PCS Ornamental Plant Research

Destelbergen, Belgium

PCS Ornamental Plant Research

Destelbergen, Belgium
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Moerkens R.,University of Antwerp | Leirs H.,University of Antwerp | Leirs H.,University of Aarhus | Peusens G.,Pcfruit | And 3 more authors.
Journal of Applied Entomology | Year: 2012

Beneficial arthropods are often used for suppressing specific pest outbreaks in agricultural crop systems. The European earwig, Forficula auricularia L., (Dermaptera: Forficulidae), is an important natural enemy in fruit orchards. Recently, ecological studies were published describing earwig dispersal and survival during summer, hereby revealing clear differences between populations with a single brood (SBP) and two broods a year (DBP). In this article, we will describe three potential mortality factors of earwigs during the underground winter period, namely cold temperatures, parasitoids and soil tillage. This knowledge is essential for making efficient management strategies for increasing earwig abundance in fruit orchards. The effect of cold temperatures was checked during a 3-year semi-field experiment. Parasitism rates of Triarthria spp. (Fallén) and Ocytata pallipes (Fallén) (Diptera: Tachinidae) were obtained in a rearing experiment. The negative effect of soil tillage on the survival of earwigs nests was checked in a field experiment covering a 4-year time period. A strong, negative relation between temperature [cooling day degrees (CDD)] and survival of female and male earwigs during winter was found. Male earwigs of SBP died very quickly, mimicking natural conditions. Between 60% and 90% of females do not survive winter. Survival of females in DBP was higher than in SBP. Parasitism rates vary a lot between species, generation, year and location (0-20%). During winter, we found a maximum mortality of 13%. There is a clear trend that soil tillage can reduce the number of nymphs in spring and summer by 50%. Implications for biocontrol are the following: (i) mortality owing to temperature can be predicted using CDD and if necessary preventive management actions can be undertaken to control pests; (ii) parasitism rates are negligible compared to high impact of temperature; and (iii) soil tillage can be timed more accurately using a recently developed day degree model. © 2011 Blackwell Verlag, GmbH.

Parkinson J.F.,University of Sussex | Gobin B.,PCS Ornamental Plant Research | Hughes W.O.H.,University of Sussex
Physiological Entomology | Year: 2017

Symbiotic bacteria are highly diverse, play an important role in ecology and evolution, and are also of applied relevance because many pest insects rely on them for their success. However, the dynamics and regulation of symbiotic bacteria within hosts is complex and still poorly understood outside of a few model systems. One of the most intriguing symbiotic relationships is the obligate, tripartite nutritional mutualism in sap-feeding, economically-destructive mealybugs (Hemiptera: Sternorrhyncha: Pseudococcidae), which involves γ-proteobacteria hosted within β-proteobacteria hosted within the mealybugs. The present study examines whether there is population variation in symbiont density (i.e. infection intensity, or titre) in the citrus mealybug Planococcus citri (Risso) and how this impacts host life-history. Symbiont density is found to differ significantly between populations when reared under controlled environmental conditions, indicating that the density of symbiont infections is influenced by host or symbiont genotype. However, symbiont density changes in populations over multiple generations, indicating that symbiont densities are dynamic. Surprisingly, given that the symbionts are essential nutritional mutualists, the density of the symbionts does not correlate significantly with either host fecundity or development. Higher levels of symbionts have no clear benefit to hosts and therefore appear to be superfluous, at least under constant, optimized environmental conditions. Excessive symbiont density may be an evolutionary artefact from a period of inefficient vertical transmission when the balance of conflict between host and symbiont was still being established. © 2017 The Royal Entomological Society

PubMed | PCS Ornamental Plant Research, Vietnam National University, Hanoi and Ghent University
Type: Journal Article | Journal: PloS one | Year: 2015

The impact of daily temperature variations on arthropod life history remains woefully understudied compared to the large body of research that has been carried out on the effects of constant temperatures. However, diurnal varying temperature regimes more commonly represent the environment in which most organisms thrive. Such varying temperature regimes have been demonstrated to substantially affect development and reproduction of ectothermic organisms, generally in accordance with Jensens inequality. In the present study we evaluated the impact of temperature alternations at 4 amplitudes (DTR0, +5, +10 and +15C) on the developmental rate of the predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) and their natural prey, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). We have modelled their developmental rates as a function of temperature using both linear and nonlinear models. Diurnally alternating temperatures resulted in a faster development in the lower temperature range as compared to their corresponding mean constant temperatures, whereas the opposite was observed in the higher temperature range. Our results indicate that Jensens inequality does not suffice to fully explain the differences in developmental rates at constant and alternating temperatures, suggesting additional physiological responses play a role. It is concluded that diurnal temperature range should not be ignored and should be incorporated in predictive models on the phenology of arthropod pests and their natural enemies and their performance in biological control programmes.

