Predatory Thrips Research Articles

Functional response of predatory thrips to two-spotted spider mite – influence of pesticides

A leaf disc bioassay was used to investigate the effects of abamectin and fenpropathrin on the functional response of an acarophagous thrips, Scolothrips longicornis Priesner, to eggs of Tetranychus urticae Koch at 25 ± 1°C, 60 ± 10% RH, 16:8 h (L:D). The type of the functional response differed depending on the types and doses of the pesticides used. A type II functional response was found in all pesticide-dose combinations except for females exposed to a half-labelled dose of fenpropathrin, in which a type III functional response was observed. For type II functional responses, the search rates were similar to those found in the control treatments irrespective of predator sex, pesticide and pesticide dose. No differences in handling times across treatments were observed for males but handling times were longer for females, irrespective of pesticide and dose, compared to the control treatment. The theoretical maximum number of prey attacked by the thrips was 49.67 and 23.67 eggs per day for females and males, respectively; both maxima were attained in the control treatment. These values were reduced for males exposed to full doses of either pesticide and for females exposed to both half and full doses of either pesticide. These findings suggest that the efficacy of integrated management programmes for T. urticae involving the application of S. longicornis could be decreased by application of pesticides such as fenpropathrin and abamectin, which are often used to control pests in greenhouse and field crops.

Behavior of Montandoniola confusa Streito & Matocq (Hemiptera: Anthocoridae) preying upon gall-forming thrips Gynaikothrips ficorum Marchal (Thysanoptera: Phlaeothripidae)

The gall-forming thrips Gynaikothrips ficorum Marchal (Thysanoptera: Phlaeothripidae) is recorded in all regions where its host plant, Ficus microcarpa (Marchal) (Moraceae), has been cultivated as an urban and interior landscape plant species, including potted plants and bonsai. Similarly, the thrips predator Montandoniola confusa Streito & Matocq (Hemiptera: Anthocoridae) has generally followed the prey distribution. The gall induced by thrips degrades the plant foliage, and the thrips themselves can be annoying for people both outdoors and indoors. The galls, however, create a microcosm with all developmental stages of the thrips and its predator. In this study we present the first records of M. confusa in South America, document the species’ widespread concomitant occurrence across Brazil, and report our studies of three aspects of M. confusa predation upon the eggs, larvae/prepupae, and adults of G. ficorum thrips: (i) functional response of the predator adult female as a function of different densities of thrips eggs, larvae/prepupae and adults separately: (ii) predation on eggs by adult M. confusa with adult thrips present in the gall; and (iii) adult M. confusa prey preferences when all thrips stages occurred simultaneously in the gall. For all three thrips life stages tested, the predator exhibited a type II functional response. Despite the availability of different life stages in the gall, M. confusa adults are capable of preying upon all life stages of G. ficorum, predation was preferentially on thrips eggs, with an estimated ∼10-fold greater predation on eggs compared to larvae/prepupae and adult thrips. Egg predation was unaffected by the presence of defensive adult thrips in the gall under low densities (<30 eggs/gall) but when egg densities were greater than 30 eggs/gall, it was reduced when adult thrips were present. However, the relative number of thrips adults per gall did not statistically change the outcome.

Impact of control strategies on Thrips tabaci and its predator Aeolothrips intermedius on onion crops

Thrips tabaci (Thysanoptera: Thripidae) is a major pest of onion worldwide. In 2011, research was conducted in a commercial onion field in northwestern Italy to: (i) assess the presence of autochthonous onion thrips predators on the crop; and (ii) evaluate the impact of the commonly used insecticides and alternative pest management strategies on onion thrips and its autochthonous predators. Toxicity of the active ingredients on local populations of onion thrips and its predatory thrips was also evaluated in laboratory bioassays. During field surveys, the highest and lowest thrips infestations were observed in plots treated with lambda-cyhalothrin and spinosad, respectively. The effectiveness of spinosad on T. tabaci was also confirmed in laboratory bioassays. The dominant zoophagous species Aeolothrips intermedius (Thysanoptera: Aeolothripidae) was more adversely affected by treatment with lambda-cyhalothrin, confirmed by a decrease in predator/prey ratios. The use of spinosad and acibenzolar-S-methyl is suggested as an alternative to conventional insecticides for the preservation of A. intermedius, which proved to be a potential biological control agent of T. tabaci.

