Thrips Populations Research Articles

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

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

Effect of Novel Insecticides on Sucking Pests and Pink Bollworm in Cotton Plants under Field Conditions

The study investigated that the effectiveness of various novel insecticides for controlling sucking pests and pink bollworm in cotton cultivation over a three-year period. The treatments were evaluated based on their impact on aphids, jassids, thrips, whiteflies and pink bollworm populations. During 2018-19, 2019-20 and 2020-21 years, among the tested novel insecticides, Fipronil + Imidacloprid @ 100g/ha has recorded lowest population of thrips, jassids. Similarly, Fipronil+ Acetamiprid @ 1000 ml/ha has recorded lowest aphid population whereas incidence of pink bollworm was least in Lamdacyhalothrin + Chlorantraniliprole @ 200 ml/ha.

Field Evaluation of Biorationals and Chemical Insecticides against Thrips parvispinus (Karny) (Thysanoptera: Thripidae), in Chrysanthemum

Field study was conducted to evaluate the efficacy of biorationals and chemical insecticides against black thrips, Thrips parvispinus (Karny) on chrysanthemum. Thrips population ranged from 15.33 to 13.89/flower before spraying. The efficacy of seven biorationals and seven chemical insecticides were evaluated against black thrips under field conditions. The application of pongamia soap @5g/lit and Spinosad 45% SC @ 0.2 ml/lit reduced the thrips incidence significantly among the biorational and chemical insecticides respectively. The mean per reduction of thrips incidence in pongamia soap @ 5 gm/lit application was 74.90%. This was followed by neem soap @ 5g/lit (72.25%), azadirachtin @10000ppm (71.10%), Beauveria bassiana (66.76%), Isaria fumosorosea (64.93%), Lecanicillium lecanii (63.72%), and Metarhizium anisopilae (62.46%). Among the chemical insecticides Spinosad 45%SC @ 0.2 ml/lt. stood first in the order of efficacy with 80.2% reduction in thrips population. The order of efficacy of chemical insecticides against black thrips in chrysanthemum are spinetoram 11.7%SC (76.245%) > cyantraniliprole 10%OD (73.92%) > fipronil 5% SC (72.24%) > thiamethoxam 25% WG (70.79%) > dinotefuran 20% WG (69.80%) > tolfenpyrad 15% EC (68.02%). The effective biorational and chemical insecticide can be included as a component in the Integrated pest management of thrips complex in chrysanthemum. The rotation of effective compounds will reduce the resistance development against insecticides in thrips associated with chrysanthemum and also reduces the thrips infestation.

Genetic diversity of thrips populations on Allium species around the world.

Thrips are a serious pest in many crops. In onion cultivation, Thrips tabaci is the most important, but not the only thrips species causing damage. We investigated which thrips species affects onion and related species worldwide, how much genetic variation there is within T. tabaci populations, and how this evolves. Furthermore, we determined the reproductive mode and the correlation between the genetic and geographic distances. Thrips samples from infested onions or related species were obtained from 14 different locations worldwide. Species and haplotypes were determined through DNA barcoding with the mitochondrial Cytochrome Oxidase subunit I (COI) gene. Thrips tabaci was the most commonly observed species, but Scirtothrips dorsalis, Thrips palmi, Frankliniella intonsa, Frankliniella occidentalis and Frankliniella tenuicornis were also found, especially at the beginning of the growing seasons and depending on the location. The Nei's genetic distance within T. tabaci was less than 5% and the haplotypes were clustered into two phylogenetic groups, each linked to a specific mode of reproduction, thelytokous or arrhenotokous. Thelytokous thrips were more common and more widely distributed than arrhenotokous thrips. A high percentage of heteroplasmy was detected in the arrhenotokous group. Heteroplasmic thrips were only found in populations where thelytokous and arrhenotokous were present in sympatry. Some T. tabaci haplotypes were present in high frequency at several sampled locations. No correlation was found between the genetic and geographic distances, which points to anthropic activities spreading thrips haplotypes throughout the world.

First report of Groundnut ringspot virus (GRSV) infecting tobacco (Nicotiana tabacum L.) in South Africa.