Vangansbeke D.,Ghent University | de Schrijver L.,Ghent University | Spranghers T.,Ghent University | Audenaert J.,PCS Ornamental Plant Research | And 6 more authors.
Experimental and Applied Acarology | Year: 2013

Increasing energy costs force glasshouse growers to switch to energy saving strategies. In the temperature integration approach, considerable daily temperature variations are allowed, which not only have an important influence on plant growth but also on the development rate of arthropods in the crop. Therefore, we examined the influence of two constant temperature regimes (15 °C/15 °C and 20 °C/20 °C) and one alternating temperature regime (20 °C/5 °C, with an average of 15 °C) on life table parameters of Phytoseiulus persimilis and Neoseiulus californicus and their target pest, the two-spotted spider mite Tetranychus urticae at a 16:8 (L:D) h photoperiod and 65 ± 5 % RH. For females of both predatory mites the alternating temperature regime resulted in a 25-30 % shorter developmental time as compared to the corresponding mean constant temperature regime of 15 °C/15 °C. The immature development of female spider mites was prolonged for 7 days at 15 °C/15 °C as compared to 20 °C/5 °C. With a daytime temperature of 20 °C, no differences in lifetime fecundity were observed between a nighttime temperature of 20 and 5 °C for P. persimilis and T. urticae. The two latter species did show a higher lifetime fecundity at 20 °C/5 °C than at 15 °C/15 °C, and their daily fecundity at the alternating regime was about 30 % higher than at the corresponding mean constant temperature. P. persimilis and T. urticae showed no differences in sex ratio between the three temperature regimes, whereas the proportion of N. californicus females at 15 °C/15 °C (54.2 %) was significantly lower than that at 20 °C/5 °C (69.4 %) and 20 °C/20 °C (67.2 %). Intrinsic rates of increase were higher at the alternating temperature than at the corresponding mean constant temperature for both pest and predators. Our results indicate that thermal responses of the studied phytoseiid predators to alternating temperature regimes used in energy saving strategies in glasshouse crops may have consequences for their efficacy in biological control programs. © 2013 Springer Science+Business Media Dordrecht.

Parkinson J.F.,University of Sussex | Gobin B.,PCS Ornamental Plant Research | Hughes W.O.H.,University of Sussex
Entomologia Experimentalis et Applicata | Year: 2014

Mealybugs are sap-feeding insect pests that pose a serious threat to horticulture. The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), like most other mealybug species, harbours two obligate maternally transmitted bacterial endosymbionts, which are essential for nutrient acquisition and host survival. These are 'Candidatus Tremblaya princeps', a member of the β-Proteobacteria, and 'Candidatus Moranella endobia', a member of the γ-Proteobacteria. The density of symbionts in the hosts is now understood to be dynamic, being influenced by the age and gender of the host and by environmental conditions during development. Here, we examine the impact of short-term heat stress treatment on the obligate symbionts and life-history parameters of P. citri, using qPCR to measure changes in symbiont density. Heat stress killed juveniles and adult males, and significantly reduced levels of 'Ca. Moranella endobia' and 'Ca. Tremblaya princeps' in adult females. However, adult females were resilient to this and it did not affect their fecundity or brood survival, although the sex ratio of their brood was slightly, but significantly, more female biased. Our results suggest that 'Ca. Tremblaya princeps' and 'Ca. Moranella endobia' are not as essential to the survival of adult mealybugs as they are to the survival of immature mealybugs and that sub-lethal heat treatment alone is unlikely to be effective as a disinfestation tactic. © 2014 The Netherlands Entomological Society.

Vangansbeke D.,Ghent University | Nguyen D.T.,Ghent University | Nguyen D.T.,Hanoi University of Agriculture | Audenaert J.,PCS Ornamental Plant Research | And 4 more authors.
BioControl | Year: 2014

Amblydromalus limonicus Garman & McGregor (Acari: Phytoseiidae) is a generalist predatory mite with economic potential to control thrips and whiteflies in protected cultivation. We tested the development and reproduction of A. limonicus on three food sources with potential for use in laboratory production or to support its populations in a crop: fresh cattail pollen, Typha latifolia L. (Poales: Typhaceae), dry decapsulated cysts of the brine shrimp Artemia franciscana Kellogg (Branchiopoda: Artemiidae) and frozen eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The diets were tested both on an artificial substrate and on kidney bean leaves. In the absence of food, all larvae died on the artificial substrate, whereas they succeeded in reaching the protonymphal stage on bean leaves. Immature survival was high (>90 %) on all diet-substrate combinations, except when E. kuehniella eggs were offered on the artificial substrate (35 % survival). Both sexes showed the fastest development when offered E. kuehniella eggs on leaf discs, followed by A. franciscana cysts, whereas the slowest development was achieved on T. latifolia pollen. Fecundity and oviposition rate were higher on E. kuehniella and A. franciscana than on T. latifolia. Amblydromalus limonicus females lived longer on the leaf discs than on the artificial substrates. The intrinsic rate of increase (rm) was highest when E. kuehniella eggs were offered on leaf discs (0.256 females per female per day), whereas the lowest rate (0.128 females per female per day) was obtained when the eggs were provided on artificial substrates. The intrinsic rate of increase on A. franciscana cysts was not affected by substrate and averaged 0.22 females per female per day. Diet significantly influenced the size of A. limonicus females as measured by the distance between specific setae on the dorsal shield of the idiosoma. The application of the investigated food sources to sustain a colony of predatory mites upon their release in a greenhouse crop is discussed. © 2013 International Organization for Biological Control (IOBC).

