Female Thrips Research Articles

Chemical Composition of Five Lamiaceae Essential Oils and Their Insecticidal and Phytotoxic Activity.

The Lamiaceae family is widely distributed worldwide. In this study, we investigated the insecticidal activity of five Lamiaceae essential oils against Thrips flavus Schrank and the phytotoxic activity against Glycine max (L.) Merr., Zea mays L., Portulaca oleracea L., and Echinochloa oryzoides (Ard.) Fritsch. Then, the chemical composition of the five essential oils was analyzed by using gas chromatography-mass spectrometry (GC-MS). The five Lamiaceae essential oils were melissa, basil, rosemary, negundo chastetree, and salvia. The main constituents of the five Lamiaceae essential oils were preliminarily determined to be as follows: α-pinene and 1,8-cineole in the rosemary essential oil; β-pinene, γ-terpinene, and d-limonene in the negundo chastetree essential oil; β-cadinene and isolongifolen-5-one in the melissa essential oil; 5-allylguaiacol in the basil essential oil; and isopropyl myristate, linalyl acetate, and linalool in the salvia essential oil. Using a bioassay, it was found that, among the five essential oils, the melissa essential oil exhibited the lowest LC50 value, which was 0.18 mg/mL, and the salvia essential oil exhibited the highest LC50 value, which was 0.42 mg/mL. The control efficacy of the five essential oils significantly increased with time and concentration in pot experiments. The negundo chastetree, basil, rosemary, and salvia essential oils at 900.00 g a.i.·hm-2 showed high control efficacy against T. flavus, with values higher than 90%. Female thrips were attracted to the negundo chastetree essential oil. The five essential oils were also tested for their effects on the germination rate, germination potential, germination index, and shoot length of G. max, Z. mays, P. oleracea, and E. oryzoides. The basil essential oil significantly inhibited the germination of P. oleracea, with germination at a concentration of 1.0 mg/mL being only 11.11 ± 5.09%. This study provides a reference for the development of botanical pesticides to control T. flavus, crops, and weeds.

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.

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

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

Differences between volatiles that affect the attraction of different Rosa chinensis (Rosales: Rosaceae) cultivars for Frankliniella intonsa (Thysanoptera: Thripidae)

AbstractFrankliniella intonsa Trybom is a common flower‐inhabiting thrips species and an economically important pest of numerous horticultural and agricultural crops. Olfactory cues are important for thrips to find host plants. In this study, the olfactory behavioral responses of F. intonsa to volatiles from five Rosa chinensis cultivars (Samantha, Zeprti, Queen Elizabeth, Golden Scepter, and Witte Koster) were tested in Y‐tube and six‐arm olfactometer experiments. Then the volatile components of the R. chinensis flowers were analyzed by SPME coupled with gas chromatography–mass spectrometry (GC–MS). Both female and male thrips showed significant preferences for volatiles from the five R. chinensis cultivars compared with clean air (CA). However, according to the six‐arm olfactometer bioassays, female F. intonsa adults were better than male thrips at recognizing the odor stimulation and showed the strongest olfactory preference for Samantha, followed by Zeprti, Queen Elizabeth, Golden Scepter, and then Witte Koster. SPME‐GC–MS analysis identified 56, 53, 53, 57, and 60 components in the volatile profiles of Samantha, Zeprti, Queen Elizabeth, Golden Scepter, and Witte Koster, respectively. Eugenol (12.53%) was the most abundant volatile compound in cultivar Witte Koster, ɑ‐pinene was the most abundant compound in Samantha (18.26%) and Zeprti (23.73%), and phenylethyl alcohol was the most abundant in Queen Elizabeth (30.10%) and Golden Scepter (31.33%). Therefore, the olfactory responses of F. intonsa to different R. chinensis cultivars demonstrated that host‐related volatiles play an important role in thrip host‐searching. Future mitigation approaches, for example, attractant traps, could still be used for key monitoring and control of this pest.

