Reduced Thrips Populations Research Articles

Biological Control and Habitat Management for the Control of Onion Thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), in Onion Production in Quebec, Canada.

Onion thrips (Thrips tabaci) can pose a significant threat to onion crops, causing leaf damage, reduced bulb size and quality, and yield loss during severe infestations. Conventional insecticide use has been the primary method for managing this pest species, but the efficacy of this approach is inconsistent. Furthermore, emerging pest resistance is a growing concern in some regions. This two-year field study aimed to assess the effectiveness of several pest management strategies in controlling onion thrips populations and limiting their impact on onion yields. The strategies tested consisted of habitat manipulations (including flower strips and straw mulch), biological control agents (Stratiolaelaps scimitus, Neoseiulus cucumeris, Amblyseius swirskii, and Beauveria bassiana), as well as physical barrier control methods (exclusion nets, kaolin, and mineral oil). Habitat manipulation techniques, particularly the use of flower strips, reduced thrips populations by up to 50% and increased onion yields by 25%. In contrast, exclusion nets had a detrimental effect on onion yields, and the other alternative control methods produced results comparable to those obtained for untreated controls. When used alone, biological control agents were not effective at maintaining thrips populations below economically damaging levels. This study offers valuable insights into effective and sustainable pest management practices for the onion industry.

Dehydration and tomato spotted wilt virus infection combine to alter feeding and survival parameters for the western flower thrips, Frankliniella occidentalis

Dehydration and tomato spotted wilt virus (TSWV) infection substantially impact the feeding of western flower thrips, Frankliniella occidentalis. Until now, the dynamics between these biotic and abiotic stresses have not been examined for thrips. Here, we report water balance characteristics and changes in other biological parameters during infection with TSWV for the western flower thrips. There were no apparent differences in water balance parameters during TSWV infection of male or female thrips. Our results show that, although water balance characteristics of western flower thrips are minimally impacted by TSWV infection, the increase in feeding and activity when dehydration and TSWV are combined suggests that virus transmission could be increased under periods of drought. Importantly, survival and progeny generation were impaired during TSWV infection and dehydration bouts. The negative impact on survival and reproduction suggests that the interactions between TSWV infection and dehydration will likely reduce thrips populations. The opposite effects of dehydration on feeding/activity and survival/reproduction for virus infected thrips suggest the impact of vectorial capacity will likely be minor for TSWV transmission. As water stress significantly impacts insect-plant-virus dynamics, these studies highlight that all interactions and effects need to be measured to understand thrips-TSWV interactions in their role as viral vector to plants.

Biological control of Western flower thrips, Frankliniella occidentalis using a self-sustaining granular fungal treatment.

Western flower thrips (WFT), Frankliniella occidentalis, is one of the most destructive pests of vegetables, fruits and ornamental crops worldwide, causing extensive damage by direct feeding of the crop and transmitting economically important viruses. Despite the successes of biocontrol agents to control WFT, more efficient and cost-effective ways must be found to encourage grower adoption of integrated pest management. A sustainable fungal treatment was developed to preserve fungal inoculum in potting soil and reduce thrips populations. Combining cooked, oven-dried millet with BotaniGard® (a commercial form of Beauveria bassiana strain GHA) to potting soil increased spore production and persistence of the fungus in the soil. In treated pots with millet, spore concentrations were 3-4 times greater after 30 days compared with spore yields at 10 days. The number of WFT adults was significantly lower in the marigold pots treated with GHA mix + millet than untreated controls, 12% and 10% in treated pots and 70% and 68% in untreated pots in sterile and non-sterile soil, respectively. Incorporation of millet in the potting mix enhanced the effect of the fungal treatments by providing a nutritive substrate on which the fungus could become established. This method is relatively inexpensive and easy for growers to use in greenhouses because granular formulations of B. bassiana are not commercially available.

