Occidentalis Adults Research Articles

Lecanicillium attenuatum infection and effects on the reproduction of Frankliniella occidentalis

ABSTRACT Frankliniella occidentalis, western flower thrips, is an invasive pest that seriously damages economic crops such as vegetables, flowers, and fruit trees because of its high fecundity, short generation cycle, and strong adaptability. Lecanicillium is an important entomopathogenic fungus, characterised by its wide host range, high pathogenicity, and environmental safety. It plays an important role in the environmentally friendly management of F. occidentalis. This study clarifies whether L. attenuatum infects F. occidentalis and affects its reproduction. The results of scanning electron microscope showed that conidia of L. attenuatum were attached to many parts of thrips adult after 1 h of treatment with 10^8 conidia/mL, and most F. occidentalis were covered by hyphae after 72–120 h. The cumulative mortality rate of the second instar larvae of the F1, F2, and F3 generations exceeded 60% on the seventh day post-infection and that of female adults was higher than 90% when treated by L. attenuatum with 10^8 conidia/mL. Simultaneously, L. attenuatum had strong sublethal effects on the surviving thrips. Indeed, the number of eggs deposited and the lifespan of female adults decreased considerably after the second instar larvae of F. occidentalis were treated with L. attenuatum, and had the impaction on the thrips offspring too. Altogether, our data suggested that L. attenuatum not only exhibited a high degree of pathogenicity towards F. occidentalis second instar larvae and adults but also affected the longevity and reproduction of surviving thrips.

Leptoglossus occidentalis Heidemann, 1910 (Hemiptera Coreidae) in Türkiye Its distribution, life cycle, and fungal associations

In this study, the distribution, life cycle and associations with fungi of the alien invasive species Leptoglossus occidentalis Heidemann, 1910 (Hemiptera: Coreidae) in Türkiye were investigated. During the study between 2019 and 2021, we found that the pest has spread almost all over Türkiye. We recorded the presence of the species in 35 provinces. The biological data obtained in the study were divided into ecologically similar sub-regions (Ankara-Çankırı-Kırşehir, Artvin, Isparta-Burdur, Izmir-Aydın-Manisa-Muğla-Antalya) in order to reveal the life cycle of the species. Additionally, host plant and insect samples were examined for the presence of Diplodia sapinea (Fr.) Fuckel (pine shoot blight agent) and entomopathogenic fungi species through morphological and molecular identification methods. Consequently, we found that L. occidentalis has two generations in Türkiye. Timing of the first flight was in early May-mid June and the second generation was from mid-July to late August. Although D. sapinea was detected in some of the sampled host plant tissues, it could not be isolated from L. occidentalis individuals. Accordingly, we did not find any evidence that L. occidentalis vectors D. sapinea although the insect and the fungus cooccurs in sampling areas. On the other hand, its vector potential cannot be ruled out especially during rainy periods. This potential remains as a hypothesis for future studies. Although we detected 25 fungal species isolated from L. occidentalis adults, none of them were entomopathogenic fungal species.

Dual Guardians of Immunity: FoRab10 and FoRab29 in Frankliniella occidentalis Confer Resistance to Tomato Spotted Wilt Orthotospovirus.

Rab GTPase is critical for autophagy processes and is implicated in insect immunity against viruses. In this study, we aimed to investigate the role of FoRabs in the autophagic regulation of antiviral defense against tomato spotted wilt orthotospovirus (TSWV) in Frankliniella occidentalis. Transcriptome analysis revealed the downregulation of FoRabs in viruliferous nymph and adults of F. occidentalis in response to TSWV infection. Manipulation of autophagy levels with 3-MA and Rapa treatments resulted in a 5- to 15-fold increase and a 38-64% decrease in viral titers, respectively. Additionally, interference with FoRab10 in nymphs and FoRab29 in adults led to a 20-90% downregulation of autophagy-related genes, a decrease in ATG8-II (an autophagy marker protein), and an increase in the TSWV titers by 1.5- to 2.5-fold and 1.3- to 2.0-fold, respectively. In addition, the leaf disk and the living plant methods revealed increased transmission rates of 20.8-41.6 and 68.3-88.3%, respectively. In conclusion, FoRab10 and FoRab29 play a role in the autophagic regulation of the antiviral defense in F. occidentalis nymphs and adults against TSWV, respectively. These findings offer insights into the intricate immune mechanisms functional in F. occidentalis against TSWV, suggesting potential targeted strategies for F. occidentalis and TSWV management.

