Thrips Larvae Research Articles

Altered Gene Expression: Induction/Suppression in Leek Elicited by Iris Yellow Spot Virus Infection (IYSV) Egyptian Isolate

ABSTRACTLeek (Allium porrum) has become one of the major leafy vegetable crops in Egypt and all over the world. Iris yellow spot virus (IYSV) was observed on leek plants in eight different governorates in Egypt, in fields near to onion fields. The symptoms in infected leek plants included yellowish or tan diamond-shaped or irregularly shaped lesions on leaves and flower stalks. Necrotic areas developed on leaves, and some plants had elongated brown lesions or brown flecks resembling thrips injury. Moreover, thrips larvae and adults feed with a punch-and-suck behavior that removes leaf chlorophyll, causing white to silver patches and streaks, which were observed on all infected plants. The plant samples were collected and subjected to ELISA test using IYSV polyantiserum. The results revealed that about 90% of the collected samples with symptoms were positive. For further confirmation, the ELISA positive samples were subjected to PCR amplification using nuclear coat protein specific primers. The PCR results were in agreement with the results obtained by ELISA. Thrip tabaci adults were reared on the infected plant and biological transfer was performed onto new healthy plants. After 15 days to 4 weeks post inoculation, symptoms were observed on the plant. Biologically infected plant samples were collected at different times after thrips-inoculation and the extracted RNA was subjected to Real Time PCR using the coat protein gene primers. The results showed that the expression of the coat protein fluctuated but reached its peak on day five (264%). Differential display technique was performed on the newly infected plant tissues to identify changes in gene expression in leek elicited by IYSV that causes a symptomatic phenotype. Both up- and down- regulated genes were observed in infected plants conjugated with the healthy ones. Sequence analysis of the up-regulated genes was performed and the encoding sequence analysis showed that the obtained genes include: MFS family protein, Pathogenesis- related protein, Mitogen-activated protein kinase, N-acetylserotonin O-methyltransferase-like protein, Serine/threonine-protein kinase, and Putative Retrosat2 Ty3-Gypsy retroelement. On the other hand, only one down-regulated gene was identified, alpha- tubulin suppressor-like protein. Most of the identified genes are suppress defensin genes (innate/adaptive). It can be concluded that viral infection is capable of inducing a huge number of genes which are important in the plant immune system.

Juvenile prey induce antipredator behaviour in adult predators

It is generally assumed that the choice of oviposition sites in arthropods is affected by the presence of food for the offspring on the one hand and by predation risk on the other hand. But where should females oviposit when the food itself poses a predation risk for their offspring? Here, we address this question by studying the oviposition behaviour of the predatory mite Amblyseius swirskii in reaction to the presence of its counterattacking prey, the western flower thrips Frankliniella occidentalis. We offered the mites a choice between two potential oviposition sites, one with and one without food. We used two types of food: thrips larvae, which are predators of eggs of predatory mite but are consumed by older predator stages, and pollen, a food source that poses no risk to the predators. With pollen as food, the predators preferred ovipositing on the site with food. This might facilitate the foraging for food by the immature offspring that will emerge from the eggs. With thrips as food, female predators preferred ovipositing on the site without thrips. Predators that oviposited more on the site with thrips larvae killed more thrips larvae than females that oviposited on the site without food, but this did not result in higher oviposition. This suggests that the females killed thrips to protect their offspring. Our results show that predators display complex anti-predator behaviour in response to the presence of counter-attacking prey.

Evaluation of Insecticides Against the Western Flower Thrips,Frankliniella occidentals(Thysanoptera: Thripidae), in the Laboratory

To evaluate insecticide efficacy against the western flower thrips, Frankliniella occidentalis (Pergande), the first step was to select a host suitable for rearing sufficient numbers of this pest. The influence on the development and survival rates of this thrips of each of 3 selected leguminous hosts, Canavalia gladiata (Jacq.) DC, Lablab purpureus (L.) Sweet and Phaseolus vulgaris L., was examined and compared to the other in the laboratory. Results showed that the number of newly hatched larvae (543.20), the survival rates of 2nd to 4th instar (89.12%), and the eclosion (73.17%) on C. gladiata were significantly higher than on L. purpureus and P. vulgaris, and also the developmental time from egg to adult was the shortest on C. gladiata (10.15 d). Therefore, C. gladiata was selected as the best host among these legumes for rearing the thrips in the laboratory. Thirty-six insecticides commonly used in China to protect flowers and vegetables were chosen from 8 chemical classes for assay using a glass-vial method to evaluate their toxicities against thrips larvae in a laboratory. Based on LC50 values, and on the need to rotate and alternate the application of insecticides, 12 highly efficacious insecticides from different IRAC mode of action groups were evaluated against adult females. Although the ranking of toxicities to adults was slightly different from that to larvae, the results showed that the insecticides with high efficacy against larvae were also effective against adults. These findings will facilitate the selection of insecticides for effective control of western flower thrips and for developing insecticide resistance man agement strategies.