The Preference of Thrips tabaci for Allium cepa, Allium fistulosum, and Allium roylei

Thrips tabaci Lind. (Thysanoptera: Thripidae) is a key pest of onions worldwide. It causes both direct and indirect damage to onion crops, resulting in high yield losses. Today, the Integrated System of Production and Plant Protection requires onion growers to use onion- thrips-resistant cultivars. It has become apparent that the improvement of existing onion cultivars may not be a sufficient, so it is necessary to search for desirable plant traits related to disease and pest resistance among existing and wild cultivars. For this purpose, we conducted bioassays on the possible preference of T. tabaci for three different cultivars of Allium cepa L., namely, Alibaba, Bila, Tęcza, one cultivar Kroll of Welsh onion, Allium fistulosum L., and the wild species Allium roylei Stearn. The settling preference and the oviposition rate of female onion thrips were evaluated using choice and no-choice laboratory tests, respectively. During the bioassay, on leaf sections of the A. roylei species, a significantly higher number of T. tabaci females was recorded compared to the cv. Tęcza of the A. cepa species and the cv. Kroll of the A. fistulosum species in each observation period. Significantly more thrips settled on cv. Kroll compared to Alibaba and Bila. Regarding the results obtained on A. cepa, significantly fewer females were found on cv. Bila compared to cv. Tęcza. Opposite results were observed in a combination of cvs. Tęcza–Alibaba, where significantly more insects settled on the leaves of cv. Alibaba. Statistically significant differences between cultivars/species were found in the number of hatched larvae on the leaves of the tested cultivars/species of onion. The lowest number of larvae hatched from eggs laid on A. roylei, as compared to A. fistulosum and the cultivars of A. cepa, except for Bila.

Eff ect of volatile organic compounds of entomopathogenic fungi of the genus Lecanicillium and their component, the acetic acid, on the female behaviour of the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae)

The e ect of VOCs of six entomopathogenic fungal strains from genus Lecanicillium on the behavioral responses of the western ower thrips females Frankliniella occidentalis on vegetative bean plants and in a Y-shaped olfactometer was studied. The signi cant repellent reactions of thrips females and a decrease in a number of o spring by 33-34% were revealed after treatment the beans by conidial suspensions of L. lecanii strains F2 and Vl 29 in the concentration of 1 × 107 spores/ml. Strains Vl 21 ( L. muscarium ) and Vit 71 ( L. attenuatum ), which showed a repellent tendency towards thrips females, also caused a signi cant decrease of o spring number. The strains isolated from aphids (ARSEF 2332 of L. dimorphum and Vl 13 of L. longisporum ) showed a tendency towards attractiveness. In the Y-shaped olfactometer the repellency of the F2 strain and the attractiveness of the ARSEF 2332 strain were con rmed. The in uence of the other studied strains on the thrips behavioral reactions was unreliable. Acetic acid, tested in the olfactometer at doses corresponding to its content in the fungal VOCs over growing mycelium, caused di erent reactions of thrips females depending on the acid concentration: attractive reactions at the dose of 0.17 ppm; neutral - at the dose of 0.34 ppm; and weak repellent - at 0.85 ppm. The obtained data indicate that acetic acid, contained in the fungal VOCs, e ect on the behavioral responses of thrips females. The repellant e ect of the fungal spores of the genus Lecanicillium on thrips females and the negative impact on o spring number increase the e ectiveness of entomopathogenic fungi.

Effect of Sulfur Dioxide as a Component of the Volatile Organic Compounds of Fungi of the Genus <i>Lecanicillium</i> on the Phytophagous Western Flower Thrips and Peach Aphid

Earlier, using the MS7-200 quadrupole mass spectrometer developed by the IAP RAS, sulfur dioxide was detected as part of volatile organic compounds (VoCs) released into the air by entomopathogenic fungi (EPF) of the genus Lecanicillium. In this work, we evaluated the effect of this compound on such dangerous phytophages as the Western flower thrips Frankliniella occidentalis and the peach aphid Myzus persicae in low doses corresponding to the content of sulfur dioxide in the composition of VOCs over the growing mycelium of fungi. It was found that sulfur dioxide did not have a negative effect on female thrips F. occidentalis and their fertility when sulfur dioxide is injected into vials at concentrations of 9 and 17 ppm and kept for 2 hours. At a dose of 33 ppm, sulfur dioxide caused a 10% mortality of female thrips after 2 hours and 15.4% after 1 day, while a 36% decrease in female fertility was observed. Sulfur dioxide at concentrations of 17-33 ppm was nontoxic for peach aphid females after 2 hours. Aphid mortality at the level of 26% was noted after 2 days at a sulfur dioxide concentration of 33 ppm, while fertility decreased by 22%. At a dose of 23 ppm, sulfur dioxide reduced the fertility of aphids most significantly - by 30%. The data obtained indicate the influence of sulfur dioxide contained in the composition of fungal VOCs on the behavioral reactions of phytophages.

