Thrips Densities Research Articles

Efficiency of Some Chemical and Bio-Insecticides Against Onion Thrips, Thrips Tabaci Lindeman (Thysanoptera: Thripidae)

Onion thrips, Thrips tabaci (Thysanoptera: Thripidae) is one of the main problems and yields limiting factors in the onion fields (Allium cepa L.). In the present work, an effort was made to study the relative susceptibility of different onion cultivars to infestation with the onion thrips, evaluation of some chemical and bio-insecticides against T. tabaci and to study the effect of meteorological factors on its population density. The results showed that T. tabaci infest all the tested cultivars more or less, however cultivar Red Giza showed to be the most tolerant against T. tabaci infestation among the other cultivars. Giza 6 was the most susceptible among the cultivars followed by Beheri, Giza 20 and finally White Giza. However, there were no significant different among the White Giza and Red Giza cultivars.The tested insecticides can be arranged according to their efficacyagainst nymphs of T. tabaci in descending order as follows; spinetoram, pyridalyl,imidacloprid, thiamethoxam, lambda-cyhalothrin, dinotefuran, pyriproxyfen, malathion, azadirachtin and finally Beauvaria bassiana. On the other hand, these insecticides can be arranged according to the general means of reduction percentages of T. tabaci adults in a descending order as follows; pyridalyl, spinetoram, thiamethoxam, imidacloprid, lambda-cyhalothrin, dinotefuran, pyriproxyfen, malathion, Beauvaria bassiana and azadirachtin.The results of the population trends of T. tabaci revealed that the onion thrips had two generations during the onion growing period. There was a significantly negative correlation (P˂0.05) between population density of onion thrips and relative humidity. The results also revealed that the temperature positively and significantly affect T. tabaci population in both seasons2020 and 2021.

Assessing the temporal dynamics of Frankliniella schultzei (Thysanoptera: Thripidae) in commercial soybean crops in North Brazil

Abstract Thrips are considered a secondary pest of soybean in Brazil, but high densities have been noticed since the last harvests (2017/18 and 2018/19), yet no study has provided an initial hypothesis regarding the causes of such events. We aimed to identify some of the factors related to Frankliniella schultzei Trybom (Thysanoptera: Thripidae) temporal dynamics in commercial soybean crops located in Tocantins (Northern Brazil). We undertook evaluations during soybean vegetative, flowering, and fruiting stages on 200 plants per field in each sampling date (n = 22). Our results indicated that the densities of F. schultzei were similar among fields and soybean phenological stages. The density of thrips showed a significant negative relationship with rainfall, but it was not related to either air temperature, photoperiod, relative humidity, or wind speed. The predators' density was less than 170 individuals (summing all assessments), and it was not associated with thrips density. This study indicates rainfall as the leading factor associated with the temporal dynamics of F. schultzei in commercial soybean crops.

Using wind vanes to study how thrips reach colored traps

AbstractIn agricultural crops, colored traps are often used to monitor the density of thrips (Thysanoptera: Thripidae), important pests and vectors of viral diseases. We used colored pole traps, mounted on wind vanes, to study thrips approach in two countries. In Israel, during periods of low wind speed (<1.1 km h‐1), 77% of western flower thrips, Frankliniella occidentalis (Pergande), reached the leeward side of traps by actively flying upwind. In New Zealand, during periods of high wind speed (>9 km h‐1), 83% of onion thrips, Thrips tabaci Lindeman, reached the windward side of traps passively. Consequences of these results for thrips monitoring are discussed.

Population dynamics of Frankliniella occidentalis Pergrande and its predator Orius similis Zheng on common crops and surrounding plants

