disease on the photosynthesis rate (Pn). We hypothesized that these NMSU breeding lines would have a higher Pn than IYS-susceptible cultivars Rumba and Stockton Early Yellow. To test this hypothesis, a field study was conducted for 3 years at NMSU, and Pn was measured five times throughout each season at 2-week intervals. During bulb development and maturation, which occurred at 10 and 12 weeks after transplanting, all NMSU breeding lines exhibited a higher Pn when compared with that of an IYS-susceptible cultivar. Pn was highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all cultivars. Additionally, a high Pn at 10 and 12 weeks after transplanting coincided with high bulb weight at harvest. NMSU breeding lines have increased Pn compared with that of IYS-susceptible cultivars and resulted in larger and more marketable bulbs. These results indicate that maintaining Pn may be related to reduced IYS symptom expression of onion.

Performance of Onion Cultivars in the Treasure Valley of Eastern Oregon and Southwestern Idaho in 2010–20

Each year ≈24,000 acres of onions (Allium cepa) are produced in the Treasure Valley of eastern Oregon and southwestern Idaho, which accounts for 20% of U.S. dry-bulb onion acreage. Onions in this region are long-day onions and are irrigated by either furrow irrigation or drip irrigation, with drip irrigation having become the predominant system in the past 10 years. Onion production in the Treasure Valley faces many biotic pressures and changing market conditions that renders cultivar development and testing of critical importance to the onion industry. Direct-seeded yellow, white, and red onion cultivars have been evaluated yearly at the Malheur Experiment Station, Oregon State University, in Ontario, OR, USA, since 1975. From 2010 to 2020, 10 onion seed companies participated in the trials. There were 21 to 32 yellow cultivars, two to 10 red cultivars, and one to seven white cultivars entered in the trial each year. Only five cultivars were entered all 11 years. Total yields for the yellow cultivars ranged from an average of 680 cwt/acre in 2010 to 1277 cwt/acre in 2018, and averaged 961 cwt/acre over the 11 years. Yield of yellow bulbs larger than 4 inches (colossal and super colossal) ranged from 13% in 2010 to 61% in 2018, and averaged 34% over the 11 years. Single centered yellow bulbs ranged from 46% in 2013 to 70% in 2014. Total yields for the red cultivars averaged 520 cwt/acre and total yield of white cultivars averaged 988 cwt/acre over the 11 years. Over the 11 years, single-centered bulbs of red cultivars averaged 65% and single-centered bulbs of white cultivars averaged 45%. Some newer cultivars show improvements in single centeredness, resistance to Iris yellow spot virus, and yield of larger bulbs over cultivar Vaquero, which was released in 1993, indicating the success of breeding efforts. Yields of five yellow cultivars that were in the trials every year since 2010, increased over time. This increase can be partly attributed to improvements in cultural practices over the years: adoption of drip irrigation, more intensive nutrient management, refined onion thrips (Thrips tabaci) control, and higher plant population.

English

Onion thrips, Thrips tabaci Lindeman is a cosmopolitan and polyphagous insect pest. Onion thrips cause direct and indirect damage to onion by feeding and ovipositing on leaves of several horticultural crops. Besides causing direct damage to its host plants, T. tabaci has been known as an asymptomatic transmitter of plant pathogens such as tomato spotted wilt virus (TSWV), iris yellow spot virus (IYSV) and tomato yellow ring virus (TYRV). These cause reduction of yield and decrease the market value of the crop. Several synthetic insecticides are used to control the population of onion thrips. However, these insecticides cause pesticide resistance, elimination of non-target species and environmental pollution. To solve the side effects of insecticides, it should be replaced by environmentally friendly pest management alternatives and for this, the use of plant-based pesticides is the best alternative because they do not have residue problems, negative effects on beneficial insects and do not cause air and water quality problems in the environment. Several plants have been investigated which contain bioactive compounds with a variety of biological modes of actions against onion thrips such as repellent, feeding deterrent, anti-ovipositional, fecundity deterrent and metamorphosis inhibition. Key words: Botanical plants, integrated pest management (IPM), onion thrips, secondary metabolites, modes of action.