Evaluation of Tillage, At-Planting Treatment, and Nematicide on Tobacco Thrips (Thysanoptera: Thripidae) and Reniform Nematode (Tylenchida: Hoplolamidae) Management in Cotton

There are numerous early-season pests of cotton, Gossypium hirsutum L., that are economically important, including tobacco thrips, Frankliniella fusca (Hinds), and reniform nematode, Rotylenchulus reniformis (Linford & Oliveira). Both of these species have the potential to reduce plant growth and delay crop maturity, ultimately resulting in reduced yields. A field study was conducted during 2015 and 2016 to evaluate the influence of tillage, at-planting insecticide treatment, and nematicide treatment on pest management, cotton development, and yield. Treatment factors consisted of two levels of tillage (no-tillage and conventional tillage); seven levels of at-planting insecticide treatments (imidacloprid, imidacloprid plus thiodicarb, thiamethoxam, thiamethoxam plus abamectin, acephate plus terbufos, aldicarb, and an untreated control); and two levels of nematicide (no nematicide and 1,3-dichloropropene). There were no significant interactions between tillage, at-planting insecticide treatment, or nematicide for any parameters nor was there a difference in the main effect of nematicide on thrips control or damage. The main effects of tillage and at-planting insecticide treatment impacted thrips densities and damage. The no-tillage treatments and aldicarb in-furrow or acephate seed treatment plus terbufos in-furrow significantly reduced thrips populations. Early-season plant response was impacted by tillage and at-planting insecticide treatment; however, that did not result in significant yield differences. In regard to nematicide treatment, the use of 1,3-dichloropropene resulted in lower yields than the untreated.

Efficacy of insecticides for season-long control of thrips (Thysanoptera: Thripidae) in winter strawberries in Florida

Flower thrips (primarily Frankliniella spp.) can be significant strawberry pests, and recently in Florida, Scirtothrips dorsalis Hood has become an established, early-season, foliar pest. Insecticides that were used for flower thrips management are now also used for S. dorsalis, resulting in the need to evaluate newer insecticides in order to diversify rotations and mitigate overuse of insecticides with the same mode-of-action. We evaluated 10 and 12 season-long insecticide programs in field plots in central Florida during the 2016–2017 and 2017–2018 winter strawberry seasons, respectively. We found that most programs reduced thrips populations and strawberry injury due to thrips feeding, while having limited effects on Orius spp., a primary thrips predator. An early season application of chlorantraniliprole + thiamethoxam, commonly used for other strawberry pests, reduced S. dorsalis populations and strawberry injury, although S. dorsalis populations were relatively low in both study years. When repeat applications of the same insecticide were made throughout the growing season, cyantraniliprole was nearly as effective as spinetoram against Frankliniella spp., while tolfenpyrad and sulfoxaflor did not perform as well. Flupyradifurone was as effective as acetamiprid when used as a follow-up application to spinetoram or cyantraniliprole. Programs including or entirely composed of OMRI-listed insecticides for organic production were not as effective as conventional insecticide programs, with only spinosad providing acceptable thrips control. In conclusion, spinetoram, acetamiprid and spinosad were confirmed to be effective against thrips and can be used as the backbone of rotation programs in conventional and organic strawberry production systems. Diamide insecticides were effective when used repeatedly and in rotation, while flupyradifurone and flonicamid may be used when follow-up applications are needed. Continued research is critical for fine-tuning insecticide programs, with a focus on testing against high S. dorsalis populations in early-planted strawberries and on developing effective sampling methods to optimize timing and reduce the number of applications.

Evaluation of different insecticides for the management of onion thrips (Thrips tabaci Lindeman, 1889) (Thysanoptera, Thripidae) on onion (Allium cepa L.) crops

Abstract The efficacy of five insecticides containing a.i. bifenthrin, dimethoate, spinosad, spinetoram and chlorfenapyr was evaluated following RCBD against Thrips tabaci in farmer’s field for two consecutive years. The data were recorded before and after 24 h, 48 h, 72 h and 7 days of spraying. The results showed that all the insecticides reduced thrips populations compared to controls. However, the maximum reduction in thrips population and highest onion bulb yield (34.07 t/ha) was obtained with dimethoate 40EC followed by bifenthrin 10EC (33.14 t/ha). The minimum onion bulb yield (25.71 t/ha) was obtained in the control, where no insecticide was applied against thrips. If onion thrips are not controlled, the damage they cause can reduce bulb yields by 9-25%. The highest incremental return over the control (Rs.83, 600/ha), net income (Rs.82, 913/ha) and maximum cost benefit ratio were also obtained in the treatment with dimethoate 40EC.