Effect of new and old pesticides onOrius armatus(Gross)—an Australian predator of western flower thrips,Frankliniella occidentalis(Pergande)

Orius armatus (Gross) is an important predator of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) in Australian glasshouse grown sweet pepper. The failure of O. armatus to establish in some glasshouses has been attributed to the use of newer, more non-selective pesticides, some of which are regarded to be compatible with integrated pest management. The residual toxicity (via direct and indirect contact) of several older and newer chemistry pesticides were evaluated. In addition, the effect of several systemic insecticides through insecticide-treated food-chain uptake was tested. Older chemistry pesticides (methamidophos, dimethoate) were toxic to Orius armatus, except pirimicarb which was non-toxic. Newer chemistry pesticides differed in their suitability. Abamectin was toxic to adults and nymphs. Chlorantraniliprole, imidacloprid and spirotetramat were non-toxic. Spinosad and spinetoram were moderately toxic to O. armatus. Spinosad also reduced fecundity by 20% compared to the untreated control. Pymetrozine was non-toxic, but females exposed to treated beans produced 30% fewer eggs and 20% fewer nymphs hatched compared to the untreated control. The selective pesticides do not necessarily facilitate the conservation of beneficials, and further assessment of the various developmental stages and other sub-lethal effects of chlorantraniliprole, imidacloprid, pymetrozine, spinetoram, and spirotetramat is recommended.

Evaluation of Imidacloprid and Cyantraniliprole for Suitability in Conservation Biological Control Program forOrius insidiosus(Hemiptera: Anthocoridae) in Field Pepper

Evaluation of Imidacloprid and Cyantraniliprole for Suitability in Conservation Biological Control Program for<i>Orius insidiosus</i>(Hemiptera: Anthocoridae) in Field Pepper

Biological control of western flower thrips,Frankliniella occidentalis(Pergande) (Thysanoptera: Thripidae), in gerberas, chrysanthemums and roses

Frankliniella occidentalis (Pergande), western flower thrips (WFT), is a major worldwide pest of vegetables and ornamental crops. The biology of WFT was examined on gerberas, chrysanthemums and roses in relation to plant stage (flowering and non-flowering), pupation site, soil moisture and plant parts often inhabited by adult and immature thrips. Four foliage thrips predators (Transeius montdorensis (Schicha), Orius armatus (Gross), Mallada signata (Schneider) and Neoseiulus cucumeris (Oudemans)) and three soil predators (Geolaelaps aculeifer (Canestrini), Steinernema feltiae (Filipjev) and Dalotia coriaria (Kraatz)) were studied to determine their ability to reduce the numbers of WFT on gerberas, chrysanthemums and roses. There was no difference in the number of adults that emerged from growing media of high or low moisture content on any host plant. There were also no differences in the total numbers of WFT recaptured from flowering gerberas, chrysanthemums or roses. However, about seven times the number of thrips were collected from flowering chrysanthemums compared with non-flowering chrysanthemums, indicating that the flowering plants were more suitable hosts. Of all thrips recollected, the greatest percentage was immature (larval and pupal) thrips (70%, 71% and 43%) on the flowers for gerberas, chrysanthemums and roses, respectively. The mean percentage of thrips that emerged as adults from the soil was very low (5.3 ± 1.2, 8.5 ± 2.9, 20.5 ± 9.1 and 28.2 ± 5.6%) on gerberas, flowering and non-flowering chrysanthemums, and roses, respectively. Simultaneous release of foliage and soil predators did not reduce the number of thrips beyond that caused by foliage predators alone. Of the foliage predators, T. montdorensis, O. armatus and N. cucumeris performed best, significantly reducing the numbers of adult and immature thrips on flowers and foliage by 30–99%. Further research is required to determine the most cost-effective rates of release in cut flower crops.