• Plants surrounding Capsicum annuum fields can provide habitat for predator Orius similis . • Hypericum beanii and Trifolium repens are the important sources of Frankliniella occidentalis on C. annuum . • Zea mays is the potential banker plant of O. similis in C. annuum planting. Frankliniella occidentalis Pergrande is important invasive pests in China, causing damage to agricultural production, and Orius similis Zheng is the dominant predator species of F. occidentalis . A two-year survey was conducted to determine the population density of F. occidentalis and O. similis , on chili ( Capsicum annuum L.) and maize ( Zea mays L.) crops and surrounding weed species, which included white clover ( Trifolium repens L.), St. John's wort ( Hypericum beanii N. Robson), alfalfa ( Medicago sativa L.) and beggarticks ( Bidens pilosa L.) in Kunming, southern China. The activity of F. occidentalis on these 6 host plant species was determined using the quartile method. F. occidentalis mainly damaged plants during their flowering stage. The main activity period of F. occidentalis occurred earlier on H. beanii and T. repens than on C. annuum . The peak activity of F. occidentali s occurred in the middle of May (on T. repens ). During the whole activity period, the highest thrips densities were recorded on H. beanii among all of the sampled host plant species, followed by C. annuum . The lowest density was recorded on B. pilosa . Dynamics of immature F. occidentali s were more irregular than that of adults. The highest density of O. similis was recorded on Z. mays . It was 2.27–26.43-fold (2017) and 2.01–19.09-fold (2018) higher than that on other host plant species. This study showed that F. occidentali s could migrate between C. annuum and surrounding weeds. The weeds were the main source of thrips on C. annuum . The results indicated that Z. mays can be planted around C. annuum fields as a potential banker plant, to attract O. similis to control F. occidentalis on C. annuum , T. repens and B. pilosa . The flowering period of plants and surrounding plant species has a great effect to the population activities of F. occidentalis and predator O. similis on crops.

Thrips (Thysanoptera: Thripidae) in northern Tunisian citrus orchards: population density, damage and insecticide trial for sustainable pest management

Thrips (Thysanoptera: Thripidae) have been considered serious pests infesting a wide range of host plants around the world, which has also been the case for citrus trees in Tunisia, a South Mediterranean country. The present study was performed to refine our knowledge about density and damage of the most common, emerging thrips species on Navel oranges in northern Tunisia, and to evaluate the effectiveness of three insecticides in decreasing density of thrips and their induced damage. Populations of the three thrips species, Pezothrips kellyanus, Thrips major and Frankliniella occidentalis, on citrus flowers increased from March to June with F. occidentalis being the most common species found as larval and adult stages on either orange flowers or fruits. Two types of thrips blemishes on Navel orange were observed: ring-shaped silvery scaring, and marbling damage for which a positive and significant correlation was revealed with western flower thrips F. occidentalis. All tested insecticides (spinosad, acrinathrin and terpenoid) were effective in decreasing F. occidentalis population density on Navel orange trees, with both biopesticides spinosad and terpenoid being the most effective one day after treatment, while the chemical insecticide acrinathrin proved to be the most effective 7, 17 and 21 days after treatment. Furthermore, spinosad and terpenoid applications resulted in the lowest marbling damage percentage (4% and 6%, respectively) compared to acrinathrin (26%). The implications of the obtained findings for improving integrated pest management of thrips in Tunisian citrus orchards are highlighted and discussed herein.

Management of Onion Thrips (Thrips tabaci) in Organic Onion Production Using Multiple IPM Tactics.