Efficacy of two predatory phytoseiid mites in controlling the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on cherry tomato grown in a hydroponic system

Thrips is one of the most harmful insect groups attacking many field and vegetable crops. Predatory mites, especially those in family Phytoseiidae, are considered as good bioagents to control thrips where application of chemical pesticides can be decreased. This work was conducted to evaluate the efficacy of the two phytoseiid mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans), in controlling the western flower thrips (Frankliniella occidentalis, Pergande) on cherry tomato plants in a hydroponic system. The results indicated that both predatory mites were effective in decreasing populations of adults and larvae of F. occidentalis at all of the chosen periods. The mixed effect of A. swirskii plus N. cucumeris (AS + NC) was higher in reducing thrips populations than that when each of them was used alone. Larvae of F. occidentalis were decreased on leaves of tomato plants from 11.2 and 14.5/leaf in the control treatment (no predatory mites) to 4.27 and 3.73/leaf due to the combination of AS and NC after 7 and 15 days, respectively. On the other hand, larvae of F. occidentalis attained levels of 8.75 and 12.83/five flowers when no predatory mites were applied compared to 2.46 and 1.20/five flowers when adults of AS plus NC were used after 50 and 60 days of releasing, respectively. This study demonstrated that the combination of AS and NC resulted in higher reductions in F. occidentalis without any competition between them.

Efficacy of biorational insecticides against chilli thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae), infesting roses under nursery conditions

AbstractWe evaluated biopesticides based on entomopathogenic fungi, azadirachtin and horticultural oils for the management of the chilli thrips, Scirtothrips dorsalis Hood, an economically significant invasive pest in the United States. Insecticides were applied four times at 7‐ to 10‐day intervals against established S. dorsalis infestations on shrub roses KnockOut®, Rosa x ‘Radrazz’ under simulated nursery conditions. When applied as stand‐alone treatments, Beauveria bassiana GHA (BotaniGard® ES), Metarhizium brunneum F52 (Met‐52 EC), a horticultural oil (SuffOil‐X®) and azadirachtin (Molt‐X®) at label rates provided significant control, reducing populations of S. dorsalis by 48–71% compared with control over 4–6 weeks. Similar results were observed when the biopesticides were applied in rotation with each other. A conventional standard, spinosad (Conserve® SC), was consistently the most effective treatment in these studies, reducing thrips populations by >95% overall. In another study, more effective control (87%–92%) was achieved in biopesticide rotation programmes that included spinosad, when compared with those that did not. Results also showed that these biopesticides can be tank‐mixed. However, there was no evidence that B. bassiana or M. brunneum combined with azadirachtin resulted in additive or synergistic control, as neither tank‐mix treatment improved control compared with azadirachtin alone. These findings highlight the potential use of biopesticides in rotation programmes with conventional insecticides to manage S. dorsalis on roses. Biopesticides evaluated in this study can be incorporated into an IPM programme for roses.

Phorate‐induced Host Defence Responses Condition Acquired Resistance to Tomato Spotted Wilt in Cultivated Peanut (Arachis hypogaea L.)

AbstractPhorate is an acetylcholinesterase‐inhibiting organophosphate pesticide used for the control of insects, mites and nematodes. In cultivated peanut (Arachis hypogaea L.), phorate is often used as an in‐furrow, systemic insecticide to reduce thrips populations which vector tomato spotted wilt tospovirus (TSWV). However, phorate‐induced suppression of disease incidence and severity is not solely due to thrips control because other pesticides control thrips but not TSWV. The present research was focused on understanding the biochemical and molecular components of the phorate‐induced host responses that may condition acquired resistance to TSWV in peanut. Phorate treatments adversely affected maximal quantum yield of the light reactions (Fv/Fm). A dose‐dependent increase in ascorbic acid content and in activities of the oxidative stress‐related enzymes, catalase and superoxide dismutase was evident following phorate treatment, whereas the level of glutathione reductase was not affected. An RT‐PCR differential display screen identified 35 expressed sequence tags (ESTs) responsive to phorate treatment in peanut leaves. Functional annotations revealed transcriptional regulation of ESTs implicated in primary and secondary metabolism including photosynthesis‐related genes, mitigation of oxidative stress, signalling pathways and pathogenesis‐ and defence‐related proteins. Two ESTs encoding membrane trafficking functions were downregulated, which may reflect reduced internalization and/or subsequent replication of viral particles in phorate‐treated leaves. Time‐course quantitative RT‐PCR analyses further verified fidelity and sensitivity of the mRNA differential display screen and corroborated that systemic spread of TSWV in field‐grown plants is reduced following phorate application. The mélange of differentially regulated gene functions is consistent with a model in which a phorate‐induced breach of redox control culminates in hypersensitive cell death and subsequent induction of systemic acquired resistance.

Evaluation of Entomopathogenic Fungi Against Chilli Thrips,Scirtothrips dorsalis

Commercial strains of entomopathogenic fungi were evaluated for control of chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), an invasive pest of ornamental and vegetable plants in the Caribbean and southeastern United States. In laboratory assays, LC50 values against adult S. dorsalis were 5.1 × 104 CFU/mL for Beauveria bassiana GHA, with higher values 3.1 × 105 for Metarhizium brunneum F52 and 3.8 × 105 for Isaria fumosorosea Apopka 97. Second instars were comparatively less susceptible to all isolates, ostensibly due to moulting, with LC50 values of 1.1 × 108, 7.0 × 105, and 9.9 × 105 CFU/spores per mL for GHA, F52, and Apopka 97 strains, respectively. In greenhouse cages, compared with controls, three applications of mycoinsecticides and other biorational insecticides at 7 to 14 day intervals reduced overall S. dorsalis populations on pepper plants Capsicum annuum cv. California Wonder: spinosad reduced populations by 94–99%, M. brunneum F52 by 84–93%, B. bassiana GHA by 81–94%, I. fumosorosea PFR-97 by 62–66%, and different horticultural oils by 58–85%. The proportion of marketable fruit was significantly increased by M. brunneum F52, B. bassiana GHA, and 2% SuffOil-X treatments. Slightly lower levels of control were observed in nursery tests with ornamental rose shrubs, Rosa sp. Red Double Knock Out®, during hot sunny conditions. Four applications reduced thrips populations over 10 weeks: spinosad by an average of 91%, M. brunneum F52 by an average of 81%, B. bassiana GHA by an average of 62%, SuffOil-X by an average of 50%, and I. fumosorosea PFR-97 by an average of 44%. The data show that mycoinsecticides can be used in management strategies for low to moderate populations of S. dorsalis and provide resistance management tools for the limited number of insecticides that are effective against this pest.

Flower model traps reduced thrips infestations on a pepper crop in field

A flower model trap developed by modifying an artificial yellow chrysanthemum flower was more attractive to flower thrips than commercial yellow sticky traps. Installation of these flower model traps (20 traps per 50m2 plot) was reported to reduce seasonal populations of Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) on strawberry flowers in greenhouses. In this study, we sought to determine if the installation of such flower model traps would reduce thrips populations in a pepper field. The traps were installed at the bottom of the plant canopy at varying densities (0, 5, 10, and 20 traps) in 20 plots (each 3×5m2) using a completely randomized design. Thrips populations on pepper flowers were sampled from 1 to 29 July in 2009. All thrips sampled on the flowers were identified as F. intonsa. A significant effect of treatment and sampling date was found from repeated-measure analysis of variance. The highest density (20 traps per 15m2) of traps significantly reduced the female and male F. intonsa population compared to the control by 61 and 49%, respectively. However, no difference in immature thrips numbers was found among the treatments. These results indicate that this flower model trap can be a useful tool for the management of flower thrips on field-grown peppers.

Biological control-based IPM in sweet pepper greenhouses using Amblyseius swirskii (Acari: Phytoseiidae)

The predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) has been evaluated as a potential biological control agent for whitefly and thrips, but it has yet to be demonstrated that the addition of A. swirskii to an existing biological control programme improves management of these pests in commercial greenhouses. Experiments were initiated at the beginning of the cropping season in greenhouses located in the two main sweet pepper growing areas of Spain. At each location, a randomised complete block design was used with four replicates and two treatments: (1) current biological control-based Integrated Pest Management standard or (2) this standard supplemented by introductions of A. swirskii. A. swirskii established and reproduced well in the crop and was the most abundant phytoseiid species during the experiment in the plots where it was released. It also provided significant reduction of the whitefly population and pest control costs compared to greenhouses employing the standard. However, the addition of A. swirskii did not reduce thrips populations with respect to plots not receiving the predatory mite, presumably due to the inclusion of the anthocorid bug Orius laevigatus Fieber (Heteroptera: Anthocoridae) which established well. These results make the inclusion of A. swirskii in IPM programmes for sweet pepper crops advisable for whitefly control.

