Thrips Larvae Research Articles

Microinjection-enabled gene silencing in first instar larvae of western flower thrips, Frankliniella occidentalis, reveals vital genes for larval survival.

The western flower thrips (Frankliniella occidentalis) is a significant agricultural pest, causing severe global yield losses due to extensive feeding damage and the transmission of plant pathogenic viruses. Despite recent advancements in RNA interference (RNAi) in thrips species, its application has been mostly limited to the adult stage. Given the crucial role of first instar larval thrips in acquiring and transmitting orthotospoviruses, achieving gene silencing in these larvae is critical for studying virus entry and acquisition. While thoracic and abdominal injections have proven effective in adult thrips, the low post-injection survival rate hinders their use in larval thrips. This study addresses this challenge by presenting a microinjection methodology to deliver dsRNA into the hemolymph of first instar larval thrips through the coxa, the first proximal segment of the foreleg. This method significantly improved larval survival rate by preventing detrimental damage to the internal tissues. Significant knockdown of V-ATPase-B, cytochrome P450 (CYP3653A2), and apolipophorin-II/I (ApoLp-II/I) transcripts was confirmed after 48 and/or 72 h post injection (hpi), corresponding to the first and second instar larval stages, respectively. Silencing CYP3653A2 or ApoLp-II/I significantly increased larval mortality. These findings demonstrate proof-of-principle of gene silencing and associated silencing phenotype (mortality) for first instar larval thrips and highlight the essential role of CYP3653A2 and ApoLp-II/I in larval vitality. Our RNAi-based tool offers an opportunity to investigate the molecular mechanisms of thrips-orthotospovirus interactions, as the virus must be acquired by young larval thrips for successful transmission to plants, thus presenting potential targets for thrips pest management.

Functional Response of Four Phytoseiid Mites to Eggs and First-Instar Larvae of Western Flower Thrips, Frankliniella occidentalis.

The predation capacity and functional responses of adult females of the phytoseiid mites Amblyseius largoensis (Muma), Proprioseiopsis lenis (Corpuz and Rimando), Paraphytoseius cracentis (Corpuz and Rimando), and Amblyseius swirskii (Athias-Henriot) were studied on eggs and first instars of the western flower thrips, Frankliniella occidentalis (Pergande), in the laboratory at 25 °C and 30 °C. At both temperatures, the functional response of all four phytoseiid mites was type II to first instars of the thrips. In contrast, when offered thrips eggs, the functional response was type III. At both temperatures tested, A. swirskii had the highest mean daily consumption of first-instar F. occidentalis, followed by A. largoensis, P. cracentis, and P. lenis. Amblyseius largoensis had the shortest handling time and the highest maximum attack rate when first-instar thrips were the prey. When fed on thrips eggs, A. largoensis had the highest mean daily consumption, followed by A. swirskii, P. cracentis, and P. lenis. On thrips eggs, A. swirskii showed the shortest handling time and highest maximum attack rate. Our findings indicate that all four phytoseiids had a better ability to prey on first-instar larvae of F. occidentalis compared to thrips eggs. At 25 and 30 °C, A. largoensis was the better predator on thrips larvae, whereas A. swirskii was superior in consuming eggs of F. occidentalis. Proprioseiopsis lenis was the inferior predator on both thrips larvae and eggs compared to the other phytoseiids tested.

A Recent Study on Various Arthropod Pests from Aquatic Plant Farms of West Bengal, India

The numbers of aquatic ornamental plant growers and hobbyists in India are increasing because of the introduction of new hybrid lotus (Nelumbo sp) and waterlilies (Nymphaea sp) mainly from South East Asian countries.Many insect pests are damaging different parts of the plants which are also causing economic loss.Among them the larvae of Leaf cutter moth (Elophilaobliteralis), thrips (Thrips flavus, T. tabaci), spider mites (Oligonychus spp. and Tetranychus spp.), caterpillarsare common and tough to eradicate from the aquascapes and the nursery pools of the aquatic farms.

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.

Evaluation of fumigant toxicity of cyclohexanone to 5 species of insect pests.