Simple SummaryOnion thrips (Thrips tabaci) is a major pest in organic onion production and effective integrated pest management strategies are lacking. Our objective was to evaluate pest management programs consisting of several different tactics: (1) two onion plant cultivars with semi-glossy leaves (“Rossa di Milano” and B5336AxB5351C) and one with waxy leaves (“Bradley”), (2) silver reflective and white plastic mulches, and (3) with or without an application of a biopesticide (spinosad + neem oil tank mix). Thrips densities were counted weekly and bulbs weighed at harvest. The application of the biopesticide had the most significant reduction in thrips densities and increase in yield. The cultivar “Rossa di Milano” had lower thrips densities compared with “Bradley” and B5336AxB5351C, but also had the lowest yield. Reflective mulch had lower thrips densities than white mulch but had no effect on yield. None of the other tactics provided any significant additional benefits to thrips management. While biopesticides will still be a key component to onion thrips management programs, their application frequency should be further optimized.Onion thrips (Thrips tabaci Lindeman) is a major pest in organic onion production and effective integrated pest management strategies are lacking. Our objective was to evaluate combinations of semi-glossy (“Rossa di Milano” and B5336AxB5351C) and waxy (“Bradley”) onion cultivars with reflective mulch, with or without biopesticides (spinosad + neem oil tank mix), to manage T. tabaci in organic onion production. Thrips densities were assessed weekly and bulbs graded and weighed at harvest. Onions sprayed with spinosad + neem oil had fewer T. tabaci (adults: 74% (2019); larvae: 40% (2018), 84% (2019) and produced higher yields (13% (2018), 23% (2019)) than onions that were unsprayed, regardless of mulch type or onion cultivar. “Rossa di Milano” had relatively fewer adult and larval thrips populations compared with “Bradley” (21% (2018), 32% (2019)) and B5336AxB5351C. However, “Rossa di Milano” had the lowest marketable yield in both years. Reflective mulch reduced densities on certain dates in both years compared to white mulch, but the largest and most consistent reduction only occurred in 2019. Reflective mulch had no impact on bulb yield. While spinosad + neem oil reduced thrips numbers and increased yield alone, none of the treatment combinations were effective at suppressing populations of thrips. Future T. tabaci management in organic onions will require optimization of the available effective biopesticides.

Physiological and biochemical response of differentresistant alfalfa cultivars against thrips damage.

To investigate physiological and biochemical changes of thrips-resistant alfalfa (Medicago sativa L. cv. Gan-nong No. 9), we aimed at clarifying the response mechanisms of alfalfa against thrips. Medicago sativa L. cv. including thrips-resistant Gan-nong No.9 (G9), thrips-susceptible Gan-nong No.3 (G3) and highly thrips-susceptible WL363HQ (363) were infested with different thrips densities (3, 5, 7 and 9-thrips per branch). The quantitative change in specific nutrients, secondary metabolites, defensive and antioxidant enzymes were measured at seedling stage of thethree alfalfa cultivars. The results showed that with the increase of thrips densities, the damage indices, SS, Pro, flavonoids, tannin and H2O2 in G9, G3 and 363 weresignificantly increased, but PPO and SOD significantly reduced, compared with CK. Furthermore, the tannin and lignin contents of G9 were significantly higher compared to 363, but SP content was significantly lower than G3 and H2O2 content whichwas furthersignificantly less compared to 363. Correlation analysis observed that the damage index of thethree alfalfa cultivars showed a significant positive association with SS, Pro, flavone, tannin, and H2O2 (P < 0.01), while damage index and DW, Chl (a, b, a + b), PPO and SOD showed a significant negative correlation (P < 0.01). Based on principal component comprehensive evaluation, the 5-thrips adults per branch were the critical inoculation threshold for G9 against thrips injury because the score was -0.048. These results revealed that thrips damage significantly increased the contents of SS, Pro, flavonoids, tannins and H2O2,as well as significantly declined the activities of PPO and SOD in the three cultivars (P<0.05), moreover, thrips-resistant G9 markedlyaccumulated lignin content, POD and CAT activity, inhibited Chl (a + b, b) and SP biosynthesis to resist thrips damage.

Population Density of Thrips tabaci Lindeman on Onion in relation to Palnting distances, Intercoropping Systems with Garlic Varities, and Yield

The present studies includes were conducted to study the effect of planting distances (5, 10 and 15 cm.), intercropping with onion plants and garlic varieties on the population of Thrips tabaci on onion plants during two successive seasons (2017 /2018 and 2018 / 2019) in Assiut Governorate, Egypt, using the two garlic varieties (Egyptian and Chinese). Results indicated that the three mentioned variables have significant effect on the population of the pest. The plant distances were the most significant factor, with the high numbers of thrips closest spacing (5 cm.) between plants. Intercropped garlic with onion showed that the garlic harbored lowest number of the pest whereas; in onion solo the density of pest is high compared with intercropped with garlic. Onion with garlic Egyptian variety is lower infested than the onion with garlic Chinese variety one. It was also noticed that the highest yield of onions was given when the distance between plants was (10 cm.) and loading onions with garlic resulted in a lower yield than onions grown separately during the two seasons. Keywords: Onion, garlic, planting distances, intercropping with garlic varieties, Thrips tabaci , population, yield.