Transcriptome analysis of female western flower thrips, Frankliniella occidentalis, exhibiting neo-panoistic ovarian development.

The western flower thrips, Frankliniella occidentalis, is one of the most devastating insect pests with explosive reproductive potential. However, its reproductive physiological processes are not well understood. This study reports the ovarian development and associated transcriptomes of F. occidentalis. Each ovary consisted of four ovarioles, each of which contained a maximum of nine follicles in the vitellarium. The germarium consisted of several dividing cells forming a germ cell cluster, presumably consisting of oocytes and nurse cells. The nurse cells were restricted to the germarium while the subsequent follicles did not possess nurse cells or a nutritive cord, supporting the neo-panoistic ovariole usually found in thysanopteran insects. Oocyte development was completed 72 h after adult emergence (AAE). Transcriptome analysis was performed at mid (36 h AAE) and late (60 h AAE) ovarian developmental stages using RNA sequencing (RNASeq) technology. More than 120 million reads per replication were matched to ≈ 15,000 F. occidentalis genes. Almost 500 genes were differentially expressed at each of the mid and late ovarian developmental stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that these differentially expressed genes (DEGs) were associated with metabolic pathways along with protein and nucleic acid biosynthesis. In both ovarian developmental stages, vitellogenin, mucin, and chorion genes were highly (> 8-fold) expressed. Endocrine signals associated with ovarian development were further investigated from the DEGs. Insulin and juvenile hormone signals were upregulated only at 36 h AAE, whereas the ecdysteroid signal was highly maintained at 60 h AAE. This study reports the transcriptome associated with the ovarian development of F. occidentalis, which possesses a neo-panoistic ovariole.

The Effect of Species Soybean Vein Necrosis Orthotospovirus (SVNV) on Life Table Parameters of Its Vector, Soybean Thrips (Neohydatothrips variabilis Thysanoptera: Thripidae).

Simple SummarySoybean vein necrosis, caused by soybean vein necrosis virus (SVNV) is an important viral disease of soybeans that can be seed borne or insect vectored. This plant viral disease affects seed qualitative parameters, including seed oil content. Increased damage is observed in late planted soybeans. The disease is widespread, and almost all soybean-growing states in USA are affected. Globally, SVNV is reported in Canada, the United States, Egypt and Pakistan. In order to manage the disease, it is important to understand the vector’s biology and the effect of SVNV on life table parameters (survival, longevity, mortality, doubling time, generation, rate of intrinsic increase) of vector soybean thrips, which can help to establish pest management predictive models. We used an age-stage two-sex life table estimation model to define the effect of SVNV on the life parameters of male and female soybean thrips. Overall, we found that SVNV infection increased viruliferous thrips survival, longevity, gross reproduction rate, life expectancy and decreased population doubling time. Overall viruliferous thrips benefit from SVNV infection and transmission due to better survival, longevity and increased fitness.Soybean vein necrosis orthotospovirus (SVNV: Tospoviridae: Orthotospovirus), the causal agent of soybean vein necrosis disease, is vectored by soybean thrips Neohydatothrips variabilis (Beach, 1896), and to a lesser extent by five other thrips species. There is increasing incidence of soybean vein necrosis (SVN) disease in all soybean growing states in the United States, Canada, Egypt and Pakistan, necessitating a study of the system’s ecology and management. We addressed the effect of SVNV on the life table parameters of the vector. We used an ‘age-stage two-sex’ life table approach, which provided detailed life stage durations of each larval instar and adults (both sexes). Our results showed that the intrinsic rate of increase (r), finite rate of increase (λ) and mortality index (qx) were higher in the infected population, while the net reproduction rate (Ro), cumulative probability of survival (lx) and gross reproduction rate (GRR) were lower in the uninfected population. Overall, in both infected and uninfected populations, the number of eggs producing haploid males via arrhenotoky ranged from 9–12 per female. Male to female ratio was female biased in the infected population. Overall, our study provided evidence that virus infection, by decreasing the population doubling time, could enhance the virus and vector populations in soybeans.