Tobacco (Nicotiana tabacum L.) is an important industrial crop from the Solanaceae family cultivated for its leaves in approximately 100 countries worldwide. In South Africa (SA), tobacco is grown in five of its nine provinces: Limpopo, North West, Western Cape, Eastern Cape, and Mpumalanga. The producer price for unmanufactured tobacco is approximately US$3570/ton annually (FAO, 2021). Emerging and recurrent plant viruses such as tomato spotted wilt orthortospovirus (TSWV) have seriously affected tobacco production yield and quality. Between November 2018 to April 2019 growing season, large thrips (order Thysanoptera) populations were observed in tobacco fields throughout South Africa's major tobacco-growing areas, and plants were showing severe necrosis, yellowing, stunted growth, ringspot, and leaf curling symptoms, which are usually associated with plant virus infections. The disease incidence was estimated at 30%, as per visual observations. Twenty-two symptomatic leaf tissue samples were collected from tobacco farms in Limpopo, Northwest, and Western cape provinces. Samples were initially screened using the double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with LOEWE®Fast Kit (LOEWE®, Germany), which detectsTSWV, groundnut ringspot orthotospovirus (GRSV), and tomato chlorotic spot orthotospovirus (TCSV). Nineteen of these samples tested positive for orthortospoviruses. Subsequently, a reverse transcription-polymerase chain reaction was performed on all ELISA-positive samples using orthotospovirus-specific primers gM410 & gM870c targeting the NSm gene (Chen et al., 2012). All samples were positive for orthotospoviruses, as indicated by the presence of a 500bp amplicon. Nineteen purified PCR products were sequenced in the forward and reverse directions using Sanger sequencing at the KwaZulu-Natal Research and Innovation Sequencing Platform (KRISP; South Africa). The sequences were aligned using Muscle in MEGA version X (Kumar et al., 2018) to generate the consensus sequences that were then subjected to the standard nucleotide basic local alignment search tool (blastn) on the NCBI website. Blastn analysis showed that 16 of the 19 samples matched TSWV nucleotide sequences, while three of the sequences; LP14 (accession number OL505552), LP18 (accession number OL505553), and NW4 (accession number OL505554), had a nucleotide sequence identity of 96,38%, 96,97% and 97,29% with the GSRV isolate SA-05 (accession number MH742957; Silva et al., 2019) from South Africa, respectively. This is the first report of GRSV infecting tobacco after TSWV was reported in SA. Previously, GSRV was reported on soybean and groundnut in South Africa by Petersen and Morris in (2002) and Silva et al. in (2019). The results from this study lay a foundation for more detailed studies on GRSV, which will result in the development of effective and sustainable control strategies to manage GRSV diseases on tobacco in SA.

An intelligent fuzzy system to manage western flower thrips population under biological treatment in roses yield

Experimentation centers in the French Riviera (SCRADH, Florisud, and others) are keen on informing growers about the propitious weather conditions relative to pest risk growth. The only existing method used nowadays is sending notifications to their mobile phones. In this study, we are interested in developing a system for Western Flower Thrips (WFT) risk assessment. We propose a fuzzy logic approach to build an intelligent system that supplies rose growers with an estimate of the next day’s risk in their greenhouses. The system relies on today’s data (data of the day) to predict the next day’s risk, under the presence of bio-control agents, in particular, harmless fungi called Beauveria Bassiana. We could recapitulate the study’s outcomes in the following elements. The most significant aspect is estimating a daily risk index that provokes premature detection of WFT. Besides, considering the utilization of biological treatment aids in reducing the pulverization of pesticides. In addition, the system incorporates a small number of sensors usually found in almost all greenhouses. Thanks to continuous monitoring of the weather conditions (real-time system), the system could help mitigate the percentage of yield loss. Finally, this is the first attempt to employ fuzzy logic to predict WFT subjected to biological treatment. We compared the obtained results to actual data. The model’s accuracy was determined by three statistical indicators (coefficient of determination (R2), root mean squared error (RMSE), and mean absolute error (MAE)) showing a noticeable performance. The fuzzy model showed satisfactory results (R2=0.9, RMSE= 10%, and MAE=7.3%) making it reliable and robust for pest monitoring.

Overview of Updated Control Tactics for Western Flower Thrips.

Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), broadly known as Western flower thrips (WFT), are currently one of the most critical pests worldwide in field and greenhouse crops, and their management is full of yet unsolved challenges derived from their high reproductive potential, cryptic habit, and ability to disperse. The control of this pest relies widely on chemical control, despite the propensity of the species to develop resistance. However, significant advances have been produced through biological and ethological control. Although there has recently been a remarkable amount of new information regarding the management of this pest worldwide, there is no critical analysis of recent developments and advances in the attractive control tactics for WFT, constituting the present compilation's aim. Hence, this narrative review provides an overview of effective control strategies for managing thrips populations. By understanding the pest's biology, implementing monitoring techniques, accurately identifying the species, and employing appropriate control measures, farmers and researchers can mitigate the WFT impact on agricultural production and promote sustainable pest management practices.