Evaluating combinations of bioinsecticides and adjuvants for managing Thrips tabaci (thysanoptera: Thripidae) in onion production systems

Little is known about the performance of bioinsecticides in combination with adjuvants approved for organic onion production. To address this issue, two studies were conducted in 2018 and 2019: 1) combinations of four bioinsecticides (Isaria fumosorosea Apopka strain 97, azadirachtin + pyrethrins, azadirachtin, and spinosad) and three adjuvants (pinene polymers, potassium salts of fatty acids, and neem oil) in field trials in New York and Wisconsin, and 2) the same four bioinsecticides co-applied with neem oil as an adjuvant in field trials in New York. In both studies, spinosad was the most effective bioinsecticide, providing the largest reductions in thrips densities (26–85%) and feeding damage (56–69%) and the largest increases in total onion yield (10–26%) compared with the untreated control. Co-applications of spinosad with either neem oil or salts of fatty acids more effectively reduced thrips densities compared with co-applications of spinosad and pinene polymers; however, onion yield was similar regardless of the adjuvant used with spinosad. Isaria fumosorosea Apopka strain 97 and the premix of azadirachtin + pyrethrins did not control thrips. Implications of our results underscore the importance of evaluating the performance of insecticide and adjuvant combinations for optimizing pest management.

On collection of predatory thrips (Insecta: Thysanoptera) in wheat fields

Some thrips species are known as predators of eggs, exist as the inactive stages of mites, and can be tiny, especially phytophagous thrips. This study aimed at evaluating the population fluctuation and species diversity of predatory thrips in wheat fields of Eyvan county (Ilam province, Iran) in the year 2016. Thrips specimens were collected and identified by weekly sampling during wheat growth stages (from early April to late June). Wheat bushes were shaken on a white dish. Finally, microscopic slides were prepared and all samples were enumerated. The population fluctuation of predatory thrips was calculated. In this study, six species of predatory thrips belonging to three genera were identified. Amongst them, Aeolothrips intermedius Bagnall (family Aeolothripidae) was the dominant species in both irrigated and rainfed wheat fields accounting for 72.43% and 50.85% of all species, respectively. Biodiversity indices were calculated using the number of species and their relative abundance. Shannon diversity, Simpson’s, Margalef’’s and species richness indices were 1.76, 0.86, 1.25 and 1, respectively. The highest biodiversity was in rainfed fields and during the wheat flowering stage, and the highest Shannon-Wiener evenness index was also in rainfed fields and at the ripening stage. The richness of thrips in rainfed wheat fields during the stem elongation stage was higher than in other wheat stages. Correlation of the density of predatory thrips with temperature and humidity showed a significantly positive correlation with temperature.

Practical use of inoculative release of the predatory mite, &lt;i&gt;Amblyseius swirskii&lt;/i&gt; Athias-Henriot, against thrips on broad bean in open fields

The practical effect of the inoculative release of the predatory mite Amblyseius swirskii Athias-Henriot against thrips on broad bean was evaluated in commercial farmer fields. Experiments were conducted at six different fields from October to December in 2019 in Ibusuki City, Kagoshima, Japan. The dominant species of thrips was Thrips hawaiiensis（Morgan）. The population densities of thrips when A. swirskii was released were significantly lower throughout experiment and decreased by approximately 35% on average compared to the control （non-treatment） trials in the five fields. However, the predatory mites were not effective in one field. Differences in the densities of predatory mites on broad bean might affect the efficacy. Further research is required to improve the efficacy and success of biological control for broad bean.

