Adult Thrips Research Articles

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.

A Maximum Dose Bioassay to Assess Efficacy of Spinetoram against Cowpea Thrip Megalurothrips usitatus in China.

The bean flower thrip Megalurothrips usitatus (Bagnall) is a severe pest on cowpeas and causes a 20-30% reduction in cowpeas in Hainan, China, with even complete crop failure in severe cases. Spinetoram is currently the most important pesticide against M. usitatus in cowpea production. In the main producing areas of cowpeas in Hainan, however, the efficacy of spinetoram against M. usitatus is not well known. In the present study, we employed the maximum dose bioassay to evaluate the efficacy of the mortality rates of adult thrips at F0 in spinetoram, freshly collected from 212 field populations of M. usitatus collected from 20 villages in the Yazhou District of Hainan. Our results showed that the mortality rates of these thrip populations exposed to spinetoram were from 3.31% to 100%. Among them, the mortality rates of 66.98% (142/212) of the populations exceeded 80%, while that of 33.96% (72/212) of the populations surpassed 90%. Only a small proportion of 0.47% (1/212) the populations exhibited a mortality rate below 10%, and 4.72% (10/212) displayed rates below 50%. Furthermore, significant differences were also observed in the mortality rates of thrips among different villages. Taken together, the maximum dosage bioassay method is a rapid and easily implemented approach providing valuable insights into the field efficacy of insecticides and offers guidance in determining the optimal dosage required in the field. Spinetoram is still effective against M. usitatus in the main producing areas of cowpeas in Hainan, but caution should be exercised in its combined use with other methods to reduce potential resistance.

Field survey of reproductive modes and sodium channel mutations associated with pyrethroid resistance in Thrips tabaci.

Using PCR-Restriction Fragment Length Polymorphism (RFLP) with mitochondrial cytochrome c oxidase subunit I sequences, we examined the reproductive modes of female adults of Thrips tabaci collected at 54 sites across Japan. Results showed the presence of heteroplasmic insects harboring mitochondria associated with arrhenotoky and thelytoky. Using the insects, we also applied PCR-RFLP to examine the genotypes for the amino acid mutation (T929I) site involved in pyrethroid resistance. Findings showed the presence of thelytokous heterozygotes under the circumstance that most arrhenotokous insects are resistant homozygotes, and many thelytokous insects are susceptible homozygotes. These results suggest that, in the field, genetic exchange occurs between insects through of both reproductive modes. A survey of the genotypes for the other amino acid mutations using nucleotide sequencing showed a decline of insects with an M918T and L1014F pair and an increase of insects with M918L. These results suggest the evolutional progression of amino acid mutations associated with pyrethroid resistance in T. tabaci.

Thrips species occurring in red raspberry, Rubus idaeus L., in South Norway

Aim of study: Thrips in raspberry crops are receiving attention in Scandinavian raspberry production because of the increasing sighting of their presence in the flowers. Specific information on thrips species occurring in raspberry and their damage potential is scarce, making thrips management challenging. Therefore, this study aimed to identify thrips in the flowers of cultivated raspberry, Rubus idaeus L., in South Norway. Area of study: Sogndal, Luster and Frogn, Southern Norway Material and methods: Adult thrips were sampled from eight commercial raspberry orchards in the counties Vestland and Viken in June-July 2022. Thrips were mounted using Hoyer’s medium and a total of 213 specimens were morphologically identified. Main results: Five species of thrips were found, Thrips fuscipennis Haliday, Thrips major Uzel, Thrips flavus Schrank, Thrips vulgatissimus Haliday and Thrips brevicornis Priesner. Most specimens were T. flavus, followed by T. fuscipennis and T. vulgatissimus. Research highlights: Among the five species found, only T. fuscipennis has previously been reported in cultivated raspberry, but all five species are associated with flowers of many plants. The findings imply a larger and more geographically varied thrips fauna on raspberry than currently documented. This should be taken into account in future studies on thrips management in raspberry.

Virus-vectoring thrips regulate the excessive multiplication of tomato spotted wilt virus using their antiviral immune responses.