Cyclohexanone is a major precursor for nylon production and is also used as a pesticide solvent. In this study, cyclohexanone was evaluated as a fumigant against rice weevil adults, confused flour beetle adults, western flower thrips larvae and adults, spotted wing drosophila adults, and subterranean termite workers. Cyclohexanone fumigation was effective against all 5 insects, and there were considerable variations in susceptibility to cyclohexanone fumigation among the 5 species. At 20 °C, complete control of spotted wing drosophila adults was achieved in 1-h fumigation with 25 μl/l of cyclohexanone and complete control of eastern subterranean termite workers was achieved in 3-h fumigations with 50 μl/l dose of cyclohexanone. Stored-product insects confused flour beetle, and rice weevil adults were more tolerant to cyclohexanone fumigation. Fumigations of 24 h with 75 μl/l dose of cyclohexanone caused 100% mortality of rice weevil adults and 98% mortality of confused flower beetle adults. Even at a 100 μl/l dose, the 24-h fumigations did not achieve 100% mortality of confused flour beetle adults. At 5 °C, complete control of western flower thrips was achieved in 3- and 6-h fumigations with 100 and 50 μl/l doses of cyclohexanone, respectively. Cyclohexanone vapor concentrations were measured using cyclohexanone detector tubes. Vapor concentrations were far below the expected saturation concentration indicating that most cyclohexanone did not exist as vapor in fumigation chambers. The results of effective control of all 5 insect species suggest that cyclohexanone has the potential to be used as a fumigant for postharvest pest control.

Efficacy of Conventional and Biorational Insecticides against the Invasive Pest Thrips parvispinus (Thysanoptera: Thripidae) under Containment Conditions.

In 2020, the invasive Thrips parvispinus (Karny) was first detected in Florida, United States. In response to the implemented regulatory restrictions, we conducted laboratory experiments under containment conditions. Thrips larvae and adults were exposed to 32 products (conventional and biorational insecticides) either directly or indirectly. Direct exposure was performed using a Spray Potter Tower, while indirect exposure was conducted by evaluating residue toxicity against the thrips. Water served as a control. We assessed mortality and leaf-feeding damage 48 h post-treatment. Among the conventional insecticides, chlorfenapyr, sulfoxaflor-spinetoram, and spinosad caused high mortality across all stages in both direct and residue toxicity assays. Pyridalyl, acetamiprid, tolfenpyrad, cyclaniliprole-flonicamid, acephate, novaluron, abamectin, cyantraniliprole, imidacloprid, cyclaniliprole, spirotetramat, and carbaryl displayed moderate toxicity, affecting at least two stages in either exposure route. Additionally, chlorfenapyr, spinosad, sulfoxaflor-spinetoram, pyridalyl, acetamiprid, cyclaniliprole, cyclaniliprole-flonicamid, abamectin, and acephate inhibited larvae and adult's leaf-feeding damage in both direct and residue toxicity assays. Regarding biorational insecticides, mineral oil (3%) and sesame oil caused the highest mortality and lowest leaf-feeding damage. Greenhouse evaluations of spinosad, chlorfenapyr, sulfoxaflor-spinetoram, and pyridalyl are recommended. Also, a rotation program incorporating these products, while considering different modes of action, is advised for ornamental growers to avoid resistance and to comply with regulations.