Morphology of the Female Reproductive System of the Soybean Thrips, Neohydatothrips variabilis (Beach, 1896) (Thysanoptera: Thripidae).

Simple SummarySoybean thrips are an important vector of Soybean vein necrosis virus disease, found in all soybean-growing regions of the United States and Canada. The disease reduces the seed oil content and fatty acid profiles in infected plants. It is important to know the morphology of the female reproductive system of soybean thrips to understand the egg-laying mechanism and develop strategies for virus vector management. For this purpose, we used fuchsin staining, paraffin-based histology, dissections, serial block-face scanning electron microscopy and confocal laser scanning microscopy techniques to understand the structure and motorization of the internal and external genitalia of soybean thrips. We also investigated the egg-laying behavior of soybean thrips. The female reproductive system is composed of two ovaries, an oviduct, an accessory gland, an appendage gland, a common oviduct and a vagina. Female soybean thrips lay eggs in the parenchymatous tissues near the veins of the leaves. The appendage gland likely secretes lubrication to facilitate the movement of eggs through the external genitalia. Seven muscles support the movement of eggs from the ovaries to the leaf surface. The anatomy and probable role of each muscle is also described.Soybean thrips (Neohydatothrips variabilis) are an important phytophagous vector of the widely recognized Soybean vein necrosis orthotospovirus (SVNV). Understanding the egg-laying behavior of these thrips could aid in developing strategies for the management of the vector and virus. In this study, we described the egg-laying behavior of N. variabilis and reconstructed the three-dimensional morphology of the female terminalia by using serial block-face scanning electron microscopy (SBFSEM) and confocal laser scanning microscopy (CLSM). The female reproductive system consists of two panoistic ovaries consisting of eight ovarioles. The appendage gland is connected to the ovaries by two muscles, and to the body wall by a single muscle. The spermatheca is connected to the eighth tergum through four branched muscles, to the basivalvulae of the ovipositor by one muscle and to the vagina by a single muscle. The external genitalia are operated by seven muscles. The movement of the eggs inside the ovipositor is achieved by the back and forth “rocking” movement of the first valvulae and valvifer. Eggs are deposited into the parenchymatous tissue alongside leaf veins. To the best of our knowledge, this is the first study describing the internal and external genitalia of N. variabilis.

Effect of cold storage on development and demographic parameters of Scolothrips longicornis fed on two-spotted spider mite.

Cold storage effects on the female predatory thrips Scolothrips longicornis Priesner (Thysanoptera: Thripidae) fed on Tetranychus urticae Koch eggs for different time periods (5, 10, 20 and, 30 days) at 5 or 25 °C (control) on development and life table parameters were examined. Female adult duration and female total longevity were not influenced by the period of cold storage. The minimum mean female total longevity (28.1 ± 0.32 day) was observed in the 30-day treatment. The oviposition period decreased with increasing cold storage duration. All life table parameters of S. longicornis demonstrated a significant difference across treatments. Our results demonstrated that the female adult of S. longicornis could be maintained at 5 °C for 5-days with minimal reduction in the life-history process. This would be beneficial in the storage and mass production of S. longicornis in biocontrol programs involving T. urticae.

Molecular Characterization and Assessment of Abundance of Thrips hawaiiensis (Morgan, 1913) on Three Plantations of Cavendish Banana in Davao del Norte, Philippines