The tomato spotted wilt virus (TSWV) is a member of the Tospoviridae family and has an negative/ambisense single-stranded RNA genome. Frankliniella occidentalis and F. intonsa are known to be dominant pests in Capsicum annuum (hot pepper) and can cause damage to the plant either directly by feeding, or indirectly by transmitting TSWV in a persistent and propagative manner, resulting in serious economic damage. This study compared the immune responses of two different thrips species against TSWV infection by transcriptome analysis, which then allowed the assessment of antiviral responses using RNA interference (RNAi). Both adult thrips shared about 90 % of the transcripts in non-viruliferous conditions. Most signal components of the immune pathways were shared by these two thrips species, and their expression levels fluctuated differentially in response to TSWV infection at early immature stages. The functional assays using RNAi treatments indicated that the Toll and JAK/STAT pathways were associated with the antiviral responses, but the IMD pathway was not. The upregulation of dorsal switch protein one supported its physiological role in recognizing TSWV infection and triggering the eicosanoid biosynthetic pathway, which mediates melanization and apoptosis in thrips. In addition, the signal components of the RNAi pathways fluctuated highly after TSWV infection. Individual RNAi treatments specific to the antiviral signalling and response components led to significant increases in the TSWV amount in the thrips, causing virus-induced mortality. These findings suggest that immune signalling pathways leading to antiviral responses are operating in the thrips to regulate TSWV litres to prevent a fatal viral overload. This study also indicates the differential antiviral responses between the TSWV-transmitting F. occidentalis and F. intonsa.

Relevance of diet diversification in the coexistence between Orius laevigatus and Amblyseius swirskii: prey switching and intraguild predation

AbstractOmnivores obtain resources from more than one trophic level, choosing food based on quantity and quality. They usually engage in intraguild predation (IGP) when prey is scarce. Orius laevigatus is an example of omnivore that becomes superior predator of the predatory mite Amblyseius swirskii when released in a combined system under low levels of the preferred prey, the thrips Frankliniella occidentalis. Here, we test two genetically enhanced O. laevigatus strains for bigger size and better fitness feeding on pollen (BIG30 and 2POL-11, respectively), hence with a wider dietary diversification, to elucidate the potential effects on prey preference and IGP on the predatory mite, in comparison with a commercial population of O. laevigatus. To do that, predation rates were registered on adult phytoseiids solely or in a choice situation at different availability ratios of adult thrips under laboratory conditions. The effect of pollen as supplemental food on IGP and prey preference was examined, too. We found that our two enhanced lines killed up to 9% less predatory mites and fed preferably on adult thrips, compared to the commercial population. While BIG30 showed a significantly higher total predation rate, killing up to 150% more adult thrips, 2POL-11 is defined as an efficient user of resources, switching between different prey and pollen showing low IGP. Pollen supplementation had a significant effect on reducing IGP, but only for 2POL-11 the influence on prey preference was significant. The theory of intraguild predation and the impact of prey switching on food webs and biological control strategies are also discussed.

Identification of aggregation pheromones released by the stick tea thrips (Dendrothrips minowai) larvae and their application for controlling thrips in tea plantations.

The stick tea thrips, Dendrothrips minowai Priesner, is one of the most important sucking pests that seriously infest tea plants (Camellia sinensis) in China. Given that D. minowai exhibit aggregation behaviors in tea plantations, this study evaluated the potential of aggregation pheromones for their control. H-tube olfactometer assays showed that D. minowai larvae, adult females and adult males were significantly attracted to larvae rather than adult females and males under laboratory conditions. Subsequent gas chromatography-mass spectrometry analysis of volatiles from larvae, identified two larva-specific components: dodecyl acetate and tetradecyl acetate. Electrophysiological and behavioral experiments confirmed the positive response of females and males to dodecyl acetate, tetradecyl acetate, and their blend (1:1.5). Deployment of these aggregation pheromones on sticky traps resulted in a 1.2- to 3.0-fold increase in the capture of D. minowai adults compared with control traps. In addition, deployment of sticky traps baited with these aggregation pheromones within tea plantations resulted in a noteworthy reduction in the population of adult thrips per 100 leaves, 10 days following trap deployment. The reduction ranged from 29% to 59%, in comparison with the control. D. minowai larvae produce aggregation pheromones, dodecyl acetate and tetradecyl acetate, that can be useful for controlling tea thrips. © 2023 Society of Chemical Industry.