The effectiveness of some pesticides in the control of thrips and red spider mites on strawberry plants

This study was carried out in a private farm in Wardan, Giza governorate in Egypt during 2019 season on strawberry plants. The first experiment aimed to evaluate the effectiveness of different commercial products in cultivated land including Solo 24% SC (Bifenazate), Arbus 12% SC (Chlorfenapyr + Emamectin benzoate) , Concor 24% SC (Spirodiclofen), Excellent 1.9% EC (Emamectin benzoate) , Top9 (Chitosan 0.1%) , Biomectin 5% EC (Abamectin) and Congest 15% CS (Abamectin + Imidacloprid) in reducing the population densities of two spotted spider mite, Tetranychus uriticae Koch. on strawberry plants. According to general mean percentage of reduction in population of T. uriticae, data showed insignificant differences among the seven tested compounds whereas the mortality percentages were 85.94 %, 82.18%, 81.4%, 79.36%, 78.14%, 77.94% and 75.9%, respectively. From these results; it’s clear that Solo compound is the most effective compound and Congest is the lowest one. The other compounds ranged between them in controlling T. uriticae under these experimental conditions. The second experiment evaluated the effectiveness of different formulations in the nursery including Radiant (Spinetoram 12% Sc), Super Rigo (Naphthyl acetic acid – Chitosan), Top9 and Berna Star (Glyceryl stearate 32%) in reducing the population densities of western flower thrips, Frankliniella occidentalis (Pergande) on strawberry plants. According to general mean percentage of reduction in population of F. occidentalis, data showed significant differences among the four compounds. These compounds could be divided into three groups. The first group contained Radiant compound showing high mortality (63.5%). The second group contained Super Rigo and Top9 compounds showing moderate effect (46.44% & 34.3%), respectively. The third group contained Berna Star compound showing least effect (28.36%). From these results; it’s clear that the chemical compound Radiant is the most effective while the natural compound Berna Star is the lowest in controlling F. occidentalis under these experimental conditions.

Phenology and description of a new species of Hoplothrips (Thysanoptera: Phlaeothripidae) in Mojave Desert leaf litter

A description and diagnosis are given for Hoplothrips cooperi sp. nov. collected from leaf litter beneath Chilopsis linearis (Cavanilles) Sweet (Bignoniaceae) shrubs in the Mojave Desert in southern Nevada. All adult males and most adult females are apterous, with macropters produced only in females. I examined the phenology of the species at a single locality during 27 November 2018 to 19 June 2019. Three generations were evident during winter and spring from the densities of larval and pupal instars. The timing and abundances of these generations appeared dependent on rainfall, consistent with thrips feeding on fungi growing on moist, dead leaves and stems. Most apterous adults and all macropterous females were collected during late spring when thrips densities and leaf-litter temperatures were highest. Hoplothrips cooperi appears to be the first species in the genus to be collected from leaf litter in the western U.S. and Mexico.

Challenges in integrated pest management: A case study of onion thrips and bacterial bulb rot in onion

Most agricultural production systems face challenges with multiple arthropods, plant pathogens and/or weed species, but few studies address the impact of multiple pests when developing integrated pest management programs. In onion production, onion thrips and bacterial bulb rot are primary constraints, and choice of onion cultivar, fertility regime and insecticide use may be important tactics to manage both. In a two-year study in New York, two independent field trials were conducted concurrently. The first experiment included either a moderately thrips-resistant cultivar (‘Avalon’) or a thrips-susceptible cultivar (‘Bradley’), multiple nitrogen rates (0, 67, 84, 118, and 151 kg/ha) and either a season-long, action threshold-based insecticide program or no insecticide program (20 treatments total). The second experiment included the same cultivars and insecticide programs but evaluated phosphorous rates (0, 56, 112, and 168 kg/ha) (16 treatments total). In both trials and years, ‘Avalon’ experienced lower thrips densities, but suffered 58% more bacterial rot, which reduced onion yields overall by 9%. Nitrogen and phosphorus fertilizer had limited impact on onion thrips, bacterial rot, and onion yield. Although, higher rates of nitrogen fertilizer increased bacterial bulb rot in 2017. In both years, low rates of fertilizer (67 kg/ha N or 56 kg/ha P) produced statistically similar yields to plants supplemented with the highest rates of fertilizer. Insecticide use reduced thrips densities and increased bulb yield in both years but did not consistently reduce bacterial bulb rot. Therefore, growers can optimize onion production by reducing rates of fertilizer and using an action-threshold based insecticide program. Furthermore, our results indicate that IPM programs should be evaluated to consider multiple biotic constraints simultaneously within an agricultural production system as IPM tactics can be counterproductive.

