Total Number Of Thrips Research Articles

Susceptibility of spring wheat to infestation with wheat blossom midges and thrips

Susceptibility of spring wheat to infestation with wheat blossom midges (WBM) and thrips was studied in Central Germany in the two seasons, 2008 and 2009. WBM Sitodiplosis mosellana, Contarinia tritici and the thrips species Limothrips denticornis and L. cerealium are among the major pests of wheat ears. Pheromone traps were used for surveying S. mosellana adults. Ear-infestations in the wheat varieties Triso (high quality in Germany) and Sakha 93 (resistant to drought in Egypt) were evaluated by counting insects at flowering stage (GS 65) and the milk-ripe stage (GS 73). Migrating WBM larvae were evaluated using water traps. In the pheromone traps, density of S. mosellana adults started high and then the population steadily declined until the end of the season. There was no significant difference in the total number of thrips and WBM larvae between varieties at GS 65 in either year, while differences between varieties at GS 73 were significant. Thrips and WBM larvae numbers were significantly higher in Triso than Sakha 93 in 2008 and 2009. The infested ears were positively correlated with WBM counts in both varieties. Numbers of migrated yellow midge larvae were higher in 2008, but lower in 2009 than orange midge. Yield was higher in Triso than Sakha 93 in both seasons.

The diurnal flight activity and influential factors of Frankliniella occidentalis in the greenhouse

Abstract The daily flight activity of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) was examined using color, yellow‐light and chemical attractant traps in a cucumber greenhouse and under controlled laboratory conditions. In the greenhouse, flying thrips were most abundant between hours 08:00–10:00, declined at mid‐day, and then slightly increased during hours 14:00–16:00; however they decreased to a very low level at 18:00. The use of light traps showed no thrip flight activity during the night. The total number of thrips that flew onto cards on rainy or cloudy days was higher than that on sunny days. We reconfirmed that traps treated with attractant attracted 4.0–9.4 times more thrip than the untreated traps. Under laboratory controlled conditions, thrip flight activity was highest under light intensity between 4 000 and 6 000 lux, air temperature of 28°C, and RH of 70%. In addition, starved thrips flew more readily than non‐starved thrips.

Spatial Distribution of Thrips in Greenhouse Cucumber and Development of a Fixed-Precision Sampling Plan for Estimating Population Density

Dispersion patterns of phytophagous thrips (Thysanoptera: Thripidae) were determined for greenhouse cucumber, Cucumis sativus L., in Cheju-do, Korea, during 1995 and 1996. Thrips populations were sampled using leaf sample, yellow sticky trap and visual estimate concurrently on each sampling date. Frankliniella occidentalis (Pergande) was the most dominant thrips species, accounting 92% of all specimens collected from leaf samples and yellow sticky traps. Dispersion indices generated by Taylor's power law and Iwao's patchiness regression were compared. Generally, Taylor's power law provided better description of mean-variance relationship than did Iwao's patchiness regression with exception of the data from the sticky trap. Slopes and intercepts of Taylor's power law from leaf sample and visual estimate did not differ among thrips species and surveyed greenhouses. A fixed-precision-level of sequential sampling plan was developed using Taylor's power law parameters generated from total number of thrips in leaf sample and visual estimate. This sampling plan for visual estimate was tested with sequential resampling simulation using 4 independent data sets. Resampling simulation analysis demonstrated that actual D values were always less than desired D values of 0.20, 0.25 and 0.30.

