Seasonal abundance of thrips (Thysanoptera) in capsicum and chilli crops in south-east Queensland, Australia

Thrips can be important pests of capsicum and chilli crops, causing damage through their feeding and by vectoring viral diseases. As different species vary in their ability to transmit viruses and in their susceptibility to insecticides, it is important to know which species are present in a crop. The seasonal occurrence of thrips in capsicum and chilli crops in the Bundaberg district of south-east Queensland was investigated from July 2002 to June 2003. Fifty flowers were collected weekly from crops on seven farms and the adult thrips extracted and identified. Thrips palmi Karny and Frankliniella occidentalis (Pergande) were collected in the greatest numbers, with T. palmi predominant in autumn crops (March to July) and F. occidentalis predominant in spring crops (August to November). Pseudanaphothrips achaetus (Bagnall) was common, while Thrips tabaci Lindeman, Thrips imaginis Bagnall and Frankliniella schultzei (Trybom) were collected in low numbers.

Tobacco Streak Virus in cotton-scoping study

In 2006, Tobacco streak virus (TSV) was identified as the causal agent of the devastating sunflower necrosis disease in central Queensland (CQ), and subsequently in 2007 as the cause of major losses in mungbeans in the same area. It has been a major factor in the recent downturn in the sunflower industry in CQ. Surveys in 2007/2008 as part of a one year scoping study (project 03DAQ005) found TSV in cotton in CQ. The symptoms were mostly confined to the feeding sites of the thrips and appeared as reddish spots and rings, but only occasionally the plants were systemically infected and showed a chlorotic mosaic and leaf deformation. The major objectives of this project (DAQ0002) were to determine: the incidence and distribution of TSV in cotton and its likely effect on yield; the thrips vector species associated with TSV infections in cotton; and the factors that may lead to systemic infections. In contrast to the extensive damage observed in sunflower and mungbean crops from the same region, TSV has caused no measurable damage in commercial cotton crops surveyed in CQ over the seasons 2008/9 to 2010/11. No TSV infected cotton was found in regions outside of CQ and the geographical distribution of TSV disease in cotton (and other susceptible hosts) appears to be closely related to the distribution of the major alternative host, parthenium weed. The most likely thrips species responsible for transmission of TSV into cotton is the tomato thrips (Frankliniella schultzei) and onion thrips (Thrips tabaci). Systemically infected plants are rarely seen in commercial crops and have also been rarely produced in controlled tests. It appears that systemic infection may be transient with only mild symptoms being produced intermittently. With current cultivars and conditions, it appears likely that TSV will continue to cause only minor levels of mild local lesions with no impact on yield in cotton crops. It appears that no specific control strategies are required to limit the impact of TSV in cotton. However, general farm hygiene to minimise the presence of the major alternative host of TSV, parthenium weed, is advised and may be of vital importance if TSV susceptible rotational crops such as mung beans are grown.

Thrips incidence in green beans and the degree of damage caused

Green bean production accounts for 2.4% of the total value of Australian vegetable production and was Australia's tenth largest vegetable crop in 2008-2009 by value. Australian green bean production is concentrated in Queensland (51%) and Tasmania (34%) where lost productivity as a direct result of insect damage is recognised as a key threat to the industry (AUSVEG, 2011). Green beans attract a wide range of insect pests, with thrips causing the most damage to the harvestable product, the pod. Thrips populations were monitored in green bean crops in the Gatton Research Facility, Lockyer Valley, South-east Queensland, Australia from 2002-2011. Field trials were conducted to identify the thrips species present, to record fluctuation in abundance during the season and assess pod damage as a direct result of thrips. Thirteen species of thrips were recorded during this time on bean plantings, with six dominant species being collected during most of the growing season: Frankliniella occidentalis, F. schultzei, Megalurothrips usitatus, Pseudanaphothrips achaetus, Thrips imaginis and T. tabaci. Thrips numbers ranged from less than one thrips per flower to as high as 5.39 thrips per flower. The highest incidence of thrips presence found in October/November 2008, resulted in 10.74% unmarketable pods due to thrips damage, while the lowest number of thrips recorded in April 2008 caused a productivity loss of 36.65% of pods as a result of thrips damage.