Rickettsia species identified in adult, host-seeking Dermacentor occidentalis (Acari: Ixodidae) from Baja California, Mexico, and Oregon and Washington, United States.

The Pacific Coast tick (Dermacentor occidentalis Marx, 1892) is a frequently encountered and commonly reported human-biting tick species that has been recorded from most of California and parts of southwestern Oregon, southcentral Washington, and northwestern Mexico. Although previous investigators have surveyed populations of D. occidentalis for the presence of Rickettsia species across several regions of California, populations of this tick have not been surveyed heretofore for rickettsiae from Baja California, Oregon, or Washington. We evaluated 1,367 host-seeking, D. occidentalis adults collected from 2015 to 2022 by flagging vegetation at multiple sites in Baja California, Mexico, and Oregon and Washington, United States, using genus- and species-specific assays for spotted fever group rickettsiae. DNA of Rickettsia 364D, R. bellii, and R. tillamookensis was not detected in specimens from these regions. DNA of R. rhipicephali was detected in D. occidentalis specimens obtained from Ensenada Municipality in Baja California and southwestern Oregon, but not from Washington. All ompA sequences of R. rhipichephali that were amplified from individual ticks in southwestern Oregon were represented by a single genotype. DNA of the Ixodes pacificus rickettsial endosymbiont was amplified from specimens collected in southwestern Oregon and Klickitat County, Washington; to the best of our knowledge, this Rickettsia species has never been identified in D. occidentalis. Collectively, these data are consistent with a relatively recent introduction of Pacific Coast ticks in the northernmost extension of its recognized range.

First report of Leptoglossus occidentalis (Hemiptera: coreidae) feeding on Rubus (Rosaceae) fruit

Abstract The western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae), feeds extensively on the seeds of conifer trees within both its endemic range west of the Rocky Mountains and its expanding introduced range throughout eastern North America, South America, Europe, and Asia. Its damage to conifer seed challenges seed production in natural stands and in orchards that produce seed for forest regeneration and food. In summer 2023, hundreds of L. occidentalis adults were observed feeding on the berries of two cultivated blackberry, Rubus fruticosus Linnaeus (Rosaceae), vines on southern Vancouver Island, British Columbia, Canada. The adults were observed over a period of approximately six weeks, and their stylets were seen penetrating drupelets and causing subsequent damage. Identification was confirmed based on morphological and molecular (CO1 DNA barcoding) methods. To our knowledge, this is the first verifiable report of L. occidentalis feeding on a Rosaceae host, suggesting the insect’s potential for damaging agricultural systems.

Enhanced β-glucosidase in Western flower thrips affects its interaction with the redox-based strategies of kidney beans under elevated CO2.

β-Glucosidase is validated as an elicitor for early immune responses in plants and it was detected in the salivary glands of Frankliniella occidentalis in previous research. Seven differentially expressed genes encoding β-glucosidase were obtained by comparing the transcriptomes of F. occidentalis adults grown under two different CO2 concentrations (800 vs. 400 ppm), which might be associated with the differences in the interaction between F. occidentalis adults and its host plant, Phaseolus vulgaris under different CO2 levels. To verify this speculation, changes in defense responses based on the production and elimination of reactive oxygen species (ROS) in P. vulgaris leaves treated with three levels of β-glucosidase activity under ambient CO2 (aCO2 ) and elevated CO2 (eCO2 ) were measured in this study. According to the results, significantly higher levels of ROS were noticed under eCO2 compared to aCO2 , which was caused by the increased β-glucosidase activity in thrips due to increased cellulose content in P. vulgaris leaves under eCO2 . Together with the lower activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)in injured leaves under eCO2 , P. vulgaris leaves would be negatively affected on redox-based defense by eCO2 , thus facilitating thrips damage under climate change.