Distribution of Scirtothrips dorsalis (Thysanoptera: Thripidae) cryptic species complex in the United States and reproductive host assessment of its dominant member.

Chilli thrips, Scirtothrips dorsalis Hood, is a cryptic species complex of at least 9 species, 2 of which (South Asia 1 and East Asia 1) have been confirmed damaging >50 plant taxa in the United States. To develop a knowledge-based management program for this pest in the United States, the objectives of the study were to (i) survey for S. dorsalis species complex in the suspected regions and (ii) assess the reproductive hosts of the predominant member available. Thrips samples received from collaborators were subjected to morpholo-molecular characterization. Of the 101 thrips populations received across the United States between 2015 and 2021, 71 populations were confirmed as S. dorsalis, with ~25% further identified as East Asia 1, compared with ~41% identified as South Asia 1, suggesting the latter species is more prevalent in the US. East Asia 1 was primarily found in samples collected from Hydrangea sp. (95%) in Massachusetts, New York, and Pennsylvania, indicating geographic range expansion in the Northeast and successful overwintering in areas with hard freezes. While assessing the host range of South Asia 1 (dominant species), 62 plant taxa were evaluated under greenhouse conditions. Among these, 40 feeding and reproductive hosts were confirmed in Florida. We also found 18 new reproductive hosts and 3 feeding hosts of S. dorsalis, which were not previously reported in the literature. The results provide insight into the increasing host range and expanded geographical distribution of S. dorsalis species and will enable the development of a species-specific monitoring and management program.

Using perennial groundcover crops to suppress weeds and thrips in the southeast cotton belt

AbstractModern cotton production (Gossypium hirsutum L.) in the United States relies on chemical and physical inputs that increase the environmental and monetary costs of managing the crop. Perennial groundcover crops (PGCC) may reduce inputs by persisting in the interrow spaces of the cotton crop during summer months. A 2‐year field study was conducted in Florence, SC, to evaluate growing PGCCs with cotton using a 4 × 4 Latin square consisting of four cover crop treatments: (1) a fallow, unplanted control, (2) annual ryegrass (Lolium multiflorum Lam.) monoculture, (3) a binary red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) mixture, and (4) a trinary mixture of annual ryegrass, red clover, and white clover. Fallow and annual ryegrass treatments were killed with a burndown herbicide application, while treatments containing clovers were mowed. Plots were strip‐tilled and planted with cotton in May each year. Interrow biomass, weed and thrips populations, and perennial clover populations were collected from June to October along with annual lint yields from cotton harvest in October. Results indicated that interrow biomass (2000–3000 kg ha−1), weeds (20 weeds m−2), and thrips (five thrips per five plants−1) populations were lowest in treatments containing perennial clovers, but drought and heat stress reduced clover stands within two growing seasons. Lint yield was not affected by incorporating perennial clovers into the interrow spaces of the crop. Perennial groundcover crops may provide an effective alternative to chemical weed control in cotton, but necessitate management changes to be viable in the southeastern United States.

Evaluation of efficacy of different concentrations of newer insecticides againstthrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) infesting castor

Field experiment was conducted at Centre for Oilseeds Research, S.D. Agricultural University, Sardarkrushinagar, Gujarat India during 2018-2019, 2019-2020, 2020-21 and 2021-22 to evaluate the efficacy of three newer insecticides (acetamiprid 20 SP, clothianidin 50 WDG, flonicamid 50 WG) with different concentrations (lower, normal and higher dose) against thrips (Scirtothrips dorsalis) infesting castor. Based on pooled analysis of four years data, mean population of thrips were found lower in plots treated with flonicamid 50 WG @ 0.019% (36.35 thrips/tender spike/plant), flonicamid 50 WG @ 0.015% (37.57 thrips/tender spike/plant) followed by flonicamid 50 WG @ 0.011% (39.16 thrips/tender spike/plant) and acetamiprid 20 SP @ 0.004% at its normal dose recorded 40.02 thrips/tender spike/plant which are at par with each other. The treatments acetamiprid 20 SP @ 0.005% and clothianidin 50 WDG @ 0.031% observed 40.21 and 40.58 thrips/tender spike/plant, respectively. Maximum seed yield of castor was realized from the acetamiprid 20 SP @ 0.005% treated plots (2284 kg/ha) followed by flonicamid 50 WG @ 0.019% (2220 kg/ha) and flonicamid 50 WG @ 0.015% (2148 kg/ha), which were at par with each other, whereas the lowest seed yield was recorded in control (1910 kg/ha). The maximum net gain (`24945/ha) and benefit-cost ratio (1:11.50) was obtained with application of acetamiprid 20 SP @ 0.005% followed by acetamiprid 20 SP @ 0.004 % (`6245/ha and 1:3.09) and flonicamid 50 WG (`16622/ha and 1:2.84).