Predator-prey interactions: How thrips avoid predation

Biological pest control is successful in many agricultural systems, yet various pests can still not be controlled with natural enemies. Examples are invasive thrips species such as Echinothrips americanus Morgan and Thrips parvispinus (Karny) in Europe. The lack of biological control of these pests in several crops has been subscribed to their complex life cycle and cryptic behaviours, but their antipredator behaviours may prevent successful control and have not been studied extensively. One of these behaviours is the potential of thrips to kill the eggs of predatory mites, which we quantified. Furthermore, we observed the behaviour of first- and second-instar thrips larvae when attacked by starved predatory mites Amblyseius swirskii Athias-Henriot. For comparison, we included Frankliniella occidentalis (Pergande), which shows an array of defensive behaviours, but can be controlled successfully by several species of predatory mites. Second-instar larvae and adults of F. occidentalis and T. parvispinus killed predator eggs, but E. americanus did not. First- and second-instar larvae of all three species swung their abdomen to defend themselves, and F. occidentalis and T. parvispinus produced anal droplets, which are also involved in defence. Predators were not successful in attacking any second-instar larvae during 15-minute observations, which is sufficiently long for an attack. First-instar larvae of F. occidentalis and T. parvispinus were sometimes successfully attacked by the predatory mite before they could mount a defence, but first-instar E. americanus always defended themselves and were almost never preyed upon. Cooling thrips larvae to suppress antipredator behaviour increased predation for all species and stages, except for first instars of F. occidentalis. In conclusion, the lack of successful control of E. americanus is not caused by killing predator eggs, but by the efficient defensive behaviour of both larval instars. Our study furthermore suggests that T. parvispinus can potentially be controlled by A. swirskii.

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.

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.

Efficacy of entomopathogenic fungi, nematodes and spinetoram combinations for integrated management of Thrips tabaci.

Two consecutive field trials using a blend of entomopathogens in combination with a new chemistry insecticide were conducted to determine treatment effects on onion thrips (Thrips tabaci Lindeman) populations, crop damage, plant development, crop yield and impact on natural enemies. Products were tested in an onion cropping system and included the insect pathogenic fungus Beauveria bassiana (isolate WG-11), an entomopathogenic nematode Heterorhabditis bacteriophora (strain VS) and the new-chemistry chemical insecticide spinetoram. In all treatments, a significant decrease in thrips per plant population was detected in both trials. Overall, dual application of entomopathogens and insecticide was more effective than singly applied treatments. The lowest number of thrips larvae (1.96 and 3.85) and adults (0.00 and 0.00) were recorded when treated with dual application of B. bassiana and spinetoram at 7 days post application (DPA) after the second spray application in 2017and 2018, respectively. Damage on onion plants was considerably decreased in all treatments relative to the control. The lowest damage was observed on onion plants treated with B. bassiana + spinetoram at 7 DPA after the second spray application during both years. A significant decrease in the number of natural enemies (beetles, spiders, mites, lacewings, ants and bugs) on onion plants was recorded during both years. Insect pathogens when applied alone and in combination with each other considerably protected arthropod natural enemies compared to insecticide application applied alone. Significant increase in plant agronomic traits was observed compared to the control. Among all the treatments, B. bassiana + spinetoram produced maximum leaf length, leaf weight, total leaves, neck diameter, bulb diameter, number of rings per bulb, bulb weight, dry matter and plant yield following the 2017and 2018 applications, respectively. The findings of the study reveal the potential of using insect pathogens and insecticide for control of T. tabaci. However, combinations containing spinetoram are harmful to nontarget organisms, whereas biological control agents help in protecting biodiversity in onion agroecosystems. © 2023 Society of Chemical Industry.

The Brazilian peppertree biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) displays a flexible feeding strategy between foliage and reproductive tissues

The biological control agent, Pseudophilothrips ichini, is being released for control of Brazilian peppertree, Schinus terebinthifolia (Anacardiaceae), an invasive weed of natural and agricultural areas of California, Florida, Hawaii, and Texas (USA). The thrips larvae and adults feed on flushed leaves and stems that are produced during the vegetative season of the host. However, during the reproductive season from September to December in Florida, few flushing leaves are available as resources are shunted to plant reproduction. As field releases were being implemented, thrips were found feeding and damaging immature fruits and flowers of their host. We hypothesized that the thrips used volatile organic compounds produced by reproductive tissues to locate and feed on these tissues. When examined under laboratory choice tests, individual thrips or groups of either 20 adults or larvae, chose flushing leaves over all reproductive tissues, female flowers, male flowers, and immature fruit. However, to simulate seasons when few flushing leaves were available, additional choice tests were conducted where flushing leaves were omitted, and only reproductive tissues and a filter paper control were included. Individual thrips or groups of either 20 adults or larvae selected all reproductive tissues over controls. When presented with a choice between immature and mature fruit, thrips chose immature fruit. Thrips caused significant damage to live female flowers, male flowers, and immature fruit, and thrips survival rates were similar when fed flush leaves, female flowers, or male flowers. The thrips responses could be tied to VOC production, which significantly varied among tissue types. Volatile blends from flush leaves that include DMNT, Terpinolene, and δ-Elemene may attract P. ichini whereas those that repel them include α-Thujene, α-Pinene, β-Pinene, Camphene, and β-Phellandrene. These results suggest P. ichini has a flexible feeding strategy and exploits Brazilian peppertree reproductive tissues when few flushing tips were available. Further they suggest thrips feeding will have direct impacts on Brazilian peppertree reproduction.