Biocontrol of the western conifer seed bug, Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) using indigenous entomopathogenic fungi

Abstract Background The western conifer seed bug, Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), is one of the major pest in seed orchards of various conifers, significantly affects pine seed production and causes economic damage. Biological control by natural enemies has been well studied, but its entomopathogens have been poorly studied. In this study, the efficacy of twelve indigenous entomopathogenic fungi belonging to the genera Beauveria, Metarhizium, and Isaria on L. occidentalis adults was investigated. Results All isolates were found to be pathogenic at a concentration of 107 conidia/ml where the virulence ranged from 16 to 90%. Moreover, the virulence of two Metarhizium flavoviride isolates (As2 and As18) reached 90% at 107 conidia/ml concentration. In addition, L. occidentalis treated with M. flavoviride As18 (LT50 = 2.53 days) died more rapidly than with M. flavoviride As2 (LT50 = 5.83 days) at the same treated concentration. For concentration-dependent virulence for isolate As18, five conidia concentrations: 103, 104, 105, 106, and 107 conidia/ml were used. Also, the median lethal (LC50) value of As18 isolate was estimated to be 7.61 × 103 conidia/ml after 10 days of treatment. Since L. occidentalis is known to accumulate during overwintering, conidial transmission among adults was investigated. Unfortunately, horizontal transmission between adults did not occur. Conclusion The isolate M. flavoviride As18, which had low LC50 and LT50 values, appeared to be a promising biological control agent against L. occidentalis. This isolate should be formulated as a myco-insecticide and tested under field conditions in further studies.

Movement of Ixodes pacificus and Dermacentor occidentalis (Acari: Ixodidae) adult ticks in chaparral under natural conditions in Northern California, U.S.A.

The movement of Ixodes pacificus and Dermacentor occidentalis adult ticks down a hill slope under natural conditions was investigated using the mark-release-recapture (MRR) method. We evaluated the movement of host-seeking adult ticks down a hill slope to determine if ticks travel downhill from an uphill area to trail margins below. During the tick seasons in 2016-2018, the ticks were collected by flagging, marked with paint, released at a predetermined location, and recaptured by weekly flagging. Of the 188 female and 114 male I. pacificus marked and released 30 m above the trail in 2016, 11 (5.8%) females and one (0.9%) male were recaptured at the trail. In 2017, of the 71 female and 52 male I. pacificus, none were recaptured. In 2018, nine (3.6%) female and one (0.4%) male I. pacificus were recaptured of the 247 female and 287 males marked and released. Fifteen (18.5%) female and six (7.3%) male D. occidentalis were recaptured of the 81 females and 82 males marked and released in 2017. The trail deterred further movement with only 0.6% of I. pacificus and 8.3% of D. occidentalis recaptured on the opposite side of the trail. This study demonstrated that some I. pacificus and D. occidentalis adults found along the uphill side of trails may have originated from an area 30 m from the trail margin, some travelling at a rate of 1.6-1.9 m/day under natural conditions in chaparral.

Enhanced biocontrol services in artificially selected strains of Orius laevigatus

Augmentative biological control in protected crops relies mainly on omnivorous predators. Their performance as biological control agents (BCA) depends on several characteristics of the species, which in turn may differ among strains within a species. We have recently reported the achievement of two Orius laevigatus (Hemiptera: Anthocoridae) strains showing a significant larger body size or better fitness when feeding on pollen, two characteristics having a key impact on field performance. However, selection towards a specific trait might result in trade-offs, such as reduced predation capacity, which may impair control efficiency. Therefore, the predation capacity of these selected populations was tested in laboratory as a first step prior to its field use. Functional response to different densities of Frankliniella occidentalis (Thysanoptera: Thripidae) (adults and larvae) and Myzus persicae (Hemiptera: Aphididae) (nymphs) were studied in the large-sized and pollen-tolerant O. laevigatus strains in comparison with commercial and wild populations. A type-II functional response was observed regardless of the population. Body size was significantly related to thrips but not to aphid predation. The large-sized strain showed a superior predation capacity, both on thrips larvae and especially on adult thrips, although not on aphids. Therefore, the larger body size of the selected strain may increase its effectiveness as BCA of thrips. Regarding the pollen-tolerant strain, no trade-offs were observed in predation rates on adults or larvae of thrips, but it showed higher predation capacity on aphid nymphs, suggesting an expanded prey range. Implications of such enhanced biocontrol services on crop protection are also discussed.