Stability and Hopf bifurcation analysis of a delayed eco-epidemiological model of IYSV disease dynamics in onion plants with nonlinear saturated incidence and logistic growth

Iris Yellow Spot Disease (IYSD), caused by Iris Yellow Spot Virus (IYSV) is a destructive and fastspreading virus disease of onion plants worldwide. It is mainly transmitted by an insect vector called thrips tabaci in a persistent and propagative manner and as such, there is a significant latent time after acquisition of the virus by the vector and an incubation time is needed for the appearance of disease symptoms on plants. In this paper, we formulate and analyze a non-linear mathematical model to explore the dynamics of IYSV disease in onion plants using system of delay differential equations by incorporating incubation and latent periods as time delays factors. The delays are introduced by adding an exposed population for onion plants representing the plants that are infected but not yet infective and by taking into account that there is fraction of the newly exposed onion plants that do not die during incubation period before becoming infective. It is assumed that the onion plant grows logistically in the farm so that the total onion plant population is taken as variable. The local stability of the disease-free equilibrium in the presence of delays is investigated using Descartes’s rule of signs. We establish the sufficient conditions for the stability of the endemic equilibrium in presence of delays and we investigate the occurrence of Hopf bifurcation when certain conditions are satisfied by considering the two delays as bifurcation parameters. We compute the critical values of the delays which preserve the local asymptotic stability of the endemic equilibrium and the model shows an oscillatory behavior beyond these critical values. Finally, numerical simulations are performed and displayed graphically to support the analytical results, and the eco-epidemiological implications of the key outcomes are briefly discussed.

Complejos virales en la interacción Allium cepa L.- Frankliniella occidentalis P., por DAS-ELISA en Baja California, México

The onion (Allium cepa L.) is one of the main horticultural crops produced in Baja California, Mexico. In this crop, it has been observed presumptive viral symptoms, which are able to cause losses in yield and quality. Therefore, the objective of this study was to detect the associated virus in onion in high producing culture zones in Baja California. Plant material samples (symptomatic and asymptomatic) and trips insects were collected from commercial farming or areas. Commercial anti-serum were used for the detection of Iris yellow spot virus (IYSV), Tomato spot wilt virus (TSWV), Leek yellow spot virus (LYSV), Onion yellow dwarf virus (OYDV) and Garlic common latent virus (GarCLV). Seven indicator plants species were mechanically inoculated with onion sap (symptomatic and asymptomatic). The results showed the presence of IYSV, TSWV, OYDV and GarCLV in symptomatic onion plants. The plant samples showed a 77 % of incidence in the form of viral complexes and in a 23 % only the presence of LYSV was detected. The trips identified as Frankiniella occidentalis P. harbored IYSV, TSWV, LYSV, OYDV and GarCLV in the form of complexes in La Trinidad and San Quintin. The indicator plants did not show sympotoms of virosis. It is evident that F. occidentalis P. is responsible for the transmision of the analyzed viruses in this study in cultured onions. There are not previous reports for the detection of Orthotospovirus, Potyvirus and Carlavirus in Baja California onions.

Complexity and Local Specificity of the Virome Associated with Tospovirus-Transmitting Thrips Species.