Seasonal Population Dynamics and Harmfulness of Wheat Thrips in Agrocenoses of Grain Crops

The purpose of the study was to identify forage plants and specialized entomophages of wheat thrips in agrocenoses of winter and spring grain crops cultivated in the Samara region. The highest number of adult pests was noted in winter wheat crops (2365.0 ind./100 strokes), the lowest in winter barley crops (565.0 ind./100 strokes). Egg laying by wheat thrip females occurred on all grain crops. Larvae of wheat thrips were noted in the ears of winter and spring wheat, triticale, and winter barley, with the exception of spring barley. During the research, two specialized entomophages were identified: striped thrips and predatory thrips. During the research years, the largest numbers of predatory thrips were noted in winter wheat crops in the earing phase (90 ind./100 strokes) and in spring wheat and spring barley crops in the booting phase—75 ind./100 strokes and 40 ind./100 strokes, respectively. The damage to winter wheat grain by wheat thrips varied from 55.3% to 69.2% and was higher than the damage to spring wheat grain (38.5–64%). With a certain ratio of specialized entomophages and wheat thrips, it is possible to refuse the use of insecticides in the cultivation of grain crops.

ВИДОВОЙ СОСТАВ ТРИПСОВ (INSECTA: THYSANOPTERA) НА СЕЛЕКЦИОННЫХ ПОСЕВАХ ЯРОВОЙ ПШЕНИЦЫ В РГАУ-МСХА ИМЕНИ К.А. ТИМИРЯЗЕВА

Cereal thrips are ubiquitous, widespread and strong pests of grain crops. Imago and larvae of thrips can damage leaves, ears, flowers and grains by injecting and sucking plant juices. Thrips reduce not only the weight but also the sowing qualities of grain, posing a threat to breeding and seed crops. Cereal thrips are a systematically and biologically diverse group of species that are diffi-cult to diagnose and study. Morphological diagnosis of thrips is carried out according to the adult phase; diagnosis of larvae of closely related species requires the use of molecular genetic methods. The wheat thrips are usually the main focus; other species are less known. In the experimental crops in Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, cereal thrips are one of the main pests. In 2020, on spring wheat, their share in the number of insect collections by mowing with a net reached 14 in 2022, it reached 29%. However, the species composition of thrips has not been previously studied here. In the genetic collection of spring wheat (45 varieties) and the collection of endemic wheat (18 varieties) of the breeding experimental station of the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, censuses and diagnostics of the species composition of thrips were carried out. A total of 993 adults of thrips were analyzed and micro preparations were made. Seven species of herbivorous and one species of predatory thrips were identified. The species composition is dominated by three species of cereal thrips: Haplothrips aculeatus, Haplothrips tritici, and Frankliniella tenuicornis. The rarest among them is the rye thrips Limothrips denticornis. Some differences between thrips species are noted in terms of appearance on crops and the period of the main damage. For the most widespread, closely related and outwardly similar species, the main diagnostic features are indicated.

Induced Resistance Combined with RNA Interference Attenuates the Counteradaptation of the Western Flower Thrips.