Predator-prey interactions and life history of Orius laevigatus and O. majusculus feeding on flower and leaf-inhabiting thrips

Thrips (Thysanoptera: Thripidae) are major pests in horticulture worldwide. Longstanding biological control strategies that have been developed for flower thrips such as Frankliniella occidentalis (Pergande) are being disrupted by the recent introduction of leaf-inhabiting thrips such as Echinothrips americanus Morgan and Thrips setosus Moulton in Northern Europe. In this study, we evaluated the predator–prey interactions, predation capacity, juvenile development and adult reproduction of the two commercial anthocorid predators Orius laevigatus (Fieber) and Orius majusculus (Reuter) (Hemiptera: Anthocoridae) on these thrips. In behavioral assays, predators were more successful in subduing and consuming sedentary leaf-inhabiting thrips adults compared to the highly mobile F. occidentalis. Furthermore, O. laevigatus was more successful in subduing prey compared to the bigger predator O. majusculus. Female adults of O. laevigatus and O. majusculus killed 18 and 20 F. occidentalis adults, respectively, in 24 h, while the kill rate was around two times higher when predators were offered E. americanus or T. setosus as prey. Developmental and reproductive parameters of both Orius predators were more favorable when feeding on the leaf-inhabiting thrips compared to F. occidentalis. This was further evident in the higher intrinsic rates of increase (rm) we recorded on a diet of E. americanus compared to F. occidentalis (0.162 and 0.148 females/female/day for O. laevigatus, respectively; 0.148 and 0.127 for O. majusculus, respectively). Our findings show that E. americanus and T. setosus constitute high quality prey for anthocorid predators, highlighting the potential of these predators for effective pest control.

Elevated CO2 aggravates invasive thrip damage by altering its host plant nutrient and secondary metabolism

As atmospheric CO2 concentration continues to increase, plants using CO2 as raw materials for photosynthesis will inevitably be affected, which in turn affects the life history and behavior of herbivorous insects. Our previous research has shown increased food intake and aggravated damage of western flower thrips, Frankliniella occidentalis to kidney bean (Phaseolus vulgaris) caused by elevated CO2 (eCO2), however the molecular mechanism of this phenomenon is unclear. In this study, the comparative transcriptome analysis combined with corresponding phenotypic changes were studied to reveal the molecular mechanism of interaction between F. occidentalis and P. vulgaris under eCO2. Inferred from the results, eCO2 had different degrees of inhibition to the defense responses caused by thrips infestation in P. vulgaris leaf sap based on nutrients, plant hormones and secondary metabolites, making P. vulgaris leaves less resistant to thrips under eCO2 compared to ambient CO2 (aCO2). Besides, the contents of glucose, trehalose, triglycerides and free fatty acids in F. occidentalis adults increased significantly after feeding on the P. vulgaris leaf sap with significantly increased soluble sugars content under eCO2, which might lead to glucolipid metabolic disorders and increased food intake of F. occidentalis adults. The results indicated that decreased plant defense of P. vulgaris and increased food intake of F. occidentalis adults were combined to aggravate the thrips damage under eCO2, providing a theoretical basis for future occurrence trend of thrips under eCO2.

Could Broccoli and Cauliflower Influence the Dispersal Dynamics of Western Flower Thrips (Thysanoptera: Thripidae) to Lettuce in the Salinas Valley of California?

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important, worldwide vector of two tospoviruses (Family Bunyaviridae; Genus Tospovirus), Impatiens necrotic spot virus (INSV) and Tomato spotted wilt virus (TSWV). In the Salinas Valley of California, INSV causes severe necrosis, stunting, and crop losses to lettuce (Lactuca sativa L.). Because broccoli (Brassica oleracea var. italica L.) and cauliflower (Brassica oleracea var. botrytis L.) are major rotation crops with lettuce in the Salinas Valley, it is critical to understand if these Brassicas influence the dispersal dynamics of F. occidentalis. In 2013 and 2014, surveys were conducted evaluating yellow sticky cards and plant samples in lettuce, broccoli, and cauliflower fields in three regions of the Salinas Valley. F. occidentalis were collected on sticky cards from April to November and on foliage in all three regions. Two-choice oviposition assays as well as no-choice and two-choice feeding assays were conducted where F. occidentalis adults were exposed to leaves of lettuce, broccoli, and cauliflower. A significantly greater number of eggs was found on lettuce than on broccoli or cauliflower leaves in the choice assay, whereas for the broccoli and cauliflower choice assay, the number of eggs retrieved was low and not significantly different between hosts. The number of F. occidentalis feeding spots and leaf area injury ratings were similar on broccoli and lettuce leaves but were significantly lower on cauliflower than on lettuce and broccoli leaves. The implications of these results on thrips and plant virus management are discussed.