Effect of Jasmonic Application on Economically Insect Pests and Yeald in Spring Wheat

Field trials were conducted in spring wheat to observe effects of jasmonic acid (JA) on aphids, thrips and wheat blossom midge (WBM). Two spring wheat varieties (Triso and Kadrilj) were sprayed twice, with two concentrations of JA plus control. Wheat pests and associated natural enemies (Coccinellidae, Empididae and Aphelinidae) were surveyed by direct count and sweep net methods. Thrips larvae and adults and WBM larvae were estimated by dissecting wheat ears. Wheat midge larvae were monitored using white traps in treated and untreated plots. At the end of season, wheat yield was assessed in treated and control plots. There was a significant difference in the number of insect pests and their natural enemies between treatments in both varieties. Plants in control plots had higher numbers of aphids, thrips and midges than in treated plots. There were more aphids, thrips and midges on the variety ‘Triso’ than on ‘Kadrilj’. JA application enhanced wheat yield in treated plots compared to control plots. The results indicated that JA mediated induction of plant defense in wheat plants can improve resistance against insect herbivores. JA could be used to develop environmentally sound crop management with reduced insecticide applications.

Species Diversity, Seasonal Dynamics, and Vertical Distribution of Litter—Dwelling Thrips in an Urban Forest Remnant of South China

Litter—dwelling thrips are an important component of soil macroinvertebrates in tropical and subtropical regions. However, little is known about assemblage composition, seasonal abundance and vertical distribution of litter—dwelling thrips. A survey of forest litter—dwelling thrips and other soil macroinvertebrates was conducted in an urban forest remnant at Guangzhou, China during 2004–2005 and 2008–2009. A total of 835 Tullgren samples were collected during the study. Thysanoptera constituted 6.5% of total litter—dwelling macroinvertebrate individuals extracted, representing three families, 19 genera, and 25 species. Psalidothrips ascitus Ananthakrishnan (Thysanoptera: Phlaeothripidae) and Hyidiothrips guangdongensis Wang, Tong and Zhang represented 78.5% of all individuals of litter—dwelling thrips during the survey. Numbers of species and density of leaf—litter thrips fluctuated between different months. Density of litter thrips increased from March until October, reaching a maximum of 41.1 individuals/m2 followed by a decrease. In January and February only a few larval thrips were present. Species diversity gradually increased from July (four species) to December (10 species), and then declined rapidly. The vertical distribution showed that the leaf—litter thrips species richness and abundance decreased significantly with soil depth; they were found only in the litter layer and upper soil layer (0-5 cm in depth) and were entirely absent in deeper soil layers. The results suggest that litter—dwelling thrips are a common group of litter invertebrates with high species diversity in subtropical regions. These urban forest remnants should be given special consideration in forest conservation planning, because of their significance as refugia for the litter invertebrate assemblages, especially for leaf—litter thrips.

Symbiotic bacteria (Erwinia sp.) in the gut of Frankliniella occidentalis (Thysanoptera: Thripidae) do not affect its ability to transmit tospovirus

Tomato spotted wilt virus (TSWV) is one of the most harmful plant viruses and one of its most important vectors is the western flower thrips [Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)]. Recently, we reported the close association of Erwinia sp. gut bacteria with this species of thrips. The first instar larvae acquire these bacteria from their food source. A high proportion of adult western flower thrips transmit TSWV after acquiring the virus during the first larval stage when there are no bacteria in their gut. A considerably lower proportion of adults that acquire the virus early in the second instar transmit virus and none of those exposed to virus late on in the second instar do so. The highest prevalence and total number of symbiotic bacteria are recorded in the guts of second instar thrips. This leads to the hypothesis that the build up of bacteria in the gut reduces the acquisition of TSWV, resulting in a lower capacity to transmit the virus. To test this hypothesis, the transmission of this virus by symbiotic and aposymbiotic adult thrips of the NL3 population was studied. Comparison of virus transmission by adult thrips, the larvae of which either had or lacked gut bacteria and were exposed to virus in either the first or second instar, revealed no difference in the ability of symbiotic and aposymbiotic adults to transmit this virus. We conclude that virus transmission is not affected by the number of the symbiotic bacteria Erwinia sp. present in the gut of thrips larvae.