Efficacy of neem oil against thrips (Thysanoptera) on mango panicles and its compatibility with mango pollinators

A field trial was conducted in a mango (Mangifera indica L.) orchard located on Penang Island, Malaysia, to determine the efficacy of neem oil at 1, 2 and 3% concentrations and imidacloprid, a commonly used synthetic insecticide, on populations of thrips and their toxicities to mango pollinators. Daily periodicities of several pollinators that frequently visited mango panicles were studied prior to the insecticide trial to determine the appropriate time of insecticide application. Pollinators were collected at 2-h intervals for 2 months in the dry season and 1 month in the wet season of 2009. Mean numbers of all pollinators were greater in the morning (0800 h) and peaked in the late afternoon, but remained low during other times of the day. After two consecutive applications at 7-day interval, both neem oil and imidacloprid effectively reduced thrips populations compared to an untreated plot. Imidacloprid was the most effective insecticide reducing 68.7% thrips adult and 80.7% larval populations, respectively. However, it caused 92.5% mortality in pollinator populations. Neem oil at 2% was effective against adult thrips 96 h after the second application (59.8% reduction) and caused only 24.9% mortality of pollinators. Proper timing of neem oil application such as at midday when pollinators are least active would control thrips populations satisfactorily but less detrimental to mango pollinators. Future improvement of neem oil formulation should be aimed at improving its efficacy against thrips and further reducing toxicity to pollinators.

Evaluation of Montandoniola confusa Streito and Matocq sp. nov. and Orius insidiosus Say (Heteroptera: Anthocoridae), for control of Gynaikothrips uzeli Zimmerman (Thysanoptera: Phlaeothripidae) on Ficus benjamina

Since its discovery in Florida in 2003, the weeping fig thrips, Gynaikothrips uzeli Zimmerman has spread rapidly throughout the southeastern United States in shipments of ornamental Ficus benjamina L. Concurrently, there have been reports of an invasive anthocorid, Montandoniola confusa (= moraguesi) Streito and Matocq sp. nov., widely associated with G. uzeli populations in landscape plantings of ornamental Ficus spp. We evaluated M. confusa and a commercially available anthocorid, Orius insidiosus Say, as biological control agents of G. uzeli. Prey preference studies revealed that eggs were the numerically preferred host stage for both predator species (representing 92% and 94% of all prey taken in ‘no choice’ and ‘choice’ tests, respectively). Females of both predator species consumed significantly more eggs than males (83–91 versus 25–35 per 48 h period, respectively), and (in the absence of eggs) also more larvae (4.1–5.5 versus 2.1–2.5). Fecundity of M. confusa was significantly higher than for O. insidious, 10.6 ± 1.5 eggs per 48 h versus 5.0 ± 1.4, respectively. Greenhouse tests on heavily infested F. benjamina revealed that M. confusa was a highly effective predator of G. uzeli. Evaluations with three F. benjamina cultivars showed that M. confusa reproduced throughout the year and reduced thrips populations ⩾95% and leaf galls by up to 77% within 5 weeks. By contrast O. insidiosus did not establish or significantly reduce populations of G. uzeli inside leaf galls. Methods to monitor and protect M. confusa in urban landscapes are discussed.