Fast Recognition of Lecanicillium spp., and Its Virulence Against Frankliniella occidentalis.

BackgroundFrankliniella occidentalis (Thysanoptera: Thripidae) is a highly rasping-sucking pest of numerous crops. The entomogenous fungi of Lecanicillium spp. are important pathogens of insect pests, and some species have been developed as commercial biopesticides. To explore Lecanicillium spp. resources in the development of more effective F. occidentalis controls, efficient barcode combinations for strain identification were screened from internal transcribed spacers (ITS), SSU, LSU, TEF, RPB1, and RPB2 genes.ResultsSix genes were used to reconstruct Lecanicillium genus phylogeny. The results showed that ITS, TEF, RPB1, and RPB2 could be used to identify the strains. All phylogenetic trees reconstructed by free combination of these four genes exhibited almost the same topology. Bioassay studies of a purified conidial suspension further confirmed the infection of second-instar nymphs and adult female F. occidentalis by seven Lecanicillium strains. L. attenuatum strain GZUIFR-lun1405 was the most virulent, killing approximately 91.67% F. occidentalis adults and 76.67% nymphs after a 7-day exposure. L. attenuatum strain GZUIFR-lun1405 and L. cauligalbarum strain GZUIFR-ZHJ01 were selected to compare the fungal effects on the number of eggs laid by F. occidentalis. The number of F. occidentalis nymphs significantly decreased when F. occidentalis adults were treated with L. cauligalbarum strain GZUIFR-ZHJ01.ConclusionsThe combination of ITS and RPB1 could be used for fast recognition of Lecanicillium spp. This is the first report of the pathogenicity of L. attenuatum, L. cauligalbarum, L araneogenum, and L. aphanocladii against F. occidentalis. Additionally, L. cauligalbarum strain GZUIFR-ZHJ01 caused high F. occidentalis mortality and inhibited the fecundity of the pest.

Assessment of Chrysoperla comanche (Banks) and Chrysoperla externa (Hagen) as Biological Control Agents of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on Tomato (Solanum lycopersicum) under Glasshouse Conditions.

We tested the predatory capacity of newly-hatched or newly-molted Chrysoperla comanche (Banks) and Chrysoperla externa (Hagen) larvae after a 24 h fasting period on adults of Frankliniella occidentalis (Pergande) that were feeding on tomato plants (at vegetative and blooming stage) under glasshouse conditions. We also recorded fruit damage by the thrips. Both Chysoperla spp. depredated a similar number of F. occidentalis (thrips) adults regardless of the phenological stage of the plant. Second and third instar larvae of both species consumed significantly more thrips than first instar during plant blooming, however when the plant was at vegetative stage, all larval stages of both species predated a similar number of thrips. A significantly lower fruit damage percentage was recorded at the blooming plant when C. comanche larvae were in the experimental cage, however the presence of second and third instar of both species significantly reduced the fruit damage. No foliar damage was recorded. As far as we know, this is the first assessment of the predatory capacity of C. comanche and C. externa on thrips feeding on tomato under glasshouse conditions.

Overwintering of the western flower thrips in outdoor strawberry crops

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of semi-protected strawberry crops in the UK. These crops are grown outdoors but sheltered by clear polythene tunnels during the growing season from about April to October. The aims of the study were (1) to test whether F. occidentalis overwinters in strawberry crops in central England, where overwintering in outdoor crops has not previously been demonstrated and (2) to test whether overwintering affects the thrips population during the following season. F. occidentalis was found breeding on several crop weeds that often flower throughout the year, including common chickweed (Stellaria media), groundsel (Senecio vulgaris) and dandelion (Taraxacum officinale). F. occidentalis female adults were found throughout the winter in flowers of these weeds and caught every month on blue sticky traps. Transparent emergence traps placed over various locations in a second-year crop in March caught adult thrips over the following month, showing that thrips survived within the crop. Second-year strawberry crops had earlier infestations and significantly more F. occidentalis adults per flower than nearby first-year crops at the start of the season, indicating that thrips that overwinter in and around retained crops contribute to pest build-up in the following season. Control of overwintering F. occidentalis after the end of first-year cropping before second-year cropping, or growing crops for only 1 year, is a potential strategy to improve thrips management in strawberry. The survival of F. occidentalis over winter on outdoor crops raises concerns that the species could in time become established on other outdoor crops.