Suitable Food for the Mass Rearing of Wollastoniella rotunda (Heteroptera: Anthocoridae), a Predator of Thrips palmi (Thysanoptera: Thripidae)

Wollastoniella rotunda Yasunaga et Miyamoto is an effective predator of Thrips palmi Karny and a potential biological control agent for this pest of Japanese greenhouse vegetables. To determine alternative sources of prey for the mass rearing of W. rotunda used for T. palmi augmentative biocontrol, we examined the life history parameters of this predator as reared on two different prey species: Tyrophagus putrescentiae (Schrank) and Ephestia kuehniella Zeller eggs. When the predator nymphs were reared on T. putrescentiae and E. kuehniella at 25°C, their developmental times were 21.0 and 16.7 days, respectively, and their survival rates on T. putrescentiae and E. kuehniella at 25°C were 43% and 91%, respectively. The longevity of the predator females was 13.1 days on T. putrescentiae and 19.2 days on E. kuehniella, and their total fecundity was 15.0 eggs on T. putrescentiae and 56.5 eggs on E. kuehniella. The intrinsic rate of natural increase per day of W. rotunda on E. kuehniella (rm = 0.087) was greater than that on T. putrescentiae (rm = 0.031). We thus concluded that E. kuehniella is more suitable than T. putrescentiae as food for the mass rearing of W. rotunda.

Effects of floral and extrafloral resource diversity on the fitness of an omnivorous bug, Orius insidiosus

AbstractHabitat manipulation and increasing biodiversity are important approaches that enhance biological control of pests, but it is important to evaluate the relative benefits of specific plant species when designing conservation programs. Orius insidiosus Say (Hemiptera: Anthocoridae) is an important predator of thrips and aphids that also feeds on plants. It is the target of conservation biological control programs. Despite O. insidiosus' relevance, little is known about the effects of plant subsidies on predator performance or nutritional status. Here, we examined the influence of restricting the pollen and nectar resources of five plant species (alyssum, buckwheat, phacelia, fava bean, and chamomile), and how increasing plant diversity affects O. insidiosus fecundity, survival, and nutritional status. Plant species varied in their suitability for O. insidiosus, which was driven in part by the availability of the pollen or nectar resources. Offering plants as a mixture did not improve fecundity; however, the plant least preferred for oviposition under no‐choice tests (fava bean) became the preferred egg‐laying site when the plants were offered in combination. We conclude that the benefits obtained by O. insidiosus vary among plant species, and that increasing plant diversity can have unpredicted, positive effects on insect fitness.

Effect of Different Temperatures on Consumption of Two Spotted Mite,Tetranychus urticae, Eggs by the Predatory Thrips,Scolothrips longicornis

Environmental variables such as temperature are important factors affecting the efficacy of biological control agents. This study evaluated the predation rate of the predatory thrips Scolothrips longicornis Priesner (Thysanoptera: Thripidae) against the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) under laboratory conditions. Based on daily and total prey consumption of different life stages of S. longicornis on spider mite eggs at temperatures covering the range suitable for development and survival of the predator (15° C to 37° C, 60 ± 10% RH, 16:8 L:D), there was a significant effect of temperature on prey consumption. The number of prey consumed daily by first and second instar larvae increased linearly with increasing temperature from 15 °C to 37 °C, whereas daily consumption of preovipositing and postovipositing females was uninfluenced by temperature. Lower temperature thresholds for consumption by first and second instar larvae of S. longicornis was estimated to be 6.8 ± 0.04° C and 4.6 ± 0.03° C, respectively. The daily consumption of ovipositing females followed a nonlinear pattern, with maximum daily predation estimated at 32.8° C. From the model used to describe consumption of ovipositing females, an upper threshold for consumption of 41.4° C was estimated. The performance of S. longicornis at the different temperatures is discussed in relation to its practical use in integrated pest control programs.

Potential use of the fungus Beauveria bassiana against the western flower thrips Frankliniella occidentalis without reducing the effectiveness of its natural predator Orius sauteri (Hemiptera: Anthocoridae)

Orius sauteri (Poppius; Hemiptera: Anthocoridae) is an important predator of western flower thrips, Frankliniella occidentalis (Pergande; Thysanoptera: Thripidae). O. sauteri would be directly exposed to the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin in the field should the fungus be used as a biopesticide. If the fungus were to negatively affect O. sauteri in agro-ecosystems, predation of F. occidentalis by O. sauteri may be limited. The present study was undertaken to evaluate the insecticidal activity of strain B.bassiana-RSB of B. bassiana, which is highly virulent to F. occidentalis, on the predator under laboratory conditions. Results showed that, regardless of the concentration applied to first instars, Bb-RSB was not insecticidal against O. sauteri, nor did direct applications affect the developmental rate of the predator. Significant differences in developmental rates and adult longevity were observed between O. sauteri that fed on Bb-RSB-infected F. occidentalis cadavers and those that fed on untreated thrips. Developmental time (from first instar to adult) increased from 0.3 to 0.7 days and adult longevity decreased by 0.8 to 1.2 days for predators fed thrips treated with low and high concentrations of strain Bb-RSB, respectively, compared with predators fed on untreated thrips. However, these differences were only 3–13% of mean values for the controls, suggesting that the effects of Bb-RSB on O. sauteri are relatively minor. These findings highlight the potential use of O. sauteri in combination with B. bassiana for the biocontrol of F. occidentalis, but field tests must be performed to confirm their compatible use.