Floating row covers and pyriproxyfen help control silverleaf whitefly Bemisia tabaci (Gennadius) Biotype B (Homoptera: Aleyrodidae) in zucchini

In zucchini, the use of row covers until flowering and the insect growth regulator (IGR) pyriproxyfen are effective methods of reducing the number of insects, especially silverleaf whitefly (Bemisia tabaci (Gennadius) Biotype B), on plants. We compared floating row covers (FRCs) up until flowering with silverleaf whitefly (SLW) introduced (FRC + SLW), or not introduced (FRC-only), or with introduction of SLW in open plots (SLW-only), or with introduction of SLW in open plots with IGR (SLW + IGR). FRC increased temperature and humidity compared with the uncovered treatments. Average fruit weight was less (P < 0.01) for the FRC + SLW treatment compared with the other treatments and the percentage of marketable fruit was less for the FRC + SLW than for the other three treatments. This result indicates that the use of either row covers or IGR controls whiteflies, reduces fruit damage and increases the size, weight, and quality of fruit, and may also control other sap-sucking insects. However, if SLW are already present on plants, the use of FRC may reduce predation and favour build up of SLW. Thus, FRC and IGR, if used judiciously, may provide an effective alternative to broad-spectrum pesticides in small-scale cucurbit production.

Sampling and management of Bemisia tabaci (Genn.) biotype B in Australian cotton

Data on seasonal population abundance of Bemisia tabaci biotype B (silverleaf whitefly (SLW)) in Australian cotton fields collected over four consecutive growing seasons (2002/2003-2005/2006) were used to develop and validate a multiple-threshold-based management and sampling plan. Non-linear growth trajectories estimated from the field sampling data were used as benchmarks to classify adult SLW field populations into six density-based management zones with associated control recommendations in the context of peak flowering and open boll crop growth stages. Control options based on application of insect growth regulators (IGRs) are recommended for high-density populations (>2 adults/leaf) whereas conventional (non-IGR) products are recommended for the control of low to moderate population densities. A computerised re-sampling program was used to develop and test a binomial sampling plan. Binomial models with thresholds of T=1, 2 and 3 adults/leaf were tested using the field abundance data. A binomial plan based on a tally threshold of T=2 adults/leaf and a minimum sample of 20 leaves at nodes 3, 4 or 5 below the terminal is recommended as the most parsimonious and practical sampling protocol for Australian cotton fields. A decision support guide with management zone boundaries expressed as binomial counts and control options appropriate for various SLW density situations is presented. Appropriate use of chemical insecticides and tactics for successful field control of whiteflies are discussed.

Analysing industry needs to fine tune IPM project activities

As a first step to better targeting the activities of a project for improving management of western flower thrips, Frankliniella occidentialis, (WFT) in field grown vegetable crops, we surveyed growers, consultants and other agribusiness personnel in two regions of Queensland. Using face-to-face interviews, we collected data on key pests and measures used to manage them, the importance of WFT and associated viral diseases, sources of pest management information and additional skills and knowledge needed by growers and industry. Responses were similar in the two regions. While capsicum growers in one northern Queensland district had suffered serious losses from WFT damage in 2002, in general the pest was not seen as a major problem. In cucurbit crops, the silverleaf whitefly (Bemisia tabaci biotype B) was considered the most difficult insect pest to manage. Pest control tactics were largely based on pesticides although many respondents mentioned non-chemical methods such as good farm hygiene practices, control of weed hosts and regular crop monitoring, particularly when prompted. Respondents wanted to know more about pest identification, biology and damage, spray application and the best use of insecticides. Natural enemies were mentioned infrequently. Keeping up to date with available pesticide options, availability of new chemicals and options for a district-wide approach to managing pests emerged as key issues. Growers identified agricultural distributors, consultants, Queensland Department of Primary Industries staff, other growers and their own experience as important sources of information. Field days, workshops and seminars did not rank highly. Busy vegetable growers wanted these activities to be short and relevant, and preferred to be contacted by post and facsimile rather than email. In response to these results, we are focusing on three core, interrelated project extension strategies: (i) short workshops, seminars and farm walks to provide opportunities for discussion, training and information sharing with growers and their agribusiness advisors; (ii) communication via newsletters and information leaflets; (iii) support for commercialisation of services.