Abundance of Thrips obscuratus (Crawford) (Thysanoptera: Thripidae) during wine grape flowering in different regions in New Zealand

As a first step in understanding the pest status of thrips in wine grapes in New Zealand, we aimed to determine the species composition of thrips in grape inflorescences in four grape-growing regions of the country (sampling grape cv. ‘Chardonnay’ from 18 growers) and to quantify their abundance. Of the regions, by far the largest numbers of thrips were recorded from Canterbury (mean number of thrips per inflorescence from the raw data=48.6, 9.3, 9.4 and 6.4 for Canterbury, Auckland, Hawke's Bay and Marlborough, respectively). Of a subsample of 15% (536 thrips) identified, all but one were New Zealand flower thrips females (NZFT, Thrips obscuratus). The largest numbers of thrips were measured on the windward sides of three out of four vineyards sampled. The presence of thrips eggs and larvae suggests that grape vines are breeding hosts for NZFT, but further research is now needed on the thrips’ life cycle and its distribution and numbers in New Zealand vineyards in order to determine the risk this potential pest presents to the wine industry.

Influences of Botanical Pesticides and Biological Agents on Orius Laevigatus - Frankliniella Occidentalis Dynamics Under Greenhouse Conditions

Influences of Botanical Pesticides and Biological Agents onOrius Laevigatus - Frankliniella OccidentalisDynamics Under Greenhouse ConditionsWe assessed the influence of nine biopesticides on adults and larvae of western flower thrips (WFT),Frankliniella occidentalis(Pergande) and its predator, the anthocoridOrius laevigatus(Fieber) under Mediterranean greenhouse conditions. Trials were carried out in a strawberry crop where both species had naturally established. Foliar sprays were applied weekly for one month. Treatments did not provide sufficient control of larval and adultF. occidentalis. The negative effects on the dynamics of the predator were evident only with the use of some specific products. The botanical insecticides rotenone and neem, and the nematodeSteinernema feltiae(Filipjev) reducedO. laevigatusnumbers, and these effect are evident in the adult stage ofO. laevigatus. Such products have determined a reduction of the population of the predator from the first treatments even if the incidence was not very high. We conclude that the use of some botanical pesticides and nematodes against WFT is uneconomical and possibly disadvantageous where there is an established predator-prey population.

Intraguild predation among plant pests: western flower thrips larvae feed on whitefly crawlers

Omnivores obtain resources from more than one trophic level, and choose their food based on quantity and quality of these resources. For example, omnivores may switch to feeding on plants when prey are scarce. Larvae of the western flower thrips Frankiniella occidentalis Pergande (Thysanoptera: Thripidae) are an example of omnivores that become predatory when the quality of their host plant is low. Western flower thrips larvae usually feed on leaf tissue and on plant pollen, but may also attack eggs of predatory mites, their natural enemies, and eggs of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae), one of their competitors. Here, we present evidence that western flower thrips larvae prey on Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), another competitor for plant tissue. We tested this on two host plant species, cucumber (Cucumis sativa L.), considered a host plant of high quality for western flower thrips, and sweet pepper (Capsicum annuum L.), a relatively poor quality host. We found that western flower thrips killed and fed especially on whitefly crawlers and that the incidence of feeding did not depend on host-plant species. The developmental rate and oviposition rate of western flower thrips was higher on a diet of cucumber leaves with whitefly crawlers than on cucumber leaves without whitefly crawlers, suggesting that thrips do not just kill whiteflies to reduce competition, but utilize whitefly crawlers as food.