Sweet Corn, Explored as a Companion Plant, Mitigates Sucking Insects in Industrial Tomato Plants, Pre-flowering Stage

Plant diversification mitigates colonization by herbivorous insects in agricultural systems. Tomato and sweet corn generate raw material, for industrial processing, with outstanding production in Goiás state, Brazil. Yet, little is known about the potential of sweet corn as a companion plant for sucking insects, and natural enemies, in tomato plants. We collected pests and natural enemies in tomato (pre-flowering stage) plants under three treatments: isolated tomato plants (T1), tomato plants with sweet corn in the border (T2), and tomato plants with polyculture (garlic, lettuce, and squash) in the border (T3). The insects were collected by yellow sticky traps. Dalbulus maidis (29.52%), Frankliniella schultzei (23.90%), F. occidentalis (18.72%) and Myzus persicae (15.20%) corresponded to 87.34% of the total insects collected. Tomato plants cultivated with sweet corn on the border had lower infestation of the thrips, F. schultzei as well as the aphid M. persicae. The number of D. maidis and F. occidentalis adults did not change according to the treatments. Diabrotica speciosa and Astylus variegatus were more collected in tomato plants with adjacent sweet corn. Predators and parasitoids represented only 6.62% of the total abundance. Cycloneda sanguinea and parasitoids were more collected in tomato plants with polyculture (T3). Tomato with sweet corn or polyculture favored the abundance of the predator Sphaerophoria scripta. Considerations around the control of insect pests and the sustenance of natural enemies in tomato plants, with sweet corn acting as a companion plant, in the pre-flowering stage of that Solanaceae, are demonstrated.

Characterization of two novel heat shock protein 70s and their transcriptional expression patterns in response to thermal stress in adult of Frankliniella occidentalis (Thysanoptera: Thripidae)

Heat shock protein 70 (HSP70) is one of the most important members in the heat shock protein family, and plays important roles in the thermotolerance of insect. To explore the molecular mechanism of thermotolerance of Frankliniella occidentalis adults, the difference in the expression of HSP70s in F. occidentalis male or female adults under the thermal stress was studied under the laboratory conditions. Two full length cDNAs of HSP70s gene (Fohsc704 and Fohsc705) were cloned from F. occidentalis by using RT-PCR and RACE. The genomic sequence was demonstrated by genomic validation, and the position and size of the intron were analyzed by sequence analysis of cDNA. Real-time PCR was used to analyze the HSP70 expression patterns. The cDNA of Fohsc704 and Fohsc705 possessed 2 073 and 1 476 bp which encoded 690 and 491 amino acids (aa) with a calculated molecular weight of 75 and 54 kDa, respectively. Four introns in Fohsc704 and six introns in Fohsc705 protein were found. However, the HSP70 protein sequences in our study were ended with EKKN and GIFL, which were different from the reported FoHSP70s. Various expression patterns of Fohsc704 and Fohsc705 were found in both genders of F. occidentalis under thermal stress. The expression of Fohsc704 and Fohsc705 reached to the highest level at –12 and –8°C in male adults, respectively, and Fohsc705 expressed the highest level at 33°C in female adults. In conclusion, HSP70s of F. occidentalis in our study are novel heat shock proteins. There were difference in expression patterns of the two hsc70s in genders of F. occidentalis, and the two HSP70s play important roles in the thermotolerance of F. occidentalis.