Eliminating Thrips in Microshoot Cultures

Two insecticides, acephate or azadirachtin, were added to tissue culture media to determine their effectiveness in controlling onion thrips (Thrips tabaci Lindeman.) and to determine if these insecticides could damage the plant shoot cultures. To test for insecticide phytotoxicity, microshoots from European birch (Betula pendula), American elm (Ulmus americana), `Pink Arola' chrysanthemum (Dendranthema grandiflora), `America' rhododendron (Rhododendron catawbiense), `Golden Emblem' rose (Rosa hybrida), and `Gala' apple (Malus domestica) were placed in 130-ml baby food jars containing 25 ml of medium supplemented with 6.5, 13, or 26 mg/l Orthene® (contained acephate) or 0.55, 1.1, or 2.2 ml/l Azatin® (contained azadirachtin). Control jars lacked insecticide. To test for thrips control, 13 mg/l Orthene® or 0.55 ml/l Azatin® was added to Murashige and Skoog medium, and 10 thrips were placed on `Gala' apple microshoots in each jar. Jars were sealed with plastic wrap. In both studies, microshoot dry weight and heights were determined. In the second study, the total number of thrips per jar was also determined 3 weeks after inoculation. Microshoots on Orthene®-treated media lacked phytotoxicity symptoms, regardless of the concentration used. In contrast, Azatin® hindered plant growth, decreasing shoot height or dry weight by up to 85% depending on the species. Both insecticides prevented thrips populations from increasing, since less than 10 thrips were found in jars with insecticide-treated medium. Control jars, however, contained an average of almost 70 thrips per jar. This study demonstrated that both Orthene® and Azatin® were effective for eradicating thrips from plant tissue cultures, but Orthene® should probably be used because Azatin® was phytotoxic to all species tested.

Evaluation of Insecticides for Thrips Control on Seedling Onions, 1995

Abstract Insecticides were evaluated for control of onion thrips in a commercial field of ‘Crusader’ seed onions planted 11 Jul on 36 inch beds in double rows 14 inch apart near Madras, Oregon. The 9 ft x 20 ft plots were replicated 3 times in a RCB design. Insecticides were applied on 17 Sept using TeeJet 8002 nozzles on a 9 ft CO2 pressurized, hand-held, boom sprayer at 40 psi and 20 gal/acre of water. Silgard at the rate of 2 pt/100 gal was applied in combination with all insecticides. Efficacy was determined by inspecting 15 plants in the middle rows and recording total number of thrips observed. Counts were made 14 Sept prior to application and 1, 6, and 10 DAT on 18, 23 and 27 Sept.

Insect Control on Staked Tomatoes, 1995

Abstract Six-week-old transplants were set on 15 June at the Mountain Horticultural Crops Research Station, Fletcher, NC. Plants were set 2 ft apart within 20 ft rows and rows were on 10 ft centers. Single-row plots were arranged in a RCB design with four replications. Materials were applied on 21 and 31 July, 7, 14, 21, and 30 Aug and 6, 14 and 21 Sep with a tractor-mounted boom sprayer delivering 50-100 gpa (gpa increased as plants grew) through 7 hollow cone nozzles per row (three nozzles on each side and one overhead). Those treatments which were targeted specifically at lepidopterous (LEPS) pests (i.e., Biobit HP, Biobit HP + F-1512, Biobit XL, Dipel 2X, and Confirm 70W) all received Provado 1.6F at 3.75 oz/acre on 31 July, 14 and 30 Aug and 14 Sep for PA and SB control. PA populations were monitored on 11, 20 and 25 July, 1, 11, 16 and 22 Aug by observing 10 leaves (3rd most recently expanded leaf) per treatment and recording the number infested with ≥ 1 apterous aphid. Thrips were monitored on 20 July by counting the total number of thrips (FT, WFT, OT) on 10 flowers per treatment (40 flowers total per 4 reps). Fruit was harvested on 16, 21 and 28 Aug and 5, 11, 18 and 25 Sep and those damaged by LEPS, SB and thrips were recorded. All data were analyzed using a two-way ANOVA, and means were separated by using LSD (P=0.05).

Spatial Distribution and Sampling Procedures for Frankliniella spp. (Thysanoptera: Thripidae) in Staked Tomato

Phytophagous thrips were sampled in commercial tomato, Lycopersicum esculentum L., fields in western North Carolina during a 3-yr period from 1990 to 1992. Tomato flowers were collected to sample thrips and evaluate 3 different sampling units (2, 5, and 10 flowers) for their relative net precision. Flower thrips, Frankliniella tritici (Fitch), and western flower thrips, frankliniella occidentalis (Pergande), were the dominant species collected, accounting for 96% of all specimens. Relative net precision values indicated that a 10-flower unit was more precise and cost-efficient than either the 2- or 5-flower unit. Frequency data collected from the 10-flower unit were described by the negative binomial distribution. Both F. occidentalis and F. tritici exhibited an aggregated distribution in tomato fields. Taylor power law provided a better fit to the data than Iwao patchiness regression. Slopes and intercepts of Taylor power law did not differ among thrips species or total thrips. A fixed-precision-level sequential sampling plan was developed using the parameters of Taylor power law generated from total number of thrips in a 10-flower sampling unit. The resulting sampling plan was tested with sequential sampling bootstrap simulations (n = 500) using 11 independent data sets for the validation. Bootstrap simulation over a range of densities demonstrated that actual Do values at Do = 0.30 averaged <0.26 in every case.