An analysis of Thysanoptera associated with the flowers of some stone fruits in Mersin Province (Türkiye): composition, distribution, population dynamics and damage status

The distribution, abundance and damage status of Thysanoptera species were investigated in two different regions of Mersin Province, Türkiye between 2020 and 2021. A total of 18 Thysanoptera species were determined, with Thrips major Uzel, 1895 and Frankliniella occidentalis (Pergande, 1895) (Thysanoptera: Thripidae) being the most common. While nectarine had the highest diversity of habitats for thrips, plum displayed greater richness in terms of species composition. Adult thrips primarily inhabited flowers while T. major larvae were present during petal fall periods. No larvae of F. occidentalis or Thrips tabaci Lindeman,1889 (Thysanoptera: Thripidae) were found on the plant parts sampled throughout the samplings. Although no visible signs of damage by adult thrips were observed on the flowers, typical damage in the form of silvery scars appeared on the young fruits of nectarines and plums. The average rate of scarred fruit of nectarines or plums varied between 2-7%. Finally, T. major was the main pest thrips species responsible for damaging fruits of the plums and nectarines in Mersin.

Taxonomic review and illustrated key to identify species of Thysanoptera in subfamily Panchaetothripinae (Thripidae) from the Philippines

The paper provides a review of 16 species in 12 genera under subfamily Panchaetothripinae (Thysanoptera: Thripidae) from the Philippines including new host plant records for Selenothrips rubrocinctus (Giard). Identification keys to genus and species were developed using morphology-based diagnostics of adult female thrips. Photomicrographs of female, and male thrips when available are provided. Reviewed and redefined are the morphological characteristics of Astrothrips aucubae Kurosawa, Astrothrips globiceps (Karny), Astrothrips tumiceps Karny, Caliothrips striatopterus (Kobus), Copidothrips octarticulatus (Schmutz), Elixothrips brevisetis (Bagnall), Helionothrips annosus Wang, Helionothrips guttatus Reyes, Helionothrips kodaliphilus (Ramakrishna & Margabandhu), Heliothrips haemorrhoidalis (Bouche), Hemingia glandula Reyes, Panchaetothrips stepheni Reyes, Phibalothrips peringueyi (Faure), Retithrips javanicus Karny, Rhipiphorothrips pulchellus Morgan, and Selenothrips rubrocinctus (Giard). Species identity confirmation using molecular techniques is recommended for the three species of Helionothrips Bagnall. All 16 species of thrips infest crop plants, fruit trees, grasses, and ornamentals. Caliothrips striatopterus (Kobus), Heliothrips haemorrhoidalis (Bouche), and Selenothrips rubrocinctus (Giard) are pests of mangosteen, and other high value crops in the Philippines.

Comparative Study of Integrated Pest Management and Farmer's Standard Practices for Controlling Chrysanthemum Thrips under Plastic House

Thrips is an important worldwide cause of severe damage to various host plants, especially chrysanthemums. Current management still relies on synthetic insecticides to control thrips. However, these pesticides harm the environment and promote thrips resistance. The study aimed to compare integrated pest management (IPM) and farmer’s standard practices to control <em>Thrips parvispinus</em> on two chrysanthemum varieties and calculate the cost-benefit ratio of both pest control practices. Two chrysanthemum cultivars were planted in plastic houses to compare IPM and farmer’s standard practices. The observed variables included thrips density, attack and damage rates, cut flower yield, and natural enemies abundance. Data were analyzed using ANOVA, and Tukey's HSD test identified significant differences at a 5% level. The results showed that the population of <em>T. parvispinus</em> nymphs was higher (78%) than adults. The highest adult thrips population emerges when chrysanthemums achieve the flowering phases. This study reveals that the control effects of IPM were not different from farmer’s standard practices. A holistic approach integrating several management strategies successfully controlled the thrips population while producing high-quality crops with minimal aesthetic damage. The IPM strategy against thrips showed a competitive cost and reduced synthetic insecticide applications without decreasing the quality and productivity of chrysanthemums.