Evaluation of Tillage, At-Planting Treatment, and Nematicide on Tobacco Thrips (Thysanoptera: Thripidae) and Reniform Nematode (Tylenchida: Hoplolamidae) Management in Cotton

There are numerous early-season pests of cotton, Gossypium hirsutum L., that are economically important, including tobacco thrips, Frankliniella fusca (Hinds), and reniform nematode, Rotylenchulus reniformis (Linford &amp; Oliveira). Both of these species have the potential to reduce plant growth and delay crop maturity, ultimately resulting in reduced yields. A field study was conducted during 2015 and 2016 to evaluate the influence of tillage, at-planting insecticide treatment, and nematicide treatment on pest management, cotton development, and yield. Treatment factors consisted of two levels of tillage (no-tillage and conventional tillage); seven levels of at-planting insecticide treatments (imidacloprid, imidacloprid plus thiodicarb, thiamethoxam, thiamethoxam plus abamectin, acephate plus terbufos, aldicarb, and an untreated control); and two levels of nematicide (no nematicide and 1,3-dichloropropene). There were no significant interactions between tillage, at-planting insecticide treatment, or nematicide for any parameters nor was there a difference in the main effect of nematicide on thrips control or damage. The main effects of tillage and at-planting insecticide treatment impacted thrips densities and damage. The no-tillage treatments and aldicarb in-furrow or acephate seed treatment plus terbufos in-furrow significantly reduced thrips populations. Early-season plant response was impacted by tillage and at-planting insecticide treatment; however, that did not result in significant yield differences. In regard to nematicide treatment, the use of 1,3-dichloropropene resulted in lower yields than the untreated.

Distribution Pattern of Thrips (Thysanoptera: Thripidae) and Tomato Chlorotic Spot Virus in South Florida Tomato Fields.

Tomato chlorotic spot virus (TCSV) is an orthotospovirus that causes a devastating disease in tomato (Lycopersicon esculentum Miller). TCSV emerged recently in South Florida. Studies were conducted in three commercial tomato fields in Miami-Dade County, Florida during the vegetable-growing seasons from October to April in 2015 through 2017. Each year, data were collected at 3, 6, and 9 wk after transplanting at various distances from the edges of each fields. Based on 3 yr total samples, three species of thrips were commonly observed melon thrips, Thrips palmi Karny (62.16 ± 0.79%), being the most abundant species followed by common blossom thrips, Frankliniella schultzei Trybom (21.55 ± 0.66%), and western flower thrips, Frankliniella occidentalis (Pergande) (16.26 ± 0.61%). Abundance of all thrips and TCSV infected plants was high at the edge of a tomato field 3 wk after transplanting with significantly fewer infected plants toward the center of the field. The distribution patterns of thrips and TCSV in various fields were mostly regular and aggregated across the sampling dates during the study period. Abundance of TCSV symptomatic plants and thrips species was high at the edge of the field and increased over time. The number of samples required to accurately determine population density of thrips was calculated by using three precision levels (0.10, 0.20, 0.30) at three predetermined densities of thrips (0.10, 0.20, and 0.40 per sample). This information will provide guidelines to growers, crop protection personnel, agricultural scouts, and researchers to develop a sustainable thrips and tospovirus management program.

Evaluation of Seed Treatment, Herbicide, and Nematicide on Tobacco Thrips (Thysanoptera: Thripdae) and Reniform Nematode (Tylenchida: Hoplolaimidae) Control

Numerous pests infest cotton early in the season. Some economically important are Palmer amaranth, Amaranthus palmeri (S. Wats); tobacco thrips, Frankliniella fusca (Hinds); and reniform nematode, Rotylenchulus reniformis (Linford and Oliveira). Thrips and weed management are essential to prevent delayed maturity and reduced crop yield. A field study was conducted during 2015 and 2016 to evaluate the influence of insecticide seed treatment, herbicide, and nematicide on tobacco thrips and reniform nematode control, as well as the impact on cotton growth, development, and yield. Treatments consisted of insecticide seed treatment (insecticide seed treatment and fungicide only), herbicide application (S-metolachlor, glufosinate, S-metolachlor plus glufosinate, and no herbicide), and nematicide application (1, 3-dichloropropene and no nematicide). There were no significant interactions between insecticide seed treatment, herbicide, and nematicide for any parameter. Nor were there any interactions in respect to nematode densities, thrips densities, thrips injury, herbicide injury, or plant biomass. Nematode densities were reduced with the use of 1,3-dichloropropene when sampled at first square and post-harvest. Thrips densities and injury were reduced at the 1- to 2-leaf stage sample timing with an insecticide seed treatment, but not at the 3- to 4-leaf stage sample timing. Herbicide injury was the greatest following S-metolachlor plus glufosinate applications (&lt; 12%). A significant interaction between nematicide and insecticide seed treatment was observed for cotton yield, where the use of 1,3-dichloropropene and the insecticide seed treatment resulted in greater yields than all other treatments.