Behavioral responses of Frankliniella occidentalis to floral volatiles combined with different background visual cues

The Western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), is one of the most destructive sucking pests of flowering plants. We examined behavioral responses of F. occidentalis adults to the floral volatiles of Rosa chinensis, Gardenia jasminoides, and Tagetes erecta in a Y-tube olfactometer with background visual cues (green, red, white, yellow, and blue backgrounds). The results show that F. occidentalis adults had similar responses under all the different background colors, but the responses by sex varied significantly when offered floral volatile or clean air. In pairings of floral volatiles, female F. occidentalis adults presented significant preferences (R. chinensis > G. jasminoides > T. erecta) in each treatment, while male F. occidentalis adults had no significant preference. Furthermore, the responses of female F. occidentalis adults to the three different floral volatiles compared with each other were greater under green and blue backgrounds than red, white, or yellow backgrounds. However, the responses of male F. occidentalis adults to floral volatiles were similar to all five backgrounds. These results indicate that female thrips could discriminate different floral volatiles, while male thrips could not. Both male and female thrips performed steady preferences of floral volatiles under all the five visual backgrounds, and the behavioral responses of female thrips to the floral volatiles could be enhanced under the green and blue backgrounds. These findings could hopefully aid in the development of effective trapping and monitoring strategies for this pest.

Effect of heat shock on the susceptibility of Frankliniella occidentalis (Thysanoptera: Thripidae) to insecticides

Currently, insecticides are considered as the primary approach for controlling western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). However, the heavy use of insecticides resulted in high insect resistance and serious environmental pollution. Given its characteristics of ease of operation and environmental friendliness, insect control using high temperature is receiving considerable renewed research interest. However, although the combination of insecticides and high temperature to control F. occidentalis has been studied before, few studies have focused on the short-term effect of such treatment. In a laboratory study, F. occidentalis adults and second-instar nymphs were exposed to 45°C for 2 h. Then, their susceptibility to acetamiprid, spinosad, methomyl, and beta-cypermethrin was tested after different periods of recovery time (2–36 h). Additionally, the specific activity of three detoxification enzymes (esterase, glutathione S-transferase, and cytochrome p450 (CYP) monooxygenase) of the treated insects was determined. The results indicated that the fluctuation of susceptibility to insecticides and detoxification enzyme activity during F. occidentalis recovery from heat shock are related. Furthermore, several recovery time points (2, 30, and 36 h) of significant susceptibility to four tested insecticides compared with the control were found during the treatment of adults that were heat-shocked. Recovery time points of higher susceptibility compared with the control depended on different insecticides during the second-instar nymph recovery from heat shock. Interestingly, the fluctuation of CYP monooxygenase activity exhibited a trend that was similar to the fluctuation of susceptibility to insecticides (especially spinosad) during the recovery from heat shock of adults. In addition, the glutathione S-transferase and CYP monooxygenase activity trend was similar to the trend of susceptibility to spinosad during the recovery from heat shock of second-instar nymphs. Our results provide a new approach for controlling F. occidentalis using the combined heat shock and insecticide. This effectively enhances the control efficiency of heat shock and significantly reduces the application of insecticides.

Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae): Evaluation of Potential Attraction to Vanilla Extract under Laboratory and Greenhouse Conditions

Plant-derived essential oils or extracts and their associated volatiles can serve as insect attractants to enhance adult captures when used as whole plants or extracts that are incorporated onto colored sticky traps. In our study, we initially assessed the attractiveness of western flower thrips (WFT) (Frankliniella occidentalis) adults to vanilla extract in the laboratory using choice and no-choice experiments by comparing one (0.05 mL) and two (0.10 mL) drops of vanilla extract (0.029% and 0.059%, respectively). In the choice experiments, a drop of water and drop of vanilla extract were placed on opposite sides of a petri dish. One WFT was placed in the center of the petri dish, and observations were made on whether there was preferential movement to the water or vanilla extract. For the no-choice experiments, one petri dish only contained a drop of water, whereas another petri dish only contained a drop of vanilla extract. One WFT was placed into each petri dish and movement was observed to assess whether the WFT moved toward the water or to the vanilla extract. We then determined if yellow sticky cards containing vanilla extract were more attractive to WFT adults than those with water, by using the number of adults captured on yellow sticky cards as an estimate under greenhouse conditions. Western flower thrips adults were not attracted to vanilla extract based on the results associated with the choice and no-choice tests conducted under laboratory conditions with no differences in selection between vanilla extract and water. In addition, there was no evidence that inoculating yellow sticky cards with vanilla extract enhanced the number of adults captured on yellow sticky cards. Overall, the use of vanilla extract in attracting WFT adults to yellow sticky cards is not justifiable under the parameters of our study.