Molecular characterization and incidence of new tospovirus: Soybean Vein Necrosis Virus (SVNV) in Egypt.

Field survey study was conducted season (2017). Soybeans and weeds were weekly sampled randomly. Thrips adults were identified and counted. Detection of the virus isolate and the natural incidence was determined using; Mechanical transmission, host range, DAS-ELISA, RT-PCR. The natural incidence thrips individuals was detected depending on the SVNV% in thrips individuals and weeds hosts. Ten thrips species were associated with soybean plants in the field. The most abundant species was T. tabaci, average 256.5 average no.of individuals, followed by F. occidentalis (142.5 average no. of individuals), then N. variabilis (86.6/ average no. of individuals). Fourteen thrips species occurred on 5 legumes field crops and 41 weed plant species within soybean field. The highest average number 40.6.of individuals were recorded on Ammi majus. While the lowest one 3.3 average no. of individuals were on Urtica urens. Only 21diagnostic plant species were susceptible to infection with SVNV. G. max and Vigna radiate, were the highest percentage of infection 80% followed by V. unguilata & N. benthamiana, 75%. Egyptian isolate of Soybean vein necrosis virus (SVNV) in this study showed a high degree of similarity and it is closely related to TSWV from Egypt (DQ479968) and TCSV from USA (KY820965) with nucleotide sequence identity of 78%. Four thrips species transmitted SVNV (F. fusca 4.0%, F. schultzei 4.3%, F. tritici 3.3% and N. variabilis 68.0% transmission). Both C. phaseoli and M. sjostedti can acquire the virus but unable to transmit it. The following species; T. tabaci, F. occidentalis, S. dorsallis and T. palmi cannot acquire or transmit SVNV. The incidence of SVNV in the field started by the end of July then increased gradualy from 12.7 to 71.3% by the end of the season. In conclusion, few thrips individuals invaded soybean crops are enough to transmit high rate of SVNV within the crop. Furthermore, several vector species are also abundant on weeds, which are the major sources of soybean viruses transmitted to the crops. This information might be important for control and reduce the incidence of SVNV infection.

Composition and distribution of Thysanoptera (Insecta) in the area of Balcalı, Adana Province, Türkiye

This study was conducted to identify thrips (Insecta: Thysanoptera) species in the Balcalı area of Adana Province, Türkiye, known as a polyculture area having diverse topographic features. Thrips were extensively collected by the tapping method from awide range of agricultural crop plants during 2019-2020. A total of 1150 adult thrips individuals were collected, representing 24 identified species. Among them, the most prevalent and abundant species were the cotton thrips, Thrips tabaci Lindeman and the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). These two species showed varying population dynamics based on the flowering patterns of the plants sampled. Thankfully, no thrips damage was observed on the sampled plants. Although invasive pest thrips species such asThrips hawaiiensis (Morgan) and Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae) were found in low numbers, and both of them were collected mostly from flowers of sesame and green pepper plants. A low number of predatory thrips belonging to geniuses, Aeolothrips (Aeolothripidae) and Scolothrips (Thripidae) were detected on beans, potatoes and cotton after March.

Study of the efficacy of spraying fructose to enhance resistance of chili culture to thrips (thysanoptera: thripidae) in a greenhouse in Biskra, Algeria

ABSTRACT Thrips are insect pests that threaten pepper crops. This study, conducted in the arid Biskra region of Algeria, evaluated the impact of applying infra-doses of fructose at the concentrations (0, 0.1, 1, 10, and 100 ppm) on enhancing the resistance of chilli pepper plants to thrips. We monitored the population of thrips after 24, 48, 72 hours, 7 and 21 days post treatment application for each concentration. The same infra-doses were re-applied using the same protocol. The data revealed that spraying fructose at 100 ppm was the most effective, reducing thrips population significantly after 48 hours (F = 61.383, P < 0.05), resulting in an average of 52 ± 10.56 adult thrips per plant.

