Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Mite-mediated hyperphoretic dispersal of Ophiostoma spp. from the infructescences of South African Protea spp.
Roets, F. ; Crous, P.W. ; Wingfield, M.J. ; Dreyer, L.L. - \ 2009
Environmental Entomology 38 (2009)1. - ISSN 0046-225X - p. 143 - 152.
bark beetles - tarsonemus-mites - fungi - coleoptera - scolytidae - acarina
Ophiostomatoid fungi are well known as economically important pathogens and agents of timber degradation. A unique assemblage of these arthropod-associated organisms including species of Gondwanamyces G. J. Marais and M. J. Wingf., and Ophiostoma Syd. and P. Syd. occur in the floral heads (infructescences) of Protea L. species in South Africa. It has recently been discovered that Ophiostoma found in Protea flower-heads are vectored by mites (Acarina) including species of: Tarsonemus Canestrini and Fonzago, Proctolaelaps Berlese, and Trichouropoda Berlese. It is, however, not known how the mites carry the fungi between host plants. In this study, we consider two possible modes of mite dispersal. These include self-dispersal between infructescences and dispersal through insect vectors. Results showed that, as infructescences desiccate, mites self-disperse to fresh moist infructescences. Long-range dispersal is achieved through a phoretic association with three beetle species: Genuchus hottentottus (F.), Trichostetha fascicularis L., and T. capensis L. The long-range, hyperphoretic dispersal of O. splendens G. J. Marais and M. J. Wingf. and O. phasma Roets et al. seemed effective, because their hosts were colonized during the first flowering season 3-4 yr after fire.
Ophiostoma gemellus and Sporothrix variecibatