Onion Thrips (Thysanoptera: Thripidae) and Their Management in the Treasure Valley of the Pacific Northwest

Onion thrips, Thrips tabaci Lindeman and thrips-transmitted Iris yellow spot virus are the most significant pest complex affecting onion production in the Treasure Valley of eastern Oregon and southwestern Idaho. Thrips feeding damage and virus infection significantly reduce onion bulb size and economic returns for this high value crop. The high concentration of onion fields in the Treasure Valley and the long, hot, dry growing season present a number of challenges for managing onion thrips and Iris yellow spot virus (IYSV). Insecticides are the primary tool that growers have to manage this pest complex. With the long growing season, growers need to exercise good insecticide resistance management programs to maintain the effectiveness of currently available insecticides. To do this, growers need to rotate among available products and use as few applications as practical. A challenge for researchers is to determine not only which insecticides are effective but also to determine when during the season different products may be most effectively used. Techniques for analyzing field trial data are discussed, including comparing changes in pest populations before and after various insecticide applications are made. These comparisons can be made through the use of linear estimates and contrasts as part of analyses of variance, and they can aid in determining efficacy of different treatments by accounting for pre-application populations. These techniques will help researchers in developing sound sequence of insecticide applications for onion thrips management.Keywords: Yellow Spot Virus, IPM, pest management, analysis of variance, insecticide resistance management, Onion thrips, linear contrast

Host preference of Thrips hawaiiensis for different ornamental plants

AbstractThrips hawaiiensis is a common thrips pest that damages the flowers of various plants. The differing population sizes of T. hawaiiensis among host plants suggest its preference and performance vary among host plants. In this study, the host fitness of T. hawaiiensis for different flowers was assessed through field investigation. The behavioral responses of T. hawaiiensis to the color and volatiles of flowers eliciting different apparent fitness levels and their development and survival on the plants were also studied. Adults and larvae of T. hawaiiensis were found in the flowers of 21 species, which were classified into four fitness levels for this thrips species. T. hawaiiensis showed significantly different visual responses to the color and olfactory responses to the volatiles of four tested flowers (each representing one of the four fitness levels), with the rankings of visual preferences for Dianthus caryophyllus > Tulipa gesneriana > Hydrangea macrophylla > Rosa rugosa, and olfactory preferences for H. macrophylla ≥ T. gesneriana > D. caryophyllus > R. rugosa. Plant species had significant influences on the development and survival of T. hawaiiensis, with developmental times from egg to adult of 9.58 d, 9.92 d, 10.35 d and 10.75 d on H. macrophylla, T. gesneriana, D. caryophyllus and R. rugosa, respectively, and corresponding survival rates of 76.33%, 71.33%, 64.00% and 59.00%. In summary, this study shows that olfactory preferences were consistent with the field performance of T. hawaiiensis on the four flower plants tested. Further, fitness levels of host plant flowers are correlated with development rate and survivorship of T. hawaiiensis. Our study adds to the understanding of the mechanism of host selection by thrips and provides basic information to underpin the management of T. hawaiiensis on horticultural plants

Production of microsclerotia of the fungal entomopathogen Lecanicillium lecanii (Hypocreales: Cordycipitaceae) as a biological control agent against soil-dwelling stages of Frankliniella occidentalis (Thysanoptera: Thripidae)

Microsclerotia (MS) production by two isolates of Lecanicillium lecanii on various culture media is described, and the efficacy of MS against western flower thrips is evaluated. High concentrations of MS (2.9-3.1×10⁵•mL⁻¹) were produced in media with C: N ratios of 7.4:1 and 10.3:1 by isolate SN21. Bioassays using soil-incorporated MS resulted in significant infection and mortality of thrips.Keywords: Frankliniella occidentalis, Lecanicillium lecanii, fermentation, integrated biological pest control, microscleroti

Impacts on Natural Enemies and Competitor Thrips of Insecticides against the Western Flower Thrips (Thysanoptera: Thripidae) in Fruiting Vegetables

Newer, selective insecticides with few negative impacts on natural enemies and competitor species are needed for effective, sustainable management of the western flower thrips, Frankliniella occidentalis (Pergande). The purpose of this study was to evaluate the impacts on natural enemies and competitor thrips species of insecticides used for control of western flower thrips in fruiting vegetables. Trials with tomato (Solanum lycopersicum L.) and with pepper (Capsicum annuum L.) were conducted to evaluate insecticide treatment effects on western flower thrips and natural enemies at the North Florida in 2008, 2009, 2010 and 2011. A number of insecticides from different classes showed moderate to high efficacy against western flower thrips. The broad-spectrum insecticides acetamiprid, methomyl, and tolfenpyrad demonstrated activity against the pest, while also reducing populations of the key predator of thrips in pepper, Orius insidiosus (Say) (Hemiptera: Anthocoridae). Insecticides that showed little impact on populations of O. insidiosus were cyantraniliprole, flonicamid, spirotetramat, and terpenes. Although only moderately active against the western flower thrips, they would be valuable additions to existing management programs for pepper. Insecticides with activity against western flower thrips also showed activity against Frankliniella tritici (Fitch). This non-damaging congener species is a beneficial because it out-competes the western flower thrips, especially in tomato where O. insidiosus is not a major factor in western flower thrips management. Numerous insecticides were identified with activity against the western flower thrips that are suitable for use in integrated pest management programs of fruiting vegetables.Keywords: Pepper, Biological insecticides, Biological control, Reduced-risk insecticides, Orius, Tomat