The study aimed to verify the identity of Thrips hawaiiensis (Morgan, 1913) (Thripidae: Thysanoptera) based on mitochondrial cytochrome C oxidase I marker and determine its seasonal abundance on Gran Naine, Tall Williams, and GCTCV-218 Cavendish banana plantations in Panabo City, B.E. Dujali, and Carmen in Davao del Norte, Philippines. Fifteen (15) flowering/fruiting plants per cultivar per plantation were selected. The survey was conducted on 11–29 Aug 2020, 14–26 Nov 2020, 08–18 Mar 2021, and 11–25 May 2021. Thrips were sampled from bunches consisting of flowers and fruits by the shaking/tapping method. Temperature and rainfall data were obtained from PAGASA. All thrips samples had a significant match with T. hawaiiensis (GenBank KX233567.1) having 100% query cover with 99.39–99.70% nucleotide identity. Female thrips were dominant on all Cavendish cultivars and in the dry season, their counts doubled, whereas male thrips counts increased more than five times. Analysis of variance between the mean numbers of thrips showed no significant difference among cultivars during the dry and wet seasons (p < 0.05). There was a significant difference between mean counts of female and first instar larvae but no significant difference between the mean counts of female, male, and second instar larvae in Panabo City; whereas in B. E. Dujali, and Carmen, there was a significant difference between the mean numbers of female, male, and first and second instar larvae but no significant difference between the mean numbers of male and first and second instar larvae (p < 0.05). Regression analysis showed that thrips abundance was slightly affected positively by maximum average temperature and seemingly not affected by rainfall.

Life History of Thrips hawaiiensis (Morgan) Reared on Flower of “Saba” Banana (Musa acuminata x balbisiana Colla)

Thrips hawaiiensis (Morgan) is a pest of banana, mango, and pomelo. The study aimed to determine the development and reproductive capacity of thrips under laboratory condition. To start the culture, female thrips were collected from Beltran “Saba” banana plantation in Tuao, Cagayan, Philippines. Thrips were reared on fresh banana flowers in glass containers covered with cotton gauze pad sealed with rubber bands at temperatures of 25 ± 1.0 to 32 ± 2.0 °C, relative humidity of 78–99%, and photoperiod of 12:12 h (L:D). Forty (40) eggs laid within 8 h by first-generation female were observed from 05 Oct–16 Nov 2020. Three (7.5%) males and 37 (92.5%) females emerged from unfertilized eggs. Male average egg incubation, first instar, and second instar larval, prepupal, and pupal days were 1.33 ± 0.47, 1.33 ± 0.47, 1.33 ± 0.47, 1.00 ± 0.00, and 1.33 ± 0.47, respectively. Male average total development period and lifespan were 8.67 ± 0.62 and 9.33 ± 0.94, respectively. Female average egg incubation, first instar larva, second instar larva, prepupa, and pupal periods were 1.24 ± 0.43, 1.24 ± 0.43, 2.38 ± 0.48, 0.59 ± 0.20, and 2.38 ± 0.48, respectively. Female average total development period from egg to adult emergence and lifespan from egg to post oviposition until the adults are dead were 8.89 ± 0.52 and 23.19 ± 7.07, respectively. Female average pre-oviposition, oviposition, and post-oviposition periods were 1.05 ± 0.38, 12.27 ± 6.69, and 0.95 ± 1.20, respectively. The average number of eggs laid by each female was 196.92 ± 75.70. Female second instar larva and pupa development period were longer – which could be due to the bigger body size – and the average lifespan was twice as long as that of male. T. hawaiiensis is a short-lived, asexual insect with high fecundity; based on the life span of female thrips studied, between 7–8 thrips generations could be developed annually.

Thrips (Insecta: Thysanoptera) Species Infesting Garlic (Batanes Red) in Selected Farms in Batanes, Philippines

The study aimed to determine the species of thrips infesting garlic (Batanes Red) in the Department of Agriculture–Batanes Experiment Station (DA-BES) in Ihubok 1, Basco; DA-BES Dibtung, Radiwan, Ivana; and in the Calderon Farm in Radiwan, Ivana, Batanes. Sampling was done in February 2020. A total of 950 adult female thrips were collected from all study sites. The majority of the thrips were collected from DA-BES Farm in Ihubok 1, Basco with 89.89%, followed by the Calderon Farm in Ridawan, Ivana with 5.16%, and DA-BES Farm in Dibtung, Ridawan, Ivana with 4.95%. Thrips were represented by two terebrantian species, namely: Thrips tabaci Lindeman (Thripidae) with 97.37%, Anaphothrips sudanensis Trybom (Thripidae) with 2.32%, and a tubuliferan species Haplothrips gowdeyi (Franklin) (Phlaeothripidae) with 0.31%. T. tabaci was the dominant species in all study sites. A. sudanensis was found in all the study sites but in low number, while H. gowdeyi was present in two DA-BES study sites but absent in the Calderon Farm. This is the first report of A. sudanensis and H. gowdeyi infesting garlic in the Philippines.