Aggregation pattern, sampling plan, and intervention threshold for Pezothrips kellyanus in citrus groves

Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) has recently emerged as an international pest of citrus. It causes severe scarring of the fruit surface and commercial downgrading of fresh fruit production. The goals of this article were to determine the aggregation patterns of P. kellyanus on citrus, to establish an efficient sampling plan to assess their population density, and to develop an environmental economic injury level (EEIL). The study was conducted in 14 citrus groves in Valencia (Spain) during 2008 and in eight citrus groves during 2009. On each grove, population densities of thrips were monitored weekly on citrus flowers and fruitlets during the flowering and fruit setting period. Final damage was determined on developed fruits. Pezothrips kellyanus was the most abundant thrips species, with 73.5% of adults and 92.1% of larvae present, followed by Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), with 18.2 and 3.5%, respectively. First description of first instars of P. kellyanus is provided. Our results prove that thrips show clumped population distributions, with no differences in aggregation parameters between flowers and fruitlets, thrips species, larval stages, or sex of adults. Immature thrips showed a higher aggregation (Taylor’s value of b = 1.40 ± 0.06) than adults (b = 1.19 ± 0.04). Fruit damage by P. kellyanus on developed fruits was strongly correlated with percentage of fruitlets with immature P. kellyanus (r = 0.897; n = 22). Based on the percentage of fruitlets occupied by immature thrips, the economic injury levels and EEIL were calculated (using chlorpyrifos as insecticide) obtaining values of 7 and 12%, respectively. Insecticide treatments will be necessary if more than 12% of fruitlets are infested by thrips larvae. Constant precision (D = 0.25) sampling plans developed show that 200 sample units should be observed in enumerative sampling, and 310 in binomial presence–absence sampling, at population levels of immatures on fruitlets around the EEIL.

Botanical Insecticides in Controlling Kelly's Citrus Thrips (Thysanoptera: Thripidae) on Organic Grapefruits

Kelly's citrus thrips, Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) was first recorded in Cyprus in 1996 and became an economic citrus pest. In Cyprus, Kelly's citrus thrips larvae cause feeding damage mainly on immature lemon and grapefruit fruits. Use of botanical insecticides is considered an alternative tool compared with synthetic chemicals, in offering solutions for healthy and sustainable citrus production. During 2008-2010, the efficacy of the botanical insecticides azadirachtin (Neemex 0.3%W/W and Oikos 10 EC), garlic extract (Alsa), and pyrethrins (Vioryl 5%SC) was evaluated in field trials against Kelly's citrus thrips larval stage I and II aiming at controlling the pest's population and damage to organic grapefruit fruits. In each of the trial years treatments with pyrethrins and azadirachtin (Neemex 0.3%W/W) were the most effective against Kelly's citrus thrips compared with the untreated control (for 2008: P < 0.018; for 2009: P < 0.000; for 2010: P < 0.008). In 2008, the mean number of damaged fruits in treatments with pyrethrins and Neemex was 9.6 (19.2%) and 9.7 (19.5%) respectively, compared with 12.2 (24.3%) in the untreated control. In 2009, the mean number of damaged fruits in treatment with pyrethrins was 3.7 (7.3%) and 3.9 (7.8%) in treatment with Neemex compared with 8.6 (17.3%) in the untreated control, while in 2010 the mean damaged fruits in these treatments was recorded at 18.7 (37.5%) and 19.6 (39.2), respectively, compared with 29.6 fruits (59.2%) in the control. Oikos 10 EC showed significant effect only in 2009 and 2010. In these years, the mean number of damaged fruits was recorded at 5.5 and 21.2 compared with 8.6 and 29.6 fruits in the untreated control, respectively. Garlic extract showed the lowest effect from all the botanicals used compared with the untreated control.

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.

Variation within and betweenFrankliniellaThrips Species in Host Plant Utilization