Dehydration yields distinct transcriptional shifts associated with glycogen metabolism and increases feeding in the western flower thrips, Frankliniella occidentalis

AbstractWe examined water balance characteristics and the influence of desiccating conditions on the physiology and behavior of adult western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Western flower thrips are globally invasive and likely to contend with shifts in water availability across their expansive geographic range. Basic water balance characteristics, including water mass and dry mass, were established for adult males and females, revealing a distinct sexual dimorphism wherein females are larger, and males retain a larger percentage of their body mass as water. Males lose relative water mass more quickly and their survival times are shorter compared to females. RNA‐seq analysis identified significant enrichment of a multitude of factors including carbohydrate transport and metabolism in dehydrated males and females. This was validated by altered glycogen levels, suggesting a rapid depletion in glycogen during dehydration. The probability of thrips feeding significantly increases when desiccation occurs, potentially to replenish water content and nutrient reserves. Our results establish the fundamental water balance characteristics of adult thrips and indicate that dehydration significantly influences the survivorship and feeding behavior of thrips; all of which being crucial factors that contribute to their capacity as vectors for plant pathogens.

Thrips (Insecta: Thysanoptera) Species in Pepper Fields in Tokat Province, Türkiye

Abstract: Thrips (Insecta: Thysanoptera) species in pepper fields was determined in Tokat Province, Türkiye in 2021-2022. The density of thrips began to rise once the leaves emerged in late May, and the collection of thrips species started in June to October. To conduct regular samplings of thrips that were infesting pepper fields, flowers were collected and placed in plastic tubes (50 ml) filled with ethyl alcohol at a concentration of 60%. The densities of thrips populations and the resulting damage caused by thrips attacks on different plant components (such as flowers, leaves, and fruits) were evaluated through the examination of a randomly chosen 25 samples for each plant part during each sampling period. The assessment encompassed various thrips families belonging to the order Thysanoptera, specifically, families, Thripidae, Aeolothripidae, and Phlaeothripidae. A total of 7 Thysanoptera species were identified in this study. The species were Frankliniella occidentalis (Priesner, 1932), Thrips tabaci Lindeman), 1895, Thrips meridionalis (Priesner 1926) and Chirothrips manicatus (Haliday, 1836) in Thripidae family, and Aeolothrips intermedius (Bagnall, 1934) and Aeolothrips fasciatus (Linnaeus, 1758) in Aeolothripidae family, and Haplothrips aculeatus (Fabricius, 1803) in Phlaeothripidae family. Both adult and larval thrips were collected mainly from the flowers sampled In this study, the dominant species was F occidentalis in pepper fields in Tokat Province.

Integrated Effect of Plastic Mulches and Biorational Insecticides in Managing Tomato Chlorotic Spot Virus (TCSV) and Its Vector Thrips in Tomatoes.

In the USA, tomato chlorotic spot virus (TCSV) was first identified in Miami-Dade County of Florida in 2012. This viral disease is transmitted by thrips (Thysanoptera: Thripidae) of different species, imposing a serious threat to the entire tomato production in the state. Both cultural and chemical control techniques could be essential tools to combat this vector-borne disease. In the present two-year-long study, we determined the effect of different types of plastic mulches and biorational insecticides on managing thrips and TCSV. Results from the leaf and flower samples showed a significantly lower adult thrips population in Entrust®SC treated tomatoes than in other treated and untreated tomatoes in 2018. Silver on black and silver on white reflective plastic mulches significantly reduced the adult thrips population in 2018. In both study years, marketable yield was significantly higher in tomatoes treated with Entrust®SC and reflective plastic mulches than in other treatments. The incidence of TCSV was significantly reduced in tomatoes treated with Entrust®SC and reflective plastic mulches than the untreated control in 2018. Marketable yield was negatively correlated with the thrips population, as observed from the Pearson correlation coefficient analysis. This research describes a potentially viable management program for thrips and thrips-transmitted TCSV.