Frankliniella occidentalis (Pergande) integrated pest management programs for fruiting vegetables in Florida

BACKGROUND: The spread of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), resulted in the worldwide destabilization of established integrated pest management programs for many crops. Efforts to control the pest and the thrips-vectored tospoviruses with calendar applications of broad-spectrum insecticides have been unsuccessful. The result has been a classic ‘3-R’ situation: resistance to numerous insecticides; resurgence of the western flower thrips populations as a result of natural predators and native competitor thrips being eliminated; replacement by various other pests. This paper reports on integrated pest management programs for fruiting vegetables that are effective, economical, ecologically sound and sustainable. RESULTS: The components include the following: define pest status (economic thresholds); increase biotic resistance (natural enemies and competition); integrate preventive and therapeutic tactics (scouting, ultraviolet-reflective technologies, biological control, compatible insecticides, companion plants and fertility); vertically integrate the programs with other pests; continually communicate latest science-based management tactics with end-users. CONCLUSION: These programs have been widely implemented in Florida and have significantly improved the management of western flower thrips and thrips-transmitted viruses.This is the publisher’s final pdf. The article is copyrighted by the Society of Chemical Industry and published by John Wiley & Sons, Inc. It can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291526-4998Keywords: thrips, fruiting vegetables, tospovirus, integrated pest management, Frankliniella occidentali

Does Temperature-Mediated Reproductive Success Drive the Direction of Species Displacement in Two Invasive Species of Leafminer Fly?

Liriomyza sativae and L. trifolii (Diptera: Agromyzidae) are two highly invasive species of leafmining flies, which have become established as pests of horticultural crops throughout the world. In certain regions where both species have been introduced, L. sativae has displaced L. trifolii, whereas the opposite has occurred in other regions. These opposing outcomes suggest that neither species is an inherently superior competitor. The regions where these displacements have been observed (southern China, Japan and western USA) are climatically different. We determined whether temperature differentially affects the reproductive success of these species and therefore if climatic differences could affect the outcome of interspecific interactions where these species are sympatric. The results of life table parameters indicate that both species can develop successfully at all tested temperatures (20, 25, 31, 33°C). L. sativae had consistently higher fecundities at all temperatures, but L. trifolii developed to reproductive age faster. Age-stage specific survival rates were higher for L. sativae at low temperatures, but these were higher for L. trifolii at higher temperatures. We then compared the net reproductive rates (R₀) for both species in pure and mixed cultures maintained at the same four constant temperatures. Both species had significantly lower net reproductive rates in mixed species cultures compared with their respective pure species cultures, indicating that both species are subject to intense interspecific competition. Net reproductive rates were significantly greater for L. sativae than for L. trifolii in mixed species groups at the lower temperatures, whereas the opposite occurred at the higher temperature. Therefore, interactions between the species are temperature dependent and small differences could shift the competitive balance between the species. These temperature mediated effects may contribute to the current ongoing displacement of L. sativae by the more recent invader L. trifolii in warm climatic areas of China

Variation within and between Frankliniella Thrips 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

Molecular Survey for the Invasive Leafminer Pest Liriomyza huidobrensis (Diptera: Agromyzidae) in California Uncovers Only the Native Pest Liriomyza langei

Liriomyza huidobrensis (Blanchard) is a highly destructive invasive leafminer pest currently causing extensive damage to vegetable and horticultural crops around the world. Liriomyza langei Frick is a leafminer pest native to California that cannot currently be morphologically distinguished from L. huidobrensis. We used a DNA-barcoding approach, a published PCR-RFLP method, and a new multiplex PCR method to analyze 664 flies matching the morphological description of huidobrensis-langei. We found no evidence for the presence of L. huidobrensis in our extensive samples from California. In addition to the new molecular method, this work is important because it provides definitive data that the California “pea leafminer” is currently, and has probably always been, L. langei. These data will also be important in the event that the highly invasive L. huidobrensis ever becomes established.Keywords: molecular diagnostics, crop pest, invasive species, multiplex PC