جستجوی مقالات مرتبط با کلیدواژه « Onion thrips » در نشریات گروه « کشاورزی »

The onion thrips, Thrips tabaci Lindeman, one of the most important pests of vegetables, ornamentals and leafy crops, is widely distributed worldwide. Therefore, the study of factors contributing to the spread of this insect in agricultural ecosystems is of great importance. Considering the physiological conditions of this pest, wind is considered one of the most important factors for its spread. In this study, we investigated the effects of wind conditions on the spread of T. tabaci in Golestan province in 2021. We selected 48 cotton fields (at the cotyledon stage) in Golestan province and collected data on the relative population density of T. tabaci over a period from 10.03.1399 to 04.04.1399 (three times per week). The relative population density of thrips in each monitoring field (with a minimum size of one hectare) was estimated using the "shaking method" by placing white paper or plastic trays under randomly selected cotton plants, ensuring that they completely covered the lower leaves. We then counted the average number of thrips that fell on the white surface per plant and reported the results per hectare. Wind speed and direction during this period were analyzed using data from eight weather stations and wind rose diagrams were created. The data processing and wind statistics as well as the creation of the wind rose diagrams were carried out using WRPLOT software.  The average population density of T. tabaci in Golestan province during the specified period was 38.5 thrips per plant, with all stages recorded. No statistically significant difference was found between the districts of Golestan province in terms of relative population density of thrips. The percentage of frequency of windlessness (less than 0.54 m/s) was 69.86 to 84.48%. Spatial autocorrelation analysis (Moran's I) was used to identify hotspots (areas with a high probability of occurrence) of T. tabaci. The overall Moran's I values during the monitoring period (I = 0.35, p-value = 0.0174) indicated a random distribution of Thrips tabaci population density data collected in the fields. The map of relative density of T. tabaci in the cotton fields using inverse distance weighting method showed infestation centers in Gorgan, Kordkuy, Bandar Gaz and Aliabad regions.  Based on the results, it is possible to predict the dispersal patterns of onion thrips by obtaining information about the prevailing winds, which in this study came mainly from the west. By predicting the starting points of the infestation, certain control measures, such as the use of sticky traps along the prevailing wind directions, can be recommended to farmers.

Camelina, Camelina sativa (L.) Crantz (Brassicaceae) is an oilseed plant that was imported to Iran in 2015. Camelina is a cold-tolerant oilseed crop with minimal input requirements. In this study, the population density of Thrips tabaci Lindeman and its effect on the yield of different lines of camelina were investigated under field conditions. In this regard, 136 lines of camelina cultivated in the farm and for sampling, each plant was considered as a sampling unit and the number of thrips was counted on each plant after tapping. The number of healthy and injured capsules and seeds were also counted in each line with three replications. The results showed that yield decreased with increasing percentage of injured capsules. In addition, the percentage of damaged seeds was negatively correlated with the yield of camelina lines and the percentage of injured capsules was positively correlated with the percentage of damaged seeds. The results of linear regression showed that the relationship between thrips population density and yield and percentage of damaged seeds was not significant, while a positive and significant relationship was observed between thrips population density and percentage of injured capsules, meaning that with increasing thrips density, percentage of injured capsules increased, as well. Based on the findings, line 54 was recognized as the most resistant line against T. tabaci which was a semi-sensitive, resistant and tolerant line in term of antixenosis, antibiosis and tolerance mechanisms, respectively.

The abundance of the western flower thrips, Frankliniella occidentalis, along with the onion thrips, Thrips tabaci, in the greenhouse of tomato, cucumber, Alstroemeria, Rose and Gerbera were determined by weekly sampling from November 2018 to May 2019 in Isfahan districts. The competition ability of these two species on cucumber was evaluated by comparing their fertility-life table parameters at two different temperatures and also by measuring the density of each species over time with different initial densities of both species. The results showed that the population of the western flower thrips was always higher than onion thrips in greenhouses. The fertility- life table parameters showed that an increase in temperature leads to increase the western flower thrips’s population. At 25 ° C, the intrinsic rate of increase (0.17 day-1) and the net reproductive rate (51 nymphs) of onion thrips were higher than the western flower thrips, and at 27 ° C the western flower thrips had higher intrinsic rate of increase (0.18 day-1) and net reproductive rate (45 nymphs) than those of onion thrips. Since the value of intra-specific competition for onion thrips (0.34) and western flower thrips were 0.34 and 0.14, respectively. The onion thrips population growth is more affected by intraspecies competition than western flower thrips and so the western flower thrips is more successful in interspecific competition than onion thrips.