Relationship of weather parameters and date of showing on vector-borne disease, stem necrosis of potato

Stem necrosis is a hot spot disease caused by Tospovirus, a groundnut bud necrosis virus strain for Rajasthan. The minimum per cent incidence (5.56%) of stem necrosis was recorded with the variety Kufri Sindhuri and Kufri Pushkar (7.69%), while the maximum per cent incidence (24.87%) in Kufri Pukhraj and Kufri Bahar (23.75%). Out of three sowing dates, minimum disease incidence was recorded on 3rd planting date. The maximum and minimum temperature was highly significant, with a positive correlation against stem necrosis on the first planting date. A highly significant positive correlation between stem necrosis and the thrips population was detected. The maximum area under the disease progress curve (AUDPC) value was found on 1st date of sowing. The 3rd date of sowing produced the maximum number of tubers per plot, marketable yield and total tuber yield (q/ha). However, the maximum per cent dry matter was recorded in K. Sindhuri (22.27%) and K. Pushkar (21.01%). Thus, the experiment results suggested that the variety of Kufri Sindhuri and Kufri Pushkar with planting in the last week of October caused a significant reduction in stem necrosis disease leading to a corresponding increase in tuber yield of potato.

Use of sugars as alternative to chemical control: trials carried out on thrips associated with olive tree

Foliar spraying of infradoses of sugars (glucose, fructose or sucrose) induces plant resistance to pests that are particularly difficult to combat. These include thrips, which can cause flower abortion, stunting and deformation of olives, resulting in significant crop losses. Randomised block trials were conducted during three years (2017 to 2019), on two cultivars Chemlal and Sigoise, in an olive grove in Batna province (Algeria), with the aim of determining the most effective dose and type of sugar on thrips populations, and to evaluate the effectiveness of combining sugar with chemical treatment, as well as the possibility of reducing the dose of the latter. The results showed that sucrose at a concentration of 100 ppm was the most effective and that the efficacy of sucrose was higher than that of glucose and fructose, on both cultivars tested. The combination of sucrose with insecticide resulted in a synergistic effect and a higher efficacy gain than sucrose alone, and that the efficacy of the combination sucrose + insecticide at low dose D1 was identical to the combination sucrose + insecticide at recommended dose D2. It is therefore possible to reduce the chemical insecticide dose while maintaining good treatment efficacy for the control of these pests.

Efficacy of Some Insecticides Against Thrips and Yellow Mites in Chilli

Efficacy of some insecticides new chemistry insecticides was evaluated against chilli thrips Scirtothrips dorsalis and yellow mite Polyphagotarsonemus latus, during kharif, 2019 and green and red chilli samples were subjected to residue analysis to evaluate the persistence of sprayed pesticides. Spinetoram 11.7SC at 60 g a.i./ ha was observed to be superior in managing chilli thrips with a mean reduction of 93.35% with least thrips population (0.53/ top 3 leaves) followed by cyantraniliprole 10.26OD at 60 g a.i./ ha and spirotetramat 15.31OD with 90.78 and 85.44 mean % reduction, respectively. Management of yellow mites was effective in plots treated with abamectin 1.9EC at 7 g a.i./ha of 85.73 mean per cent reduction followed by chlorfenapyr 10SC at 100 g a.i./ ha (83.48%) and emamectin benzoate 5SG at 10 g a.i./ ha (76.64%). Lambda-cyhalothrin and chlorantraniliprole residues were detected in green and red chilli among the sprayed pesticides.

Production and quality of Hami melon (Cucumis melo var. reticulatus) and pest population of Thrips palmi in UV-blocking film greenhouses.