Christiaens A.,PCS Ornamental Plant Research | Christiaens A.,Ghent University | Gobin B.,PCS Ornamental Plant Research | Van Labeke M.C.,Ghent University
Acta Horticulturae | Year: 2016

Efficient adventitious rooting is a key process in the vegetative propagation of horticultural and woody species. A well-rooted cutting is essential for optimal growth and high quality plants. The use of spectral light quality to influence adventitious rooting has been studied for many years, but got a lot more attention since LEDs came on the market for horticultural practices. Contrasting results of the effect of light quality on adventitious rooting are reviewed in this paper. Even though more fundamental research is needed to easily determine which light quality can be used for a specific species, the use of LEDs for adventitious rooting is promising. For in vitro plantlets implementation can be done easily, for in vivo cuttings, the use of LEDs seems also promising in a multi-layered system. The controlled environment will lead to a year-round high quality rooted cutting production.

Christiaens A.,Ghent University | Christiaens A.,PCS Ornamental Plant Research | Pauwels E.,PCS Ornamental Plant Research | Gobin B.,PCS Ornamental Plant Research | Van Labeke M.-C.,Ghent University
Plant Growth Regulation | Year: 2014

Flowering is a complex process which starts with the induction and development of the flower buds. For azalea (Rhododendron simsii hybrids), flower induction was hastened by the application of chlormequat and took place within 11 days after treatment. Subsequent flower bud differentiation was not altered by the application rate of the plant growth regulators (PGR) chlormequat and paclobutrazol, nor by temperature or light sum. There were however, large genotypic variations in flower bud differentiation rate. For all cultivars a linear phase until flower primordia were fully differentiated and the style started to enlarge (flower bud stage 7), was followed by a slower final development (to stage 8). The linear phase was fastest for the semi-early-flowering cultivars (‘Mont Blanc’, ‘M. Marie’ and ‘Otto’), requiring only 46 or 48 days to reach flower bud stage 7 after the first PGR treatment. Two late-flowering cultivars (‘Thesla’ and ‘Sachsenstern’) had the slowest differentiation, requiring 64 days to reach stage 7. The early-flowering cultivars (‘H. Vogel’ sports) and two late-flowering cultivars (‘Mw. G. Kint’ and ‘Tamira’) required 54 and 52 days, respectively, after the first PGR treatment to reach stage 7. To reach flower bud stage 8, a similar trend in velocity was seen, the semi-early-flowering cultivars requiring the least amount of days (17–18 days), the late-flowering cultivars ‘Thesla’ and ‘Sachsenstern’ requiring the highest amount of days (24 days) and the early-flowering cultivars and the late-flowering cultivars ‘Mw. G. Kint’ and ‘Tamira’ requiring an intermediate number of days (20–22 days). © 2014, Springer Science+Business Media Dordrecht.

PubMed | PCS Ornamental Plant Research and Ghent University
Type: Journal Article | Journal: Pest management science | Year: 2016

In integrated pest management systems in greenhouse crops, the predatory mite Amblyseius swirskii is becoming increasingly important as a biological control agent of various pests, especially thrips and whiteflies. An emerging strategy to promote the predators establishment and retention in the crop consists in providing food supplements. However, when faced with omnivorous pests, such as the western flower thrips, Frankliniella occidentalis, food supplements need to be applied with extreme care, in order not to boost population growth of the pest. This laboratory study was conducted to evaluate the impact of commercial products of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia sp.) on populations of both pest and predator and on predator-prey interactions.Pollen was highly supportive for both F. occidentalis and A. swirskii, whereas Artemia cysts supported thrips populations to a lesser extent than those of the predator. Furthermore, a less pronounced reduction in thrips consumption by A. swirskii was observed in the presence of Artemia cysts as compared with T. angustifolia pollen.Artemia might be a valuable alternative to pollen for supporting populations of A. swirskii in order to improve thrips management, as they are less beneficial for the pest but do support population growth of A. swirskii.

Gobin B.,PCS Ornamental Plant Research | Audenaert J.,PCS Ornamental Plant Research | Vissers M.,PCS Ornamental Plant Research | Van Delsen B.,PCS Ornamental Plant Research | And 2 more authors.
Acta Horticulturae | Year: 2013

Outbreaks of the broad mite Polyphagotarsonemus latus cause serious economic damage in ornamental horticulture. Control of broad mites proves to be a serious challenge for growers. Good control throughout the crop cycle requires optimization and integration of chemical and non-chemical strategies. In this paper we describe results of trials testing the efficacy and applicability of 3 complementary control strategies: chemical, biological and physical. Field trials on two sensitive woody ornamental plants: Hedera and Azalea (Rhododendron simsii cultivars) show the value of these strategies. We test the strength of these independent strategies and suggest how these could be alternated to control broad mites throughout the production cycle. © ISHS 2013.

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