The western flower thrips, Frankliniella occidentalis Pergande, is an invasive pest that damages agricultural and horticultural crops. The induction of plant defenses and RNA interference (RNAi) technology are potent pest control strategies. This study investigated whether the anti-adaptive ability of F. occidentalis to jasmonic acid (JA)- and methyl jasmonate (MeJA)-induced defenses in kidney bean plants was attenuated after glutathione S-transferase (GST) gene knockdown. The expression of four GSTs in thrips fed JA- and MeJA-induced leaves was analyzed, and FoGSTd1 and FoGSTs1 were upregulated. Exogenous JA- and MeJA-induced defenses led to increases in defensive secondary metabolites (tannins, alkaloids, total phenols, flavonoids, and lignin) in leaves. Metabolome analysis indicated that the JA-induced treatment of leaves led to significant upregulation of defensive metabolites. The activity of GSTs increased in second-instar thrips larvae fed JA- and MeJA-induced leaves. Co-silencing with RNAi simultaneously knocked down FoGSTd1 and FoGSTs1 transcripts and GST activity, and the area damaged by second-instar larvae feeding on JA- and MeJA-induced leaves decreased by 62.22% and 55.24%, respectively. The pupation rate of second-instar larvae also decreased by 39.68% and 39.89%, respectively. Thus, RNAi downregulation of FoGSTd1 and FoGSTs1 reduced the anti-adaptive ability of F. occidentalis to JA- or MeJA-induced defenses in kidney bean plants.

Assessing the Impact of Variety, Irrigation, and Plant Distance on Predatory and Phytophagous Insects in Chili

Chilies are plants that are becoming increasingly popular all over the world, including in Hungary. Since little is known about the abundance and seasonal dynamic of insect pests and their natural enemies associated with chilies under Hungarian climatic conditions, the aim of the study was to monitor these organisms on different varieties under different growing conditions to provide data for improving IPM for chilies. Chili varieties “Yellow Scotch Bonnet” (YSB) and “Trinidad Scorpion Butch T” (TSBT) were planted with three replicates. Two different plant-to-plant distances (30 vs. 40 and 40 vs. 60 cm in YSB, TSBT, respectively) and two different irrigation frequencies (daily, 40 min; every second day, 20 min) were used. Fifty flowers/plot/date were collected. In 2019, Orius (Hemiptera: Anthocoridae) larvae, and in 2021, phytophagous thrips larvae were dominant in all the treatments. Significantly more Orius adults and larvae were found in the YSB than in the TSBT variety and the number of Aeolothrips and phytophagous thrips (Thysanoptera: Thripidae) adults was significantly higher under less irrigation in 2019. The plant spacing did not affect the abundance of predators or herbivores. Upon comparing the two years, no effect of the treatments on the studied insect taxa was observed.

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.

Identification of second instar larvae of thrips (Thysanoptera: Thripidae) vectors of Orthotospovirus (Tospoviridae) in South America

AbstractThrips (Thysanoptera: Thripidae) are the only vectors of Orthotospovirus, a group of viral pathogens that infect plants and cause major economic damage to crops. The virus is acquired by the vector only at the first and early second larval stages and transmitted to plants by adult thrips through the circulatory system and via propagation. Since these vector immatures play a key role in the virus cycle, larval identification can be important for decision‐making about the management of each virus and vector. Thrips identification is mostly based on adult morphology, but second instar larvae recognition can be reliable and may provide advanced diagnosis about the presence and identity of the vector even in the absence of adults. Here, we present an identification tool for second instar larvae of the seven thrips species known to be Orthotospovirus vectors in South America – Frankliniella gemina, F. occidentalis, F. schultzei, F. zucchini, Scirtothrips dorsalis, Thrips palmi and T. tabaci. An illustrated key along with descriptions and comments on each of these species in the continent is provided.