Predation potential and life history of three nabid species as biological control agents of pests in Canadian greenhouses

Nabids are hemipteran generalist predators commonly associated with agroecosystems. In this study, the predation rate of Nabis americoferus Carayon, N. roseipennis Reuter, and Hoplistoscelis pallescens Kerhzner on several common greenhouse pests was assessed in the laboratory, compared to the most closely related commercially available predator in North America, Dicyphus hesperus Knight (Heteroptera: Miridae). In addition, life history parameters of the nabids were determined to estimate their capacity for population increase, an important data set when considering their mass rearing and population establishment in crops. Our results showed that the three nabid species are generally more voracious predators than D. hesperus, especially when fed adult green peach aphids, adult western flower thrips and adult greenhouse whiteflies. Dicyphus hesperus preyed more on two spotted spider mites and greenhouse whitefly nymphs. Nabis americoferus consumed more western flower thrips larvae than all other species. Of the three nabids, N. americoferus also performed significantly better as a predator of western flower thrips. Additionally, N. americoferus had a significantly shorter egg to adult development time, and had a shorter pre-oviposition period than the other two species. Based on its predation capacity and favourable life history characteristics, N. americoferus was selected for further development as a new biological control agent for the North American market.

Balcalı, Adana’da dış mekan süs bitkilerinde thrips (Thysanoptera) kompozisyonu, bulunma sıklıkları ve yoğunlukları

Objective: Phytophagous thrips are among the important pests of ornamental plants. Unlike other studies, in this study, thrips species mostly in perennial arboreal and shrub plants were investigated in the Balcalı location of Adana province, Türkiye in 2019-2020. Materials and Methods: Thrips were collected from ornamental plants by shaking method, and the collected individuals were stored in 60% ethyl alcohol. Results and Conclusion: Eleven harmful and two beneficial thrips species were determined from 788 adult thrips individuals collected. The most common and abundant in dense numbers, respectively, Hot pepper thrips, Thrips hawaiiensis (Morgan, 1913), Western flower thrips, Frankliniella occidentalis (Pergande, 1895) that they are important pests, and Gold-tipped tubular thrips, Haplothrips gowdeyi (Franklin, 1908) were determined and constituted 58.6%, 27.5% and 4.0% of the total individuals, respectively.

大阪府におけるミナミキイロアザミウマに対する各種薬剤の殺虫効果

We used the leaf-dipping method to determine the toxicity of 10 insecticides on the adult melon thrips, Thrips palmi, collected from Kanan Town and Tondabayashi City in Osaka Prefecture. Flometoquin and fluxametamide were effective against T. palmi. The toxicity of nitenpyram and emamectin benzoate depended on the collected population. Acetamiprid, spinetoram, abamectin, chlorfenapyr, cyantraniliprole, and pyridalyl showed low corrected mortality in all populations.

Use of prohydrojasmon to suppress Frankliniella occidentalis and tomato spotted wilt virus in chrysanthemums

We evaluated the suppressive effect of prohydrojasmon (PDJ) on Frankliniella occidentalis and tomato spotted wilt virus (TSWV) in chrysanthemums under semi-commercial conditions. The overhead sprinkling of plants with PDJ did not suppress the initial colonization of plants by released adult thrips. However, it significantly reduced subsequent feeding damage on leaves and the reproduction of larval offspring. Rates of 1 and 2 L/m2 of 0.8 mM PDJ equally suppressed F. occidentalis and feeding damage without phytotoxic effects, although 3 L/m2 reduced plant growth. Frequencies of 2 and 3 applications of PDJ at different intervals had similar inhibitory effects on F. occidentalis, suggesting the possibility of low-frequency, labor-saving applications in chrysanthemums. Weekly applications suppressed the occurrence of TSWV transmitted by viruliferous adult thrips dispersed from inoculum sources to a degree consistent with that of feeding damage, so PDJ might inhibit primary infection via disruption of feeding behavior. All our findings suggest that PDJ offers a valuable option for controlling F. occidentalis and orthotospovirus diseases transmitted by it in chrysanthemum production greenhouses.