Field Biology of Scolothrips sexmaculatus (Thysanoptera: Thripidae) as a Predator of Tetranychus pacificus (Acari: Tetranychidae) in California Almonds.

Biological control of tetranychid spider mites in California almonds has predominantly been associated with predatory mites in the family Phytoseiidae. However, changes in production practices, including shifts to more sustainable chemical control programs, have resulted in a trophic shift leading to the predominance of six-spotted thrips, Scolothrips sexmaculatus Pergande, as the primary mite predator. Over a 3-yr period, we studied S. sexmaculatus biology and relationship to Tetranychus pacificus McGregor in almond orchards in the southern San Joaquin Valley of California. Scolothrips sexmaculatus had two periods of activity in response to increases in T. pacificus density, one in the spring and one in the summer. Sex ratios were consistently skewed to more than 90% females captured on yellow sticky traps, with females producing eggs from May to October. Female thrips were larger than males, and both sexes were larger from June to September when temperatures were warmer and food was more abundant. In response to spider mite outbreaks, S. sexmaculatus increased from approximately 2/trap/wk to an average of 1,272/trap/wk over a 5-wk period, representing a population doubling time of 4.0 d. Over this time, we described trends in T. pacificus and S. sexmaculatus density that are consistent with population regulation through predator-prey relationships by a specialist predator.

Crowding leads to higher incidence of brachypterous females in the tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae)

• In wing-polyphenic insects, crowding generally promotes to macropter production. • Female of F. fusca exhibits wing diphenism governed by environmental conditions . • Effect of larval density on wing form determination was detected by rearing trials. • Percentage of female macropters decreased as larval density increased. • Developmental time and body length did not differ between two wing morphs. The effects of larval density on the wing form determination of female tobacco thrips, Frankliniella fusca , were investigated by rearing thrips on leaf disks at 27.5 °C. The developmental period, head width, body length, and forewing length of individuals in each wing morph were determined to assess the relationships among larval density, growth, and wing form. Data showed that higher rearing densities increased the production of female F . fusca brachypters. There was no consistent difference in the mean developmental periods between the two wing morphs or among all 5 density treatments. The body length of females tended to decrease with increasing rearing density, but there was no significant difference in body size between the two wing morphs when they were reared under the same density level.

First Record of Fungi Isolated from Thrips tabaci Lindeman on Garlic (Ilocos White) in Batac, Philippines

The study aimed to isolate, and identify fungi associated with live adult female Thrips tabaci Lindeman (Thysanoptera: Thripidae) from garlic (Ilocos White) in Tubug Experimental Area of Mariano Marcos State University in Batac, Ilocos Norte, Philippines. Thrips were collected randomly from garlic (Ilocos White) plants within 200 m2 area in one garlic field of about 400 m2 using the tapping/beating method. Thrips were sorted and examined under the microscope. For the isolation of fungi, 20 live adult female thrips were selected from the collection consisting of females and larvae. Standard isolation of fungi from thrips was conducted and pure cultures of fungal isolates were maintained on PDA (potato dextrose agar) slants. Fungal isolates were processed for DNA extraction, PCR (polymerase chain reaction) amplification, and gel electrophoresis. Forward and reverse reads were paired to generate a consensus sequence, which was used in the Basic Local Alignment Search Tool (BLAST) queries to determine taxonomic identity. Out of the 10 fungal isolates, nine were identified as Fusarium proliferatum while one is Aspergillus candidus based on ITS (internal transcribed spacer) gene sequence. They both belong to Class Ascomycota. F. proliferatum on PDA shows varying characteristics of its mycelial growth from being scanty to fluffy, off-white to light yellow, brown, or purple while A. candidatus exhibits the entire margin and bluish-green pigmentation with a fertile layer composed of catenate conidia formed from the vesicle of the conidiophore. F. proliferatum was dominant among the isolates. The manner of isolating them from Thrips tabaci proved that they are endophytes living within them, and these are new records in the Philippines.

Effects of melon yellow spot orthotospovirus infection on the preference and developmental traits of melon thrips, Thrips palmi, in cucumber.