Biology and functional response of the predator, Dortus primarius (Distant) (Hemiptera: Miridae) preying on Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae)

BackgroundDortus primarius (Distant) (Hemiptera: Miridae) is a general predator reported from the oriental region. This bug is naturally found in many crop ecosystems where it feeds on thrips, aphids, insect eggs and other soft-bodied insects. Although, the rearing protocol of this predatory mirid has been developed, the efficiency of this predator as a biocontrol agent is limited and needs to be investigated. The thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae), is a polyphagous pest that attacks many crops in polyhouse in India. Therefore, in the present study, biology and functional response of this predator to different densities of F. schultzei larvae in the laboratory was investigated.ResultsThe mirid predator was able to develop from egg to adulthood on tomato infested plant with F. schultzei larvae in 23–24 days with 15 and 11.76% mortality of 4th and 5th instar nymphs, respectively. Both 5th instar and female adults exhibited a type III functional response. At highest prey density (40) both 5th instar and female adults consumed 21.6 and 28.6 thrips larvae per day, respectively. Functional response parameters, viz. attack rate, handling time, a/Th and T/Th showed the potency of this predator against F. schultzei.ConclusionBased on the high fecundity, predation rate and density dependent behaviour, it is predicted that D. primarius might be an efficient and potential predator. However, further research is needed to assess its release rate and other ecological studies in the field situation.

Spatial and temporal patterns of Frankliniella fusca (Thysanoptera: Thripidae) in wheat agroecosystems

AbstractFrankliniella fusca Hinds (Thysanoptera: Thripidae) is an economically important pest of many cultivated crops including cotton, tomatoes, peppers and tobacco. Previous research has focused on the importance of non‐crop weeds for F. fusca populations when estimating crop infestation risk in the spring. Although weeds play an integral role in population development, early‐season cultivated hosts (e.g. wheat and sage) may also contribute and augment overall populations. Few studies have examined the role of early‐season crops as a source habitat for sensitive host crops later in the season. The goal of this study was to investigate the abiotic conditions and landscape components that are associated with F. fusca populations in winter wheat (Triticum aestivum L.). Exploring these relationships will provide insight into early‐season drivers of F. fusca. To do this, we conducted a 2 year study documenting F. fusca populations during an 8 weeks period each spring. We sampled immature thrips abundance on wheat heads while concurrently monitoring adult dispersal from the field using yellow sticky cards. Across both years, we found that immature thrips sampled during the milk and dough development stages best‐predicted adult dispersal 2 weeks later. Cumulative precipitation and the number of precipitation events beginning in the autumn of the prior year were the most important abiotic predictors of F. fusca abundance. At the landscape scale, adult F. fusca density was negatively related to the area of row crop agriculture, grasslands and amount of landscape fragmentation. Results of our study provide a basis to assess larval thrips and forecast dispersal of this pest from wheat using a head sampling method. At a landscape scale, we show that specific combinations of abiotic and landscape variables influence population abundance of F. fusca in North Carolina row crop agroecosystems.

Identity and Population Density of Thrips hawaiiensis (Insecta: Thysanoptera) in Conventional “Magallanes” Pummelo Orchard in Carmen, Davao del Norte, Philippines

A conventional “Magallanes” Pummelo orchard in Brgy. Minda, Carmen, Davao del Norte, Philippines was selected to assess thrips species composition, population density, and associated natural enemies. The insecticide treated pummelo orchard was situated adjacent to vast Cavendish banana plantations. Thrips were collected weekly from September 2017 to July 2018 from five different randomly selected flowering pummelo trees by destructive sampling and yellow sticky trap methods. Thrips were sorted and examined under the microscope. Findings of the study showed that Thrips hawaiiensis (Morgan), (Thripidae: Thripinae) was the only species of thrips infesting “Magallanes” pummelo. This constitutes the first report in this host variety. Thrips hawaiiensis population fluctuated within the six phenological stages of pummelo fruiting cycle but was significantly high at the peak of flowering stage. Population started to decline at petal fall and fruit development stages although the pummelos still produced small numbers of new terminal shoots. These shoots provided stable food source for remaining thrips larvae. Population was significantly low when the fruits are at harvestable stage (p < 0.01). Among the weather variables monitored temperature had very low coefficient value (r = 0.09) with a positive relationship to thrips population; however, together with rainfall and relative humidity, statistical significance value did not significantly (p > 0.05) influence thrips population. Furthermore, absence of parasitoids during the whole duration of the study may have been affected by the conventional pest management continuously being practiced by plantation owners of using broad spectrum insecticides that may have affected the non-target species in the area.