Anthophilous flower thrips in the genus Frankliniella (Thysanoptera: Thripidae) exploit ephemeral plant resources and therefore must be capable of successfully locating appropriate hosts on a repeated basis, yet little is known of interspecific and intraspecific variation in responses to host plant type and nutritional quality. Field trials were conducted over two seasons to determine if the abundance of males and females of three common Frankliniella species, F. occidentalis (Pergande), F. tritici (Fitch) and F. bispinosa (Morgan), their larvae, and a key predator, Orius insidiosus (Say) (Hemiptera: Anthocoridae) were affected by host plant type and plant nutritional quality. Two host plants, pepper, Capsicum annuum L. (Solanales: Solanaceae) and tomato, Solanum lycopersicum L. that vary in suitability for these species were examined, and their nutritional quality was manipulated by applying three levels of nitrogen fertilization (101 kg/ha, 202 kg/ha, 404 kg/ha). F. occidentalis females were more abundant in pepper than in tomato, but males did not show a differential response. Both sexes of F. tritici and F. bispinosa were more abundant in tomato than in pepper. Larval thrips were more abundant in pepper than in tomato. Likewise, O. insidiosus females and nymphs were more abundant in pepper than in tomato. Only F. occidentalis females showed a distinct response to nitrogen fertilization, with abundance increasing with fertilization. These results show that host plant utilization patterns vary among Frankliniella spp. and should not be generalized from results of the intensively studied F. occidentalis. Given the different pest status of these species and their differential abundance in pepper and tomato, it is critical that scouting programs include species identifications for proper management.

Compatibility of spinosad with predaceous mites (Acari) used to control Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Spinosad is a biopesticide widely used for control of Frankliniella occidentalis (Pergande). It is reported to be non-toxic to several predatory mite species used for the biological control of thrips. Predatory mites Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese) have been used for control of F. occidentalis. This study investigated the impact of direct and residual toxicity of spinosad on F. occidentalis and predatory mites. The repellency of spinosad residues to these predatory mites was also investigated. Direct contact to spinosad effectively reduced the number of F. occidentalis adults and larvae, causing > 96% mortality. Spinosad residues aged 2-96 h were also toxic to F. occidentalis. Direct exposure to spinosad resulted in > 90% mortality of all three mite species. Thresholds for the residual toxicity (contact) of spinosad (LT25 ) were estimated as 4.2, 3.2 and 5.8 days for T. montdorensis, N. cucumeris and H. miles respectively. When mites were simultaneously exposed to spinosad residues and fed spinosad-intoxicated thrips larvae, toxicity increased. Residual thresholds were re-estimated as 5.4, 3.9 and 6.1 days for T. montdorensis, N. cucumeris and H. miles respectively. Residues aged 2-48 h repelled T. montdorensis and H. miles, and residues aged 2-24 h repelled N. cucumeris. Predatory mites can be safely released 6 days after spinosad is applied for the management of F. occidentalis.

Seasonal abundance and spatial distribution of larval and adult thrips (Thysanoptera) on weed host plants in mango orchards in Penang, Malaysia

The spatial distribution of larval and adult thrips (Thysanoptera) was studied on mango panicles, Mangifera indica L., on Penang Island, Malaysia, during two consecutive mango flowering seasons from December 2008 to March 2009 and from August to September 2009. Larval and adult thrips were sampled from mango panicles using the carbon dioxide (CO2) collection technique weekly in treated and untreated orchards. Seasonal abundance and dispersion pattern of thrips were investigated on weed host plants in the treated orchard between June 2008 and March 2009. Spatiotemporal dynamics of larvae and adults was analyzed using Taylor’s Power Law (TPL), Lloyd’s Index (LI), and Green’s Index (GI). Thrips hawaiiensis (Morgan) was the dominant thrips species recovered from mango panicles and weeds in the treated orchard, whereas Scirtothrips dorsalis (Hood) was the most abundant species captured in the untreated orchard. Thrips adults and larvae analyzed via dispersion indices were found to be aggregated in mango panicles in both orchards. The value of the aggregation index (b) of TPL for the total number of adult thrips was significantly higher in the treated orchard than in the untreated orchard, whereas slopes of TPL for the total number of larval thrips did not differ significantly between treated and untreated orchards. All adult thrips species were distributed regularly on the weed plants; however, their larvae were aggregated. It is concluded that pesticide treatment caused adult thrips to become more aggregated on mango panicles, hiding in flower parts that were less exposed to the chemicals.

Toxic and behavioural effects of carvacrol and thymol on Frankliniella occidentalis larvae

Bioassays using bean leaf discs were conducted to investigate toxic and behaviour-modifying effects of carvacrol and thymol, two monoterpenoid phenols, on second instar larvae of Frankliniella occidentalis (Thysanoptera: Thripidae) at concentrations of 0.1% and 1%. We tested the contact toxicity of carvacrol and thymol to F. occidentalis larvae and studied the settlement preference of thrips larvae for treated or untreated bean leaf discs and the effects of the compounds on their feeding activity. Mortality rates after 24 h were 24.1% for carvacrol at 1% concentration, 16.5% for carvacrol at 0.1%, 7.7% for thymol at 1% concentration and 3.6% for thymol at 0.1%. Thrips larvae showed a significant preference for untreated leaf discs in choice tests with carvacrol 1% or thymol 1%. Likewise, in the no-choice tests feeding damage after 24 h was significantly lower on leaf discs treated with 1% carvacrol or 1% thymol compared to the control, but not on discs treated with 0.1% concentration of either compound. We conclude that an application of carvacrol or thymol to bean leaves does not result in a high mortality of F. occidentalis larvae but affects their behaviour.