The response of a southern strain of Orius majusculus (Reuter) (Hemiptera: Anthocoridae) to photoperiod and light intensity: Biological effects and diapause induction

Short-day induced reproductive diapause makes supplementary lighting indispensable to the use of thrips predator Orius majusculus (Reuter) for biological control in greenhouses during the winter. In order to reduce energy costs, strains with a shorter critical day-length and the ability to avert diapause under low-intensity supplementary lighting, are desirable. With this in mind, a southern strain of O. majusculus from a locality (37.0°N, 30.5°E) in Antalya, Turkey was investigated. Its response to the photoperiod was studied at day-lengths of 11.5, 12, 12.5, 13.5, 14.5 and 16h, at 26±1°C, 60±10% r.h. and 2400 lux. The duration of nymphal development and developmental time were longer in both sexes at the short day-length, 11.5h, than at other day-lengths. Significant but inconsistent effects of the photoperiod were found on the incubation period, generation time, egg hatch rate and nymph survival. The pre-oviposition period and longevity tended to be longer at the short day-length. Fecundity was also affected, being lower at 12h, than at 14.5 and 16h. The sex ratio was not influenced by the photoperiod. The critical day-length was between 11.5 and 12h, and all females entered reproductive diapause at 11.5h, while only 25% did so at 12h, and none at 14.5 and 16h. The effect of light intensity was determined at 10, 25, 50, 100, 200 and 2400 lux, at 26±1°C, 60±10% r.h. and a day-length of 12.5h. The duration of nymphal development, developmental time and generation time were longer in both females and males at 200 lux than at other light intensities. The incubation period, egg hatch rate, pre-oviposition period, longevity, fecundity and sex ratio were not affected by the light intensities that were tested. An inconsistent influence was found on nymph survival. The oviposition period was longer at 2400 lux than at lower light intensities. The light intensities did not affect diapause incidence. In conclusion, O. majusculus from Antalya have a shorter critical day-length than the northern strains and therefore would require shorter supplementary lighting if used as a biological control in greenhouses. Diapause would be averted under a supplementary light of 10 lux and over with little or no effects on biological characteristics.

Diversidade de predadores em coentro, endro e funcho sob manejo orgânico

Espécies vegetais da família Apiaceae podem proporcionar recursos vitais para insetos predadores de pragas agrícolas, promovendo sua eficiência como agentes de controle biológico devido à oferta de recursos como sítios de refúgio, proteção e alimentação. Assim, o objetivo deste trabalho foi avaliar a atração de insetos predadores pelas apiáceas coentro (Coriandrum sativum L.), endro (Anethum graveolens L.) e funcho (Foeniculum vulgare Mill.). O experimento foi conduzido no campus da Universidade Federal de Lavras (UFLA), Lavras, MG, em blocos completos ao acaso, com três tratamentos e quatro repetições. Coletas semanais foram realizadas por meio de batida das plantas em bandejas, sendo os predadores aspirados e acondicionados em frascos com álcool 70%. Determinaram-se a curva do coletor, a riqueza de espécies, o índice de diversidade de Shannon-Wienner e o índice de similaridade (análise de Cluster). O funcho apresentou maior índice de Shannon-Wienner (H' = 1,104) e riqueza, enquanto o coentro mostrou maior abundância, sobretudo para a espécie Orius insidiosus (Hemiptera: Anthocoridae), um importante predador de tripes em hortaliças. Outras espécies predadoras de pragas de hortaliças foram encontradas, de maneira geral, em todas as apiáceas, destacando-se os adultos e larvas de coccinelídeos, importantes predadores de pulgões. A análise de Cluster indicou maior similaridade entre funcho e endro (55,03%). O período de floração promoveu considerável aumento na abundância de predadores, sobretudo no coentro.