Bronzing of Strawberry Fruit as Affected by Production Practices, Environmental Factors, and Thrips

Strawberry fruit are subject to three different types of bronzing damage that cause discoloration of the fruit surface and loss of market quality. Type I and Type II bronzing both occur in localized areas of the fruit and are caused by arthropod feeding and chemical phytotoxicity, respectively. In contrast, Type III bronzing (T3B) covers the entire fruit and is associated with environmental and plant stress factors, although many growers and crop advisers believe that T3B is caused by thrips feeding. The purpose of our 3-year study was to investigate incidence of T3B as affected by crop management practices and thrips populations. Replicated field trials demonstrated that overhead cooling with sprinklers resulted in a significant reduction in T3B incidence. In addition, a series of foliar pesticide spray applications also resulted in reduced T3B damage to strawberry fruit. Foliar applications of Thiolux sulfur, other registered pesticides, and lignin products all resulted in reduced incidence of T3B in field trials. In contrast, T3B incidence was not associated with thrips populations; insecticide-treated plots had reduced thrips populations and comparable T3B incidence to nontreated plots that had greater thrips populations. Our study provides evidence that T3B occurrence is associated with exposure to elevated temperatures and solar radiation rather than thrips feeding and that growers can reduce T3B incidence by implementing production practices that reduce plant stress and protect fruit from radiation damage.

Interactions between Orius albidipennis (Heteroptera: Anthocoridae) and Neoseiulus cucumeris (Acari: Phytoseiidae): Effects of host plants under microcosm condition

In three-dimensional microcosm set-ups we explored the influence of host plant traits of cucumber, eggplant and sweet pepper on the interactions between minute pirate bugs, Orius albidipennis (Reuter) and predatory mites, Neoseiulus cucumeris (Oudemans) in the presence of extraguild prey, Thrips tabaci Lindeman. The host plant influenced the population development of thrips with sweet pepper being most inferior and cucumber being the best for egg laying and/or juvenile development and survival. No host plant effect was found on the survival of adult thrips. The host plant also influenced the biocontrol efficiency of O. albidipennis which, on its own, significantly reduced thrips populations on sweet pepper and eggplant, but not on cucumber. A similar host plant effect was not seen for N. cucumeris which, on its own, was unable to reduce thrips populations on either of the host plants. No additive or synergistic effect between the two predators was observed. Finally, the host plant influenced the interactions between the two predators—when both predators were present, a significant reduction in the density of adult mites was observed on cucumber and sweet pepper, presumably a result of intraguild predation from O. albidipennis. No influence of O. albidipennis on the predatory mites was found on eggplant and on none of the host plants was a negative influence observed on mite eggs or nymphs. The results point to the importance of including host plant aspects in studies aimed at evaluations of possible interactions between beneficials intended for simultaneous applications for biocontrol.

Manipulating fertilization: a management tactic against Frankliniella occidentalis on potted chrysanthemum

AbstractFertilization during production of greenhouse chrysanthemum, Dendranthema grandiflora (Tzvelev), will influence Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) populations as well as plant productivity and postproduction longevity. It is essential to include fertilization effects in the development of crop management practices that reduce thrips populations and maintain plant marketability. In this study, we lowered fertilization to reduce thrips population abundance while maintaining plant productivity. We tested fertilization levels below and above the recommended level (375 p.p.m. N) for commercial production. We reduced mean rate of change in F. occidentalis abundance from 0.05 to 0.03 (day−1) and mean number of thrips per plant by 44% by fertilizing with either 188 p.p.m. N (50% of the recommended level) or 568 p.p.m. N (150%) and higher. Fertilization influenced not only the rate of change in thrips abundance but also the production time (from transplanting to flower opening). Lowering fertilization to 50% of the recommended level lengthened mean production time from 84 to 88 days. Plant height, flower size, and flower number were not adversely affected when fertilization was reduced to 50% of the recommended level. Mean postproduction longevity was shortened from 26 to 24 days when plants were fertilized with 50% of the recommended level. Two important advantages of lowering fertilization to 50% of the recommended level were (1) a 44% reduction in mean F. occidentalis abundance and (2) a significant reduction in fertilizer input for the production system. Manipulation of fertilization can be a useful management tactic against F. occidentalis.