Effect of barrier crops as a management tool against Thrips tabaci in onion ecosystem

Impact of barrier crops on the management of Thrips tabaci was studied for two consecutive years. Wheat, mustard and fennel were grown as border crops of onion crop and were compared to imidacloprid treated onion and untreated sole onion crops. Wheat barrier crop (WBC) gave significant result followed by mustard (MBC) and fennel barrier crops (FBC) in relation to reduction in the density of onion thrips. Dispersal of T. tabaci was prevented by presence of vertically tall wheat plants during both the years. The incidence of T. tabaci was variably influenced by abiotic factors. Weather parameters showed positive correlation with thrips population in all the treatments except relative humidity. A non-significant correlation was found between rainfall and thrips density. Yield was significantly higher in WBC than other barrier crops and the control. It was 11.33 and 12.63 t/ha with 2.09 and 3.34 t/ha yield of wheat in 1st and 2nd year, respectively. Wheat as a barrier crop in onion ecosystem managed T. tabaci.

Avaliação de inseticidas para o controle de Thrips tabaci (Lindeman, 1889) (Thysanoptera: Thripidae) em campo, na cultura da cebola

The efficacy of 14 different insecticides was tested for the control of onion thrips Thrips tabaci (Lindeman, 1889) on onion in Itajaí Valley, SC during 2018. The insecticides were sprayed six times at intervals of about seven days, we evaluated the number of nymph of thrips per plant 48 hours after spray, visually rated for thrips damage at 96 DAT and total and commercial onion bulb production. Significant diferences were observed between various insecticides evaluated. The treatments formetanate hydrochloride, spinetoram and abamectin proved the best thrips control, less thrips damage and good total and commercial productivity. The insecticide profenofos + cypermethrin exhibited reduction of thrips nymph and better total and comercial production comparing control however not reduced thrips damages. The insecticides thiacloprid, thiamethoxam + lambda-cyhalotrin, and Imidacloprid reduced the thrips density but had similar results for thrips damages and onion bulb production comparing with control, excepting total productivity for the neonicotinoids thiacloprid and and Imidacloprid.

Experienced males recognise and avoid mating with non-virgin females in the western flower thrips.

The western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) is a major insect pest on a wide range of crops throughout the world. There are several unexplained aspects of the mating behaviour, particularly in relation to male-male competition and mate choice. The objectives of the study were to test whether males can detect the mating status of females and whether males avoid mating with previously mated females. Experiments involved either ‘experienced’ adults taken from a laboratory culture, which had been exposed to high densities of thrips, or virgin adults reared individually. Experienced males mated readily with virgin females, but avoided mating with experienced females. Virgin males showed much less discrimination between females. Avoidance of mating with experienced females is likely to be widespread because it occurred in populations from both the United Kingdom and Kenya. Experienced males also mated with dead virgin females, but avoided mating with dead experienced females, which ruled out the possibility that behavioural differences between the females were responsible. To test whether males could detect whether or not females had mated, virgin females of the same age from the same cohort were either mated once or not mated. Experienced males mated with the dead females that were virgin and avoided mating with the dead females that differed only in that they had mated once shortly before. This showed that males recognise whether or not a female has mated and avoid mating with previously mated females. This avoidance by males suggests that mated females are not usually subjected to high levels of male harassment. The most likely explanation of the avoidance is that males produce an antiaphrodisiac pheromone that is applied to females during mating.