Biological control of aphids in the presence of thrips and their enemies

Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.

Life tables for the guava psyllid Triozoida limbata in southeastern Brazil

The aim of this study was to identify, quantify, and determine the importance of biological control agents of the psyllid Triozoida limbata (Enderlein) (Hemiptera: Sternorrhyncha: Triozidae). Ecological life tables were developed during four periods to determine the critical stage and key mortality factors of this pest. Predation and parasitism were found to be the two major factors driving the population dynamics of this pest. The major predators of eggs and nymphs of first and second instars were coccinellids, predatory thrips, lacewings, ants, and spiders, while the major predators of third, fourth, and fifth instars were several species of predatory wasps and syrphids. The endoparasitoid Psyllaephagus sp. (Hymenoptera: Encyrtidae) parasitized fifth instar psyllids. The fifth instar was found to be the critical mortality stage of T. limbata, and key mortality factors include the parasitoid Psyllaephagus sp. and predatory wasps.

The role of omnivory in the conservation of predators: Orius majusculus (Heteroptera: Anthocoridae) on sweet alyssum

In conservation biological control programs, provision of the required resources (shelter, food, oviposition sites) can be achieved by means of the use of insectary plants. This is especially important in the case of omnivorous predators that feed on prey and plant materials, and where the availability of plant resources plays a significant role in their conservation. An important predator of thrips and other pests in the Mediterranean is the omnivorous bug Orius majusculus (Reuter) (Hemiptera: Anthocoridae). The objective of this study was to evaluate the fertility, fecundity and longevity of O. majusculus on alyssum, (Lobularia maritima L.) with and without prey (Ephestia kuehniella eggs), and compare it with green bean pods. Additionally, the effects of the breeding colony of the individuals on the fertility of O. majusculus were studied. Fecundity on both plants without prey was low; however the addition of prey significantly increased the number of eggs laid, especially on alyssum. The longevity differed significantly among diets, being longer for alyssum with prey eggs. Survival on alyssum without prey was not statistically different from green bean with prey, which shows the potential of alyssum to conserve O. majusculus during times of prey scarcity. The fertility of O. majusculus females was significantly higher on the diets of both plant materials when prey was included. Our results showed that alyssum can provide resource subsidies for O. majusculus during times of prey scarcity in the field.

Effect of a heterospecific predator on the oviposition behavior of Phytoseiulus persimilis

Oviposition rate is affected by several factors such as con- and heterospecific competitors, food availability and patch quality. When the species have interacted for a sufficient period of time, the predator could profit from the ability to associate odors from the competitor with the risk of its eggs being attacked or eaten by that competitor. We examined the oviposition rate of Phytoseiulus persimilis for a response for signals emanating from its heterospecific competitor, Frankliniella occidentalis in the presence of their shared prey, Tetranychus urticae on rose and bean leaf patches . In the treatments in which the predatory mite and thrips were exposed to each other, a significant reduction was observed in the number of deposited eggs compared to the control experiment. The same result was found in an experiment in which the exposure time was limited to the pre-oviposition period of the predatory mite. Increasing the time elapsed since the two competitors were exposed to each other to 2 days, the effect of thrips on the oviposition rate of the predatory mite had vanished and approached the oviposition rate in the control experiment. The plant species used as a substrate for the interspecific interactions did not significantly alter the results. We discuss the potential consequences of the presence of thrips for the ability of P. persimilis to control the two spotted spider mite.

福岡県における促成栽培イチゴの育苗期に発生するハダニ類の土着天敵

To validate the possibility of integrated pest management (IPM) utilizing natural enemies against spider mites (Acari: Tetranychidae) during the seedling-rearing period of strawberry, we investigated the dominant species of their natural enemies both on kidney bean traps infested with Tetranychus urticae Koch and on strawberry seedlings in four seedling-rearing fields per year in 2010 and 2011. While the predatory thrips, Scolothrips takahashii Priesner and phytoseiid mites were predominantly captured on the traps, predatory thrips was the only natural enemy observed on strawberry seedlings in all fields. Even when the densities of spider mites on strawberry seedlings were relatively low, predatory thrips were frequently observed. These results suggest that S. takahashii could be an effective agent to control spider mites in IPM for a seedling-rearing period of strawberry.