Onion thrips, Thrips tabaci is the most well-known and most common polyphagous thrips worldwide and is one of the major pests of legume fields, causing significant damage to various crops each year. In this study the life table parameters of onion thrips was studied on lentil and chickpea plants at laboratory conditions (25 ± 1°C, 70 ± 5% RH and 16: 8 h L: D). The total life cycle fromegg to adult and the mean adult longevity on lentil and chickpea plants were calculated as 13.81 and 15.81 days, and 13.44 and 13.91 days respectively. The females laid 43.90 and 24.84 eggs on average. The immature mortality was 10.37 and 19.78 on lentil and chickpea, respectively. The net reproductive rate (R0) was 39.51 and 20.22, and the intrinsic rate of increase (rm) was 0.185 and 0.133 respectively. The finite rate of increase (λ) was 1.20 and 1.14. However, mean generation time (T) and doubling time (DT) on two host plants was calculated as 19.81, 22.47 and 3.73, 5.18 day. The results showed that all of the life table parameters of T. tabaci on lentil plant were statistically significantly different from chickpea plant. According to these results, it seems that lentil is a more suitable host plant for onion thrips.

Alfalfa (Medicago sativa L.), also called lucerne, is the most important forage which cultivated in the most parts of the world. The main source of alfalfa is Southwest Asia, especially Iran. Alfalfa is a perennial forage legume which normally lives four to eight years, but can live more than 20 years, depending on type of its variety and climate. In the most regions, alfalfa is generally harvested three to four times and can be done up to 12 times per year. Many types of insects are found in alfalfa fields including beneficial, and harmful insects, which feed on the leaves, flowers, root and seeds. Amongst them, thrips are a group of insects belonging to the order Thysanoptera. Thrips have been considered in most areas. Different species of thrips have been recorded on alfalfa fields in western Iran i.e. Odontothrips confosus Priesner, Odontothrips iranensis Mirab-balou et Chen, Thrips tabaci, Frankliniella intonsa (Trybom), F. pallida (Uzel), Haplothrips reuteri (Karny) and Neohydatothrips gracilicornis (Williams).Therefore, it is critical to determine the biodiversity status of the thrips in order to manage its population.

To study the biodiversity of thrips species in different alfalfa cuttings, the sampling was weekly carried out during April to the middle of September 2016 in alfalfa fields (1-year-old, 3-years-old and 4-year-old) of Eyvan city (Ilam province), the west of Iran. The specimens were collected using shaking alfalfa plants in a white tray and transferred them to vials containing 75% ethanol. After transferring to the laboratory, all thrips specimens were mounted onto slides, and identified at the species level. The dominant thrips species were determined and biodiversity of thrips species in different alfalfa cuttings was calculated by biodiversity indices i.e. Shannon-Wiener, Simpson, Margalef and Evenness Shannon.

In the present study, 10 thrips species belonging to six genera and four different families were collected and identified from alfalfa fields. Among the collected species, the highest and the lowest frequency was obtained for Thrips tabaci (59.12%) and Tenothrips frici (0.24%), respectively. According to the calculations, the Shannon-Wiener, Simpson, Margalef and Evenness Shannon indices in 1-year-old alfalfa field were 2.71 ± 0.04, 0.92 ± 0.04, 3.49 ± 0.02 and 0.89 ± 0.01, in 3-year-old alfalfa field were 2.26 ± 0.09, 0.88 ± 0.009, 2.58 ± 0.18 and 0.91 ± 0.006, and in 4-year-old alfalfa field were 2.09 ± 0.14, 0.85 ± 0.01, 2.31 ± 0.29 and 0.92 ± 0.01, respectively. The results showed that the Shannon-Weiner, Simpson and Margalef indices of thrips species in 1-year-old alfalfa field were significantly higher than the 3 and 4-year-old alfalfa, however, the Evenness Shannon in 4-years-old alfalfa field was more than 1-year-old and 3-years-old alfalfa fields, this difference was not significant.