Melon yellow spot orthotospovirus (MYSV), a member of the genus Orthotospovirus, is an important virus in cucurbits. Thrips palmi is considered the most serious pest of cucurbits because it directly damages and indirectly transmits MYSV to the plant. The effects of MYSV-infected plants on the development time, fecundity, and preference of the thrips were analyzed in this study. Our results showed that the development time of male and female thrips did not differ significantly between MYSV-infected and non-infected cucumbers. The survival rate of thrips in non-infected and MYSV-infected cucumbers were not significantly different. In a non-choice assay, T. palmi adults were released on non-infected and MYSV-infected cucumbers and allowed to lay eggs. The number of hatched larvae did not significantly differ between non-infected and MYSV-infected cucumbers. In a choice assay, MYSV had no detectable effect on the number of adult thrips and preceding hatched larvae. In a pull assay, the settling rate of thrips on the released plant did not differ significantly when the adult thrips were released to non-infected or MYSV infected cucumbers for any cucumber cultivar. Based on our results, we propose that the effects of MYSV-infected cucumbers on the development time, fecundity, or preference of T. palmi may not be an important factor in MYSV spread between cucumbers.

Novel mechanism of thrips suppression by Cry51Aa2.834_16 Bt toxin expressed in cotton

Genetically engineered (GE) crops that express insecticidal traits have improved the sustainability of insect pest management worldwide, but many important pest orders are not controlled by commercially available toxins. Development of the first transgenic thysanopteran- and hemipteran-active Bacillus thuringiensis (Bt) Cry51Aa2.834_16 toxin expressed in MON 88702 cotton will significantly expand the diversity of pests controlled in the crop. Here, we examined MON 88702 cotton activity against two thrips species within the same genera, Frankliniella fusca and Frankliniella occidentalis. We used a multi-component cotton tissue assay approach to understand effects on adult longevity, fecundity, and larval development. We found that in no-choice assays, cotton plants expressing MON 88702 suppress oviposition, when compared to a non-Bt cotton. MON 88702 did not kill a large proportion of F. fusca larvae or adults but killed most F. occidentalis larvae. Time series experiments with F. occidentalis larvae documented significant developmental lags for MON 88702 exposed individuals. We also found that female thrips preferred to oviposit on non-Bt cotton when provided a choice. Together these results describe the activity of MON 88702 against thrips. They document clear differences in toxin performance between different thrips species and throughout the insects' life cycle. Most importantly, we show that MON 88702 was associated with reduced oviposition via behavioral avoidance to the toxin. This is a novel mechanism of action for pest control for a Bt crop plant. Together, these results provide a basis to describe the mechanism of population control for MON 88702 cotton. © 2019 Society of Chemical Industry.

Repellent activity of Cymbopogon citratus and Tagetes minuta and their specific volatiles against Megalurothrips sjostedti

AbstractCowpea is an important source of protein for people in Africa. However, the crop suffers major damage and yield losses due to bean flower thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae). Although companion plants are known to reduce the damage caused by insect pests, the role of their volatiles in repelling pests from target plants has been the subject of few investigations. Here, we used the Y‐tube olfactometer experiments and chemical analyses to investigate the effect of volatiles from cowpea flowers and two companion plants; lemongrass, Cymbopogon citratus and Mexican marigold, Tagetes minuta on the olfactory responses of M. sjostedti. The results revealed that M. sjostedti males and females were repelled by the volatiles from freshly cut leaves of C. citratus. The combination of freshly cut leaves of C. citratus and cowpea flower was repellent to females but not to males. The female thrips, but not males, were repelled by the volatiles from the vegetative stage of T. minuta. Fifty‐four compounds were identified in the volatiles from two herbal plants. Among the major compounds, citral and a 4‐component blend comprised of dihydrotagetone, (Z)‐3‐hexenyl acetate, limonene and (Z)‐β‐ocimene repelled females but dihydrotagetone alone attracted females. While myrcene combined with cowpea flower volatiles enhanced the attraction of females M. sjostedti, when tested alone was not attractive. These results highlight the potential of volatiles from C. citratus and T. minuta to repel M. sjostedti females. The use of these plants as companion plants in a cowpea cropping system could reduce M. sjostedti infestation.