Management of chilli thrips Scirtothrips dorsalis (Thysanoptera: Thripidae) on peppers by Amblyseius swirskii (Acari: Phytoseiidae) and Orius insidiosus (Hemiptera: Anthocoridae)

Chilli thrips, Scirtothrips dorsalis Hood, recently established in southeast of the United States, poses an economic threat to a wide-range of ornamental and vegetable plants. In this study, we examined biological control of chilli thrips with a predatory mite, Amblyseius swirskii Athias-Henriot, and the insidious flower bug, Orius insidiosus Say. Laboratory tests showed that at equivalent rates, O. insidiosus was a more effective predator of adult thrips compared with A. swirskii, although the same trend was not observed with thrips larvae. At a rate of 20 predators per infested pepper plant, both predator species maintained ⩽0.5 thrips per leaf and <1% foliar damage after 5 weeks on all pepper varieties, compared with up to 13 thrips and >40% damage on control plants. Slightly less effective control was observed in a second study, where a reduced rate of predators (10 per plant) resulted in approximately 20% foliar damage, while damage was > 90% on control plants. Plants treated with O. insidiosus alone or in combination with A. swirskii had consistently fewer adult thrips and plant damage compared with A. swirskii alone. Furthermore, we observed different susceptibilities to thrips among pepper varieties, with damage lowest on ‘Trinidad perfume’ and ‘Brigadier hybrid’ compared with ‘Large red cherry’, and ‘Serrano’. Our results show that both predators were effective predators of chilli thrips on pepper and suggest that both species could be used in combination without decreased efficacy through intraguild predation.

How many Orius laevigatus are needed for effective western flower thrips, Frankliniella occidentalis, management in sweet pepper?

Frankliniella occidentalis (Pergande) is a primary pest of greenhouse crops worldwide, in organic and integrated pest management control practices, Orius spp. are frequently released for thrips control. However, Orius spp. are relatively expensive to produce. More cost-efficient rearing systems and reduced release rate might reduce the expense. In these trials, we released Orius laevigatus (Fieber) at different rates with or without simultaneous release the predatory mite Amblyseius swirskii Athias-Henriot, another known thrips predator, which is less expensive to rear. There was no significant difference in the number of O. laevigatus recovered in which either 2 or 6 individuals were released per square meter, and there was no difference in thrips control among any of the release strategies using O. laevigatus, suggesting that a reduced release rate can maintain effective thrips control. There was no significant difference in the quality or quantity of the pepper yield between treatments in which either 2 or 6 Orius/m 2 or Orius plus A. swirskii were released.

Effect of Temperature on Life Table Parameters of Predatory Thrips Scolothrips longicornis (Thysanoptera: Thripidae) Fed on Twospotted Spider Mites (Acari: Tetranychidae)

Environmental variables such as temperature are important factors that affect the efficiency of biological control agents. This study examined the effect of temperature on the sex ratio, longevity, oviposition periods, fecundity and life table parameters of the predatory thrips Scolothrips longicornis Priesner (Thysanoptera: Thripidae) fed on twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), at six constant temperatures: 15, 20, 26, 30, 35, and 37 degrees C. Approximately 75% of the progeny were female, except at 37 degrees C, at which temperature the proportion of males increased. Adult longevity as well as the preoviposition, oviposition, and postoviposition periods decreased significantly with temperature. Thus, adults lived for approximately 5 wk at 15 degrees C and < 1 wk at 37 degrees C with preoviposition, oviposition, and postoviposition periods ranging from 6.4 to 0.4, 24.4-3.1, and 7-0.8 d between the two temperature extremes, respectively. The maximum (56.48 eggs) and minimum (11.69 eggs) value of total fecundity was recorded at 26 and 37 degrees C, respectively. The intrinsic rate of natural increase (r(m)) of S. longicornis increased linearly with increasing temperature from 0.056 d(-1) at 15 degrees C to 0.310 d(-1) at 35 degrees C. The lower temperature threshold for the population increase of S. longicornis was estimated to be around 5 degrees C. The data suggest that the upper temperature threshold for the predatory thrips is approximately 37 degrees C. The results showed that populations of S. longicornis are able to develop at a broad range of temperatures and that this predator is well adapted to the high temperatures that occur in the Mediterranean region.