Ultraviolet (UV) interferes with the vision, flight initiation, dispersal, host, and population dispersion of herbivorous insects. Hence, UV-blocking film has recently been developed as one of the most potential tools to control pests under tropical greenhouse conditions. In this study, we investigated the effects of UV-blocking film on the population dynamics of Thrips palmi Karny and the growth status of Hami melon (Cucumis melo var. reticulatus) in greenhouses. By comparing thrips populations in greenhouses covered with UV-blocking films with those covered with ordinary polyethylene films, we found that the UV-blocking film effectively reduced the thrips population within 1 week and continued to control the population, meanwhile the quality and yield of melon in UV-blocking greenhouses also had a substantial increase. The UV-blocking film remarkably inhibited the population growth of thrips and greatly improved the yield of Hami melon cultivated in UV-blocking greenhouse compared with the control greenhouse. Overall, UV-blocking film is a very powerful potential tool for green pest control in the field, enhancing the quality of tropical fruits, and providing a new wind vane for sustainable green agriculture in the future. © 2023 Society of Chemical Industry.

Emergence of less effective insecticidal populations of flower thrips, <i>Frankliniella intonsa</i> (Trybom) for spinosad in a strawberry greenhouse in Nara Prefecture

We identified spinosad-resistant populations of Frankliniella intonsa (Trybom) in strawberry greenhouses in Nara city and Kashiba city. The mortality rate of the Kashiba population for spinosad commercial concentration was 6.5%, but that of the Nara population was 86.2%. This suggested that F. intonsa collected from strawberry in Nara Prefecture developed resistance to spinosad.

AKURASI PENILAIAN SERANGAN Thrips sp. PADA DAUN CABAI BERDASARKAN PENGAMATAN VISUAL DAN PENGOLAHAN CITRA

Visual observation is a method of assessing the intensity of thrips infestation that assessors favor because it is relatively easy to apply. However, on the other hand, it has many limitations. Therefore, a more accurate alternative method, such as digital image processing, is needed. This study aims to evaluate the accuracy of visual observation and digital image processing used to assess the thrips attack on cayenne pepper leaves. This study was designed following a Randomized Group Design with four treatments, namely P1 (1), P2 (3), P3 (5), and P4 (7 thrips/container cup). Each treatment was repeated three times (12 experimental units), and each experimental unit used five test leaves. The variable observed was the accuracy of assessing thrips attack intensity on chili leaves based on visual observation and image processing. The results show that high thrips populations can cause high attack intensity on chili plants based on visual observation results, while based on image processing, it is known that high thrips populations do not necessarily cause high attack intensity. The assessment of attack intensity based on visual observation provides a lower accuracy level than image processing. The results of the assessment of attack intensity based on visual observations are less reliable because there is a bias of 0.67.

The influence of agent density for biological control of young Brazilian peppertree (Schinus terebinthifolia) with the Brazilian peppertree thrips (Pseudophilothrips ichini)

ABSTRACT Brazilian peppertree, Schinus terebinthifolia Raddi (Sapindales: Anacardiaceae), is an invasive tree in the Southeastern United States, Texas, California, and Hawaii. The Brazilian peppertree thrips, Pseudophilothrips ichini Hood (Thysanoptera: Phlaeothripidae), is a recently approved biological control agent for use within the US. The thrips have since been released in the field and are expected to reduce Brazilian peppertree performance. Pseudophilothrips ichini is likely to impact young trees but the impacts may vary based on thrips population size and tree age. To better understand the factors contributing to agent impact on young trees and P. ichini population growth, we measured the effect of P. ichini density (0, 4, 10, and 20 thrips) and tree age (3-, 4-, and 6-month-old plants), on tree performance and P. ichini productivity in the laboratory. Brazilian peppertree height and the number of growing tips were reduced across all age groups. However, the negative impact was more pronounced on the youngest trees, which had a reduction in the relative change in height of 171% and a 100% reduction in the number of growing tips. Pseudophilothrips ichini production was positively correlated with tree height (r = 0.44) and biomass (r = 0.56), but thrips relative production was similar across tree age. Results indicate that P. ichini have a great capacity for population increase regardless of starting density. Field studies are needed to corroborate these findings and identify barriers to agent success. This work aims to refine expectations of the impacts to Brazilian peppertree caused by P. ichini.

Population performance and detoxifying and protective enzyme activities of four thrips species feeding on flowers of Magnolia grandiflora (Ranunculales: Magnolia).