Incidence of Thrips and Tomato Spotted Wilt <I>Tospovirus</I> in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations

The relative impacts of early season thrips exclusion (cages) and thrips suppression (pesticides) on tomato spotted wilt (family Bunyaviridae, genus Tospovirus, TSW) Tospovirus infection in flue-cured tobacco, Nicotiana tobaccum L., were examined in field trials in 2001-2004. There were fewer TSW symptomatic plants when plants were covered by exclusion cages for 6 wk than when they were uncaged or caged for 2 or 4 wk after transplanting. Plant height, leaves per plant, and total leaf weight per plant were lower in TSW symptomatic plants compared with nonsymptomatic plants for the uncaged plus 2- and 4-wk caged duration treatments but not different when caged 6 wk. Weekly acephate (Orthene) foliar sprays for 2 or 4 wk after transplanting reduced thrips populations for up to 5 wk after transplanting, whereas the 6-wk sprays had lower thrips populations for up to 8 wk. TSW was lower in both the 4- and 6-wk acephate treatments than in the untreated. A tray drench application of imidacloprid (Admire) reduced thrips populations in early season plus lowered the percentage of TSW compared with no tray drench treatment. The tobacco thrips, Frankliniella fusca (Hinds), was the predominate thrips species on tobacco foliage, and 1.9-4.9% tested positive for nonstructural TSW protein. The imidacloprid tray drench treatment and 6-wk acephate foliar sprays had lower densities of the tobacco-adapted form of Myzus persicae (Sulzer). Suppressing early season thrips populations with foliar acephate or imidacloprid tray drench are management option that can effectively reduce the incidence of TSW in flue-cured tobacco plus suppress aphids.

Simultaneous application of entomopathogenic nematodes and predatory mites to control western flower thrips Frankliniella occidentalis

Abstract Effects of entomopathogenic nematodes alone (Heterorhabditis bacteriophora Poinar or H. indica Poinar, Karunakar, and David), a predatory mite species alone [Amblyseius cucumeris (Oudemans) (Acarina: Phytoseiidae)], or the combination of nematodes and mites for the control of the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) was investigated in a climate controlled growth chamber and greenhouse. Different densities and concentrations of mites and nematodes, respectively, were tested at different densities of thrips infesting beans (Phaseolus vulgaris L.). In the growth chamber experiment, the presence of mites on the plants resulted in a large number of second-instar larvae of thrips to fall off the plants and to pupate in the soil, thereby increasing the number of available host larvae for the nematodes to attack. Applications of mites or nematodes alone, or combined applications of both natural enemies always resulted in greater thrips reduction than control treatment. Introduction of 10 adult mites per plant and applications of 200 infective juveniles (IJs) cm−2 of nematodes resulted in up to 83% thrips control, which was significantly higher than individual applications of each natural enemy. Due to high summer temperatures and low relative humidity, weekly applications of nematodes at 50 IJs cm−2 failed to control thrips in the greenhouse experiment. Yet, weekly applications of nematodes alone at 200 IJs cm−2, mites alone at three adults per plant, or the combined application of the natural enemies at these rates significantly reduced thrips populations. Thus, this study clearly shows a great potential of combined applications of the mites and the nematodes to control foliage-feeding and soil-dwelling life stages of thrips.

Nitrogen, Aldicarb, and Cover Crop Effects on Cotton Yield and Fiber Properties

Thrips, primarily Frankliniella spp., can damage cotton (Gossypium hirsutum L.) seedlings. The objectives of this study were to determine the effect of winter cover crops on thrips populations in cotton and to assess the yield and fiber quality response to cover crops and N fertilizer rate with and without thrips protection. A field experiment was conducted on a Bonneau loamy sand soil (loamy, siliceous, thermic, Arenic Paleudult) from 1996 through 1998. Treatments were cover crops, N fertilizer rate, and aldicarb rate. Cover crops were rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), a clover + rye mixture, and winter fallow. Nitrogen levels were 0, 78, and 112 kg N ha−1. Aldicarb levels were 0 and 1.18 kg a.i. ha−1. Aldicarb reduced thrips populations. For plots without aldicarb, differences among winter covers occurred at one sampling time in 1998 when fallow had more thrips than the other three winter covers. Aldicarb increased yield by 9% in 1996, 48% in 1997, and 35% in 1998. In 1997 and 1998, yield increases with aldicarb were greater in the winter cover and N treatment combinations that provided higher total N to the crop. The 0 kg N ha−1 rate tended to have lower yield, fiber length, length uniformity, fiber strength, micronaire, and Hunter's +b than the other two N rates. Aldicarb generally increased the value of these fiber properties each year. Including agronomic practices in assessing control measures may improve integrated pest management strategies for thrips in conservation tillage systems.