Pyriproxyfen controls silverleaf whitefly, Bemisia tabaci (Gennadius), biotype B (Homoptera: Aleyrodidae) (SLW) better than buprofezin in bitter melons Momordica charantia L. (Cucurbitaceae)

To improve compatibility between chemical and biological controls, the use of selective insecticides such as insect growth regulators (IGRs) is crucial. In cucurbits, the use of pyriproxyfen (an IGR) has been shown by others to be an effective method of reducing the number of sap-sucking insects, especially silverleaf whitefly, Bemisia tabaci (Gennadius) Biotype B (SLW). Therefore, we compared pyriproxyfen and buprofezin (an IGR) with that of no treatment (control) in a bitter melon crop for the control of populations of SLW and for their effects on fruit production. Pyriproxyfen controlled SLW and tended to have heavier fruits than the control treatment and reduced the abundance of nymphs and exuvia. Buprofezin showed no evidence in controlling SLW compared with the pyriproxyfen and control treatments. Neither pyriproxyfen nor buprofezin had any effect on the number of harvested fruit or overall fruit yield, but the average weight per fruit was higher than the control treatment. Pyriproxyfen was effective in controlling whitefly populations in bitter melons, and both pyriproxyfen and buprofezin may have the potential to increase yield. Their longer-term use may increase predation by natural enemies as they are species-specific and could favour build up of natural enemies of SLW. Thus, the judicious use of pyriproxyfen may provide an effective alternative to broad-spectrum insecticides in small-scale cucurbit production.

Inter-seasonal population dynamics and pest status of Bemisia tabaci (Gennadius) biotype B in an Australian cropping system

Bemisia tabaci, biotype B, commonly known as the silverleaf whitefly (SLW) is an alien species that invaded Australia in the mid-90s. This paper reports on the invasion ecology of SLW and the factors that are likely to have contributed to the first outbreak of this major pest in an Australian cotton cropping system, population dynamics of SLW within whitefly-susceptible crop (cotton and cucurbit) and non-crop vegetation (sowthistle, Sonchus spp.) components of the cropping system were investigated over four consecutive growing seasons (September-June) 2001/02-2004/05 in the Emerald Irrigation Area (EIA) of Queensland, Australia. Based on fixed geo-referenced sampling sites, variation in spatial and temporal abundance of SLW within each system component was quantified to provide baseline data for the development of ecologically sustainable pest management strategies. Parasitism of large (3rd and 4th instars) SLW nymphs by native aphelinid wasps was quantified to determine the potential for natural control of SLW populations. Following the initial outbreak in 2001/02, SLW abundance declined and stabilised over the next three seasons. The population dynamics of SLW is characterised by inter-seasonal population cycling between the non-crop (weed) and cotton components of the EIA cropping system. Cotton was the largest sink for and source of SLW during the study period. Over-wintering populations dispersed from weed host plant sources to cotton in spring followed by a reverse dispersal in late summer and autumn to broad-leaved crops and weeds. A basic spatial source-sink analysis showed that SLW adult and nymph densities were higher in cotton fields that were closer to over-wintering weed sources throughout spring than in fields that were further away. Cucurbit fields were not significant sources of SLW and did not appear to contribute significantly to the regional population dynamics of the pest. Substantial parasitism of nymphal stages throughout the study period indicates that native parasitoid species and other natural enemies are important sources of SLW mortality in Australian cotton production systems. Weather conditions and use of broad-spectrum insecticides for pest control are implicated in the initial outbreak and on-going pest status of SLW in the region.

Refined Global Analysis of Bemisia tabaci (Hemiptera: Sternorrhyncha: Aleyrodoidea: Aleyrodidae) Mitochondrial Cytochrome Oxidase 1 to Identify Species Level Genetic Boundaries.