SUMMARYFrankliniella occidentalis (western flower thrips [WFT]) and Thrips tabaci (onion thrips [OT]) are insect species that greatly impact horticultural crops through direct damage and their efficient vectoring of tomato spotted wilt virus and iris yellow spot virus. In this study, we collected thrips of these species from 12 field populations in various regions in Italy. We also included one field population of Neohydatothrips variabilis (soybean thrips [ST]) from the United States. Total RNA data from high-throughput sequencing (HTS) were used to assemble the virome, and then we assigned putative viral contigs to each thrips sample by real-time reverse transcription-quantitative PCR (qRT-PCR). Excluding plant and fungal viruses, we were able to identify 61 viral segments, corresponding to 41 viruses: 14 were assigned to WFT, 17 to OT, and 1 to ST; 9 viruses could not be assigned to any species based on our stringent criteria. All these viruses are putative representative of new species (with only the exception of a sobemo-like virus that is 100% identical to a virus recently characterized in ST) and some belong to new higher-ranking taxa. These additions to the viral phylogeny suggest previously undescribed evolutionary niches. Most of Baltimore’s classes of RNA viruses were present (positive- and minus-strand and double-stranded RNA viruses), but only one DNA virus was identified in our collection. Repeated sampling in a subset of locations in 2019 and 2020 and further virus characterization in a subset of four thrips populations maintained in the laboratory allowed us to provide evidence of a locally persistent thrips core virome that characterizes each population.IMPORTANCE Harnessing the insect microbiome can result in new approaches to contain their populations or the damage they cause vectoring viruses of medical, veterinary, or agricultural importance. Persistent insect viruses are a neglected component of their microbiota. In this study, for the first time, we characterize the virome associated with the two model systems for tospovirus-transmitting thrips species, of utmost importance for the direct and indirect damage they cause to a number of different crops. The thrips virome characterized includes several novel viruses, which in some cases reveal previously undescribed clades. More importantly, some of the viruses we describe are part of a core virome that is specific and consistently present in distinct geographical locations monitored over the years, hinting at a possible mutualistic symbiotic relationship with their host.

Newly identified host range of viruses infecting species of the genus Allium and their distribution in six habitats in the Czech Republic

AbstractStudies on plant viruses are concentrated mainly towards crop diseases and little is known about viruses in wild and ornamental species. We surveyed viruses infecting 65 vegetable, wild, and ornamental Allium species cultivated or naturally occurring in the Czech Republic. Allium plants were collected from six habitat categories (botanical gardens, private gardens, cultivated fields, ornamentals from markets, cultivated plants of wild origin, wild origin). Samples were tested by ELISA and/or reverse transcription‐PCR for the presence of 15 viruses belonging to the genera Allexivirus, Carlavirus, Potyvirus, and Orthotospovirus. Of the 883 sampled plants, 63.4% were infected by at least one or more viruses. The infection rate of Allium samples differed depending on the habitat origin and phylogenetic relatedness of the hosts. Viruses were most frequently detected in cultivated species, with a high incidence of leek yellow stripe virus (LYSV), garlic common latent virus (GCLV), shallot virus X (ShVX), garlic virus A (GarV‐A), and garlic virus B (GarV‐B). Low infection rates and virus‐free samples were detected in species of wild origin. Composition of viruses belonging to the genus Allexivirus significantly differentiated the subgenus Melanocrommyum from other Allium subgenera. Mixed infections (51.1% of analysed plants) were widespread in most species. New host associations were observed for some viruses previously recorded in the Czech Republic. In addition, three viruses, shallot yellow stripe virus (SYSV), Impatiens necrotic spot virus (INSV), and iris yellow spot virus (IYSV), were detected for the first time on Allium species in the Czech Republic.

Analytical study of phenotypic and biochemical attributes of onion cultivars in relation to infestation of onion thrips, Thrips tabaci

• Anatomical features of onion cultivar suppress the population of Thrips tabaci . • Fatty alcohols influenced the formation of epicuticular wax in onion cultivars. • Biochemical characteristics of Onion Gawran contribute in resistance to T. tabaci . • Onion Gawran showed tolerance while Onion White was susceptible against T. tabaci. Onion thrips is a major threat to onion crop throughout the world. It is a potential vector of Iris yellow spot virus and causes significant economic damage to bulb production. Phenotypic and biochemical traits of onion cultivars were assessed against Thrips tabaci . Onion Gawran LR-241 (OG) cultivar was tolerant against the infestation of T. tabaci whereas Onion White (OW) was susceptible. Number and size of stomata, cuticle thickness, cell wall thickness and surface wax of onion leaves were studied with the help of scanning electron microscope and quantitative and qualitative analysis was carried out to estimate epicuticular wax and other bio-chemical components through GC/MS. Onion Gawran has thick cell wall, sharp and dense wax crystals, wider central angle and small sized stomata compared to other cultivars. Epicuticular wax components of OG cultivar were heptacosane (5.2%), octacosanol-1 (9.2%), 2-methyl octacosane (4.2%), heptadecanol-1 (5.2%), hexacosanol-1 (4.2%), azulene, 1,4-dimethyl-7-(1-methylethyl) (36.9%), hexadecanoic acid (1.95%), heptadecane (4.2%), triacontanol-1 (5.8%) and hentriacontanone-16 (23.40%). Azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) was only found 36.9% in OG but absent in other three cultivars. 2-methyl octacosane was absent in Poona Red Desi and OW cultivars. Hentriacontanone-16, 2-methyl octacosane, fatty alcohols (Octacosanol-1 and Triacontanol-1) and azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) were effective in the formation of epicuticular wax in onion cultivars. It implies that phenotypic and biochemical characteristics of OG cultivar proved as resisting features to T. tabaci .

Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines

Iris yellow spot (IYS) disease in onion (Allium cepa L.) is caused by onion thrips (Thrips tabaci L.) vectored Iris yellow spot virus (IYSV). The absence of cultivars that are resistant/tolerant to thrips and/or IYS is a challenge for onion bulb and seed production worldwide. To measure selection progress for reduced/delayed IYS symptom expression in onion breeding lines after two selection cycles, selections were performed in 2011 on previously evaluated lines that exhibited a reduced symptom expression after one selection cycle. Selected plants from each line were massed in a cage and the resulted progenies were evaluated in 2013 and 2014 along with their original populations and a susceptible check—’Rumba’. In some comparisons, the selection progress for delayed/reduced IYS symptom expression was observed for some breeding lines. Plants of most selected breeding lines exhibited less disease expression than plants of ‘Rumba’. For some selections, a low disease severity was observed even with a relatively high number of thrips per plant. These results suggest that further improvement might be achievable with additional cycles of selection.

First Report of Natural Infection by Capsicum Chlorosis Virus on Amaryllis (Hippeastrum hybridum) Plants from India

First Report of Natural Infection by Capsicum Chlorosis Virus on Amaryllis (<i>Hippeastrum hybridum</i>) Plants from India

The Major Biological Approaches in the Integrated Pest Management of Onion Thrips, Thrips Tabaci (Thysanoptera: Thripidae)

Abstract Thrips tabaci Lindeman is a cosmopolitan and polyphagous insect pest. It is known worldwide and recorded on more than 300 plant species. T. tabaci is a key pest of onion and several other crops, and its control is vital to the production and profitability of crops. If onion thrips population is not controlled, damage can reduce yield volume and quality. In addition to direct damage to the host plants, T. tabaci has been characterized as an asymptomatic vector of three devastating tospovirus species, such as Tomato spotted wilt virus, Iris yellow spot virus, and Tomato yellow ring virus. For this reason, several synthetic insecticides were used for control. However, these insecticides bring unwanted effects, like pesticide resistance, elimination of nontarget species, environmental pollution, and threats to human health. To solve the negative consequences of insecticides, biopesticides, such as plant secondary metabolites, entomopathogenic viruses, bacteria, fungi, and nematodes, have been recognized as effective alternatives. The use of plant-based insecticides and entomopathogenic control methods gained more attention in integrated pest management. Their strong side is lack of residues, saving beneficial insects and minimizing air and water pollution. Plant-derived compounds and entomopathogenic biological control agents offered a variety of biological modes of actions against onion thrips, such as repellency, feeding deterrence, anti-oviposition, fecundity deterrence, metamorphosis inhibition, and parasiting the host’s body.