ミカンキイロアザミウマFrankliniella occidentalis (Pergande)に対する高濃度炭酸ガスの殺虫効果

The effectiveness of carbon dioxide for use as an insecticide was examined by exposing adults and larvae of the western flower thrips (Frankliniella occidentalis) to high concentrations of the gas. Treatment of adults with 20 to 30%CO2 for 24h at 24°C resulted in a proportional increase in mortality, reaching 100% at 30%CO2 or higher concentrations. The time required for 100% mortality at 60%CO2 was less than 24h at 24°C, less than 10h at 30°C, and less than 4h at 34°C. The findings indicated that mortality increased in proportion to carbon dioxide concentrations and treatment temperatures, and that this tendency was common to adult and larval stages. It therefore seems advisable for treatment with high concentration CO2 to be applied to nursery systems for “thrips-free seedlings.”

Effects of Metarhizium anisopliae on searching, feeding and predation by Orius albidipennis (Hem., Anthocoridae) on Thrips tabaci (Thy., Thripidae) larvae

The generalist predator Orius albidipennis Reut. (Hem., Anthocoridae) and entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (Ascomycota: Clavicipitaceae) are important biocontrol agents of Thrips tabaci Lindeman (Thys., Thripidae) in most greenhouses. In this study, we estimated searching time, feeding time and predation rate in O. albidipennis feeding on untreated and treated thrips larvae which had been inoculated with three concentrations of M. anisopliae V275 at four time intervals; 0, 24, 48 and 72 h after infestation. Applied concentrations were 1×103, 2×104 and 2×105 conidia/mL which roughly correspond to the LC25, LC50 and LC75 for second instar-larvae. O. albidipennis responded to the presence of the M. anisopliae on the treated hosts by increasing the searching time and decreasing feeding time and predation rate levels. It was also able to detect and avoid treated patches.

Prey Preference of the Predatory Mite,Amblyseius swirskiibetween First Instar Western Flower ThripsFrankliniella occidentalisand Nymphs of the Twospotted Spider MiteTetranychus urticae

The prey preference of polyphagous predators plays an important role in suppressing different species of pest insects. In this study the prey preference of the predatory mite, Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) was examined between nymphs of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and first instar larvae of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), as well as between active and chrysalis spider mite protonymphs and active and chrysalis spider mite deutonymphs. The study was done in the laboratory on bean leaf discs at 25 ± 1° C and 70 ± 5% RH. Amblyseius swirskii had a clear preference for thrips compared to both spider mite protonymphs and deutonymphs. About twice as many thrips as spider mites were consumed. Amblyseius swirskii did not show a preference between active and chrysalis stages of spider mites.

Insectoacaricidal and deterrent activities of extracts of Kyrgyzstan plants against three agricultural pests

The 139 extracts from 123 plant species of 38 families of the Kyrgyzstan flora were assessed for their insectoacaricidal and behavior-modifying activities against three species of phytophagous pests: the western flower thrips Frankliniella occidentalis Perg. (Thysanoptera: Thripidae), the twospotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) and the grain aphid Shizaphis graminum Rond. (Homoptera: Aphididae). Western flower thrips larvae were found to be highly tolerant to the plant extracts. The most active extracts against the spider mite were Ailanthus altissima L. (leaves) and roots of Convolvulus krauseanus Regel. and Schmalh., against the grain aphid – of Anabasis aphylla L., roots of Ungernia severtzovii (Regel) B. Fedtsch. and Ferula foetida (Bunge) Regel, and against the thrips – of the Silene sussamyrica Lazkov (aerial part). Extracts from these plants caused significant pest mortality, reduced reproductive potential and deterred pests from feeding on suitable host plants. Extracts of these plants could serve as the foundation for the development of new botanical insecticides.