Efficacy of Insecticides Against Thrips on Dendrobium, Hi, 1994

Abstract Tests were conducted from 14 Jul through 8 Sep 1994 on 8 year old orchid plants at a commercial dendrobium farm in Kailua-Kona. Plants were growing in 1.3 cm crushed basaltic rock under 30% polypropylene shade using standard cultural practices. Experimental plots measured 40 ft2 with 58 plants per plot arranged in a RCB with four blocks. Four weekly applications of insecticides were applied beginning 14 Jul and ending 4 Aug. A spreader-sticker (Ad-here, J. R. Simplot, Lanthrop, CA) was added to all foliar treatments, including the control, at a rate of 0.5 ml per liter solution. Insecticides were applied at 1,345 liters/ha using a backpack sprayer (Solo Inc., Newport News, VA) equipped with an 8004 Teejet nozzle (Spraying systems Co. Wheaton, IL) at 276 KPa. The control was sprayed with water. Treatment efficacy was evaluated by randomly harvesting 5 inflorescences weekly from each block. Blossoms were removed from the inflorescences, counted, and placed in Berlese funnels heated with a 60 watt incandescent light bulb. Thrips were collected in an 8:2:1:1 solution of ethanol, distilled H20, acetic acid and glycerin, and the number of nymphs and adults counted. Because the number of blossoms per inflorescences varied, thrips counts were adjusted to the number of thrips per blossom by dividing the total number of thrips recovered by the total number of blossoms. Data were transformed to log,0(x + 1) and analyzed by ANOVA.

Field Evaluation of Traps for Monitoring Emergence of Pear Thrips (Thysanoptera: Thripidae)

Black and white plastic cylindrical traps with diameters of 7.6-20.3 cm and a cone-shaped trap with a base diameter of 45.7 cm were tested in three forest stands for their efficiency in monitoring emergence of pear thrips, Taeniothrips inconsequens (Uzel), from soil. The total number of thrips and thrips per square centimeter collected in black and white traps of the same diameter did not differ significantly. The mean number of thrips collected per trap (catches from black and white traps combined) ranged from 1.1 ± 0.28 to 46.8 ± 20.75, and significantly more were collected in the 15.2-,20.3-, and 45.7-cm traps than in the 7.6- and 10.2-cm traps. Significantly more thrips per square centimeter were caught in the 15.2-cm trap than in the 7.6- and 45.7-cm traps, except in one stand with a very low thrips population, where thrips catches among trap types did not differ significantly. The 7.6-cm trap was the least expensive to construct and required less time for monitoring than the other plastic traps.

Insecticide Efficacy Against Western Flower Thrips, Georgia, 1985

Abstract Six insecticides were tested against Western flower thrips on tomato bedding plants. All plants were moderately infested with thrips, with the species composition approximately 90% Frankliniella occidentalis and 10% Echinothrips americanus Morgan. The experimental design was a randomized complete block with 3 plants per treatment plot and each plot replicated 4 times. All materials were applied with a compressed air sprayer, 8003 nozzle, at 30-35 psi until runoff. Pretreatment counts were made the same day as pesticide application. After spraying, the plants were placed on greenhouse benches. Efficacy was based on the total number of thrips (adult and immature) found on each plant with the aid of a magnifying lens.

Varietial Resistance in Onions to Thrips123

The onion cultivar ‘Nebuka’ had 48, 72, and 67% fewer adult onion thrips, Thrips tabaci Lindeman, caught on sticky-card traps than cultivars ‘Texas Early Grano 502’ and ‘951,’ and ‘Creole,’ respectively. Number of larval thrips per plant was a better indicator of hostplant resistance than number of adults on sticky-cards or taken from foliage, or the total number of thrips per plant. Damage rating for Nebuka was 5.0 compared with 9.0, 8.9, and 8.5 for Texas Early Grano 502, Texas Early Grano 951, and Creole respectively. Morphological characters of Nebuka described over 40 yr ago as factors regulating thrips populations in onions were still effective in reducing damage by thrips.