Different thrips species can co-occur on the same flowers with different dominance degrees. To accurately evaluate the population performance on different thrips species on Magnolia grandiflora flowers, we investigated the diversity of thrips species and their population dynamics both in the field and laboratory. In addition, the activities of detoxifying and protective enzymes in thrips were also measured. Field investigations revealed that four thrips species (Thrips hawaiiensis, Thrips flavidulus, Frankliniella occidentalis, and Thrips coloratus) coexisted on M. grandiflora flowers. They were ranked, from highest population density to lowest, as follows: T. hawaiiensis > T. flavidulus > F. occidentalis > T. coloratus. In laboratory investigations, the species were ranked, from fastest developmental rates to slowest, as follows: F. occidentalis > T. hawaiiensis > T. flavidulus > T. coloratus; and from largest population size to smallest, as follows: T. hawaiiensis > F. occidentalis > T. flavidulus > T. coloratus. Biochemistry assays showed that the four species differed in their activities of detoxifying enzymes (carboxylesterase, glutathione-S-transferase, and cytochrome P450) and protective enzymes (superoxide dismutase, peroxidase) in both laboratory and field strains. Differences in population performance among these four thrips on M. grandiflora may be related to their activity levels of physiological enzymes. The variations in thrips population performance between the field and the laboratory could be due to differences in environmental conditions. T. hawaiiensis showed a strong host preference for M. grandiflora, and thus it has the potential to be a dangerous pest in horticultural plants. © 2023 Society of Chemical Industry.

Screening of Germplasms and Population Dynamics of Major Insect Pests of Spring Green Gram Vigna Radiata (Linn.)

The present investigation was conducted during Spring season of 2021-22 at Norman. E. Borlaug. Crop Research Centre of G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand) and Morphology laboratory of Department of Entomology with the objectives screening of green gram germplasms in field as well as laboratory conditions and occurrence of major insect pests in field conditions. In field conditions major insect pests were observed using various methods such as whiteflies in a whitefly cage, jassids/trifoliate, knockdown approach for thrips and sweep net method for pod bug population. Under laboratory conditions germplasms were screened against Spodoptera litura using choice test method. Investigations on population dynamics shows that population of whitefly was highest during 17th SMW while thrips population was at peak during 19th SMW followed by jassid in 17th SMW and pod bugs in 19th SMW. Based on data recorded among various entries SSME 21-70, SSME 21-55 and SSME 21-53 were found superior among all the test entries against B. tabaci, M. distalis, E. kerri and C. gibbosa infesting green gram. Data of laboratory experiments revealed that when castor was used as standard host, preference index varied significantly from 0.02 (SSME 21-48) to 1.00 (SSME 21-55) at P = 0.05 level of significance while when PM-5 was taken as standard host, significant variation in preference index was recorded from SSME 21-70 (0.01) to SSME 21-43 (1.16) at P = 0.05.

Interspecific and intraspecific variation in susceptibility of two co-occurring pest thrips, Frankliniella occidentalis and Thrips palmi, to nine insecticides.

Field control of pest thrips mainly relies on insecticides, but the toxicity of insecticides can vary among thrips species and populations. In this study, we examined the susceptibility of multiple field populations of two thrips pests, Frankliniella occidentalis, and Thrips palmi, that often co-occur on vegetables, to nine insecticides belonging to seven subgroups. The highest level of variation in susceptibility among F. occidentalis populations was for spinetoram (73.92 fold difference between most resistant and most susceptible population), followed by three neonicotinoids (8.06-15.99 fold), while among T. palmi populations, it was also for spinetoram (257.19 fold), followed by emamectin benzoate, sulfoxaflor, and acetamiprid (23.64-45.50 fold). These findings suggest evolved resistance to these insecticides in some populations of the two thrips. One population of F. occidentalis had a particularly high level of resistance overall, being the most resistant for five of the nine insecticides tested. Likewise, a population of T. palmi had high resistance to all nine insecticides, again suggesting the evolution of resistance to multiple chemicals. For F. occidentalis, the LC95 values of most populations were higher than the field-recommended dosage for all insecticides except chlorfenapyr and emamectin benzoate. For several T. palmi populations, the LC95 values also tended to be higher than recommended dosages, except in the case of emamectin benzoate and spinetoram. Our study found interspecific and intraspecific variations in the susceptibility of two thrips to nine insecticides and multiple resistance in some populations, highlighting the need for ongoing monitoring and resistance management. © 2023 Society of Chemical Industry.