In this study, Shannon-Wiener index values varied between at least 2.09 in a 4-year-old alfalfa and a maximum of 2.71 in a 1-year-old alfalfa fields. The range of Shannon-Weiner index variables from 0 –5 and typically from 1.5 - 3.5. Lower values of this range indicates the presence of tension in the environment and instability, and more than it showed an increasing the biodiversity of the area. These values are good in comparison to the range of Shannon-Weiner index variables, which are generally between 1.5 and 3 in their sources. As the age of the plant raises, the amount of food decreases, so, insects less likely tend to establish on the host plants, and their variety will be reduced. Thrips tabaci is one of the most important pests with more than 300 host plants in the world. Considering that in the present study T. tabaci is a dominant species in the alfalfa fields, its infestation level should be managed correctly with respect to control method.

In order to study the population fluctuations and spatial distribution of onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae) in alfalfa fields of Eyvan city (Ilam province), sampling were done weekly in different growth stages of alfalfa from the beginning of April to late September 2017. The results of population fluctuations showed that the highest population of adult and immature thrips stages were average 6.20 ± 0.85 and 1.35 ± 0.44 in 20 plants in August and September, during the 3th cutting of alfalfa. The study of the relationship between the population dynamics of adult and immature stages with temperature showed that there was a significant and positive correlation between population changes and temperature. Based on Taylor’s power law, the spatial distribution for both adult and immature stages was randomized, but the total stages were aggregated. Whereas, based on Iwao's patchiness, regression between Log S2 and Log m in immature stage was not statistically significant (P> 0.05). The spatial distribution pattern of adult stages was randomized and for both adult and immature stages was aggregated. The parameters derived from population fluctuations and the spatial distribution pattern of this species can be used in the sampling program and estimates of population density of this pest in alfalfa fields.

Onion thrips, Thrips tabaci Lindeman, is one of the most common and important pests of agricultural products including eggplant. In present study, we investigated the mechanism of antixenosis, trichomes density and chlorophyll content of 10 eggplant genotypes (Black beauty, Blacky, Yalda, Lady, Linda, Lyma, Kyme, Borazjan, Siah-Mashhad and Mahali-Zabol) to the thrips in festationin a selection test . Experiments were performed in a greenhouse at 25 ±1°C, 65 ± 5 RH and 16L: 8D photoperiod. Total protein of the cultivars was isolated and electrophoresed using SDS-PAGE to determine the protein-electrophoresis pattern and its relation to the quantity of attracted thrips. Protein-electrophoresis showed differences in the number and type of the protein bands which are related to the variation among the cultivars in which the thrips-resistant cultivars can be used in the inbreeding programs. The genotypes were significantly different in terms of trichome densities and chlorophyll content as well as thrips-mediated damage percentage. There was no significant correlation between morphological attributions and molecular data. We believe that Lima and Linda genotypes, with highest genetic distance (0.454), can be successfully used in cross breeding programs, although complementary tests are required to improve the efficiency of the programs.

Formulation of blastospores of entomopathogenic fungi may help to overcome unfavorable climatic conditions and may increase their effectiveness. In the present study, different products of wettable powder of blastospores were prepared for two isolates of Beauveria bassiana and were stored at two different temperature regimes, refrigerator (4±1°C) and laboratory (24±3°C) conditions. After storage durations (24 hours and 30 days), their effects were investigated against second instar larvae of the onion thrips. Results indicated that mortality percent of thrips larvae in blastospore's treatments maintained in laboratory (BML), blastospore's treatments maintained in refrigerator (BMR), new formulated blastospore (NFB) and new blastospore )NB) in 108 spore/ml concentration were 66, 89.4, 92.7 & 91% in B. bassiana EUT105 and 70, 93, 89.8 & 91 % in B. bassiana EUT116, respectively. These results indicated positive effects of storing at low temperature on preserving high viability in treatments maintained in refrigerator than those maintained in the laboratory. The results of this study can be valuable base for research on increasing stability and efficacy of fungal spores, changing or replacement of carrier ingredients in our country.

Aggregation response of the predatory bug Orius niger (Wolff) at different densities (5, 10, 20, 30, 40 and 50) of the second instar nymphs of Thrips tabaci Lind. was examined on a cucumber leaf disc as a patch. The number of predatory bugs and their allocated time per patch was recorded. The index (µ), in Hassell & May, at all densities of the predator (1, 2, 4, 8, 16 and 32) appeared greater than zero and, was indicative of its tendency to aggregate in the patches where a higher density of prey occurred. The percentage time spent by the predatory bug at different patch densities of T. tabaci showed that it allocated more time in patches with higher densities of prey.