Identifying species boundaries within morphologically indistinguishable cryptic species complexes is often contentious. For the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Sternorrhyncha: Aleyrodoidea: Aleyrodidae), the lack of a clear understanding about the genetic limits of the numerous genetic groups and biotypes so far identified has resulted in a lack of consistency in the application of the terms, the approaches use to apply them and in our understanding of what genetic structure within B. tabaci means. Our response has been to use mitochondrial gene cytochrome oxidase one to consider how to clearly and consistently define genetic separation. Using Bayesian phylogenetic analysis and analysis of sequence pairwise divergence we found a considerably higher to number of genetic groups than had been previously determined with two breaks in the distribution, one at 11% and another at 3.5%. At >11% divergence, 11 distinct groups were resolved, whereas at >3.5% divergence 24 groups were identified. Consensus sequences for each of these groups were determined and were shown to be useful in the correct assignment of sequences of unknown origin. The 3.5% divergence bound is consistent with species level separations in other insect taxa and Suggests that B. tabaci is it cryptic species composed of at least 24 distinct species. We further show that the placement of Bemesia atriplex (Froggatt) within the B. tabaci in, group adds further weight to the argument for species level separation within B. tabaci. This new analysis, which constructs consensus sequences and uses these its a standard against which unknown sequences call be compared, provides for the first time it consistent means of identifying the genetic hounds of each species with it high degree of certainty.

Intrapopulation variation in an Australian population of the North American thrips, Bagnalliella yuccae (Thysanoptera: Phlaeothripidae), a new record from Australia.

The genus Bagnalliella Karny is an endemic North American genus of Phlaeothripidae with 7 species associated with the New World plant genus Yucca; 2 Old World species currently placed in the genus are probably not congeneric. The number of sensoria on antennal segments III and IV has been used to distinguish the Bagnalliella species on Yucca, but an invasive population of Bagnalliella yuccae (Hinds) is reported here from Australia, at Brisbane, Queensland, in which the number of sensoria varied between individuals and even between left and right antennae of single individuals. These observations cast considerable doubt on the validity of some of the North American species of Bagnalliella. The Australian population was damaging young leaves of Yucca elephantipes, and indicates the ease with which thrips can be distributed by the horticultural trade.

Best management options for onion thrips in onions

Best management options for onion thrips.

Descriptions and keys to fungus-feeding Australian species in 5 genera of thrips

Fifty species in five genera of fungus feeding thrips, collected in part by Bush Blitz, are described. Details of 35 new species are combined with species previously named but not recognisable from literature, and illustrated identification keys to all species published. All specimens are data-based. These thrips are important ecologically, being associated with nutrient recycling from dead plants, and as food for various birds, lizards and frogs.

Australian spore-feeding thrips of the genus Phaulothrips (Thysanoptera, Idolothripinae)

Breeding by several of the spore-feeding species in the genus Phaulothrips is shown to be associated with abandoned tunnels of bees and scolytid beetles, as well as with the dead seed capsules of Eucalyptus species. The breeding sites for other species in the genus remain unknown, but 16 species are here recognised from Australia, of which the following six are newly described: P. daguilaris, P. flindersi, P. kingae, P. kranzae, P. oakeyi, P. whyallae. Copyright © 2013 Magnolia Press.

Diversity and abundance of fungivorous thrips (Thysanoptera) associated with leaf-litter and bark across forest types and two tree genera in subtropical Australia

Leaf-litter thrips were much more common and diverse in dry sclerophyll forest than in wetter forest types in subtropical southeast Queensland, Australia. In dry sclerophyll forest, the species composition of thrips in leaf-litter was strongly differentiated from the thrips fauna associated with bark of the trees Eucalyptus major and Acacia melanoxylon (4 of 34 species in common). The species composition of bark-dwelling thrips was similar across the two tree species and also across two eucalypts with different bark types, Eucalyptus major (flaky) and Eucalyptus siderophloia (rough). The diversity of thrips from the leaf-litter was not differentiated across all of these tree species. Virtually all thrips collected were Phlaeothripidae, subfamilies Idolothripinae and Phlaeothripinae. Idolothripinae were associated almost exclusively with leaf-litter, but Phlaeothripinae were in leaf-litter and bark. The association of fungal-feeding thrips with dry sclerophyll forest raises questions about their ecological requirements and the role they play in nutrient cycling. © 2012 Copyright Taylor and Francis Group, LLC.

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 (5.31.2, 8.52.9, 20.59.1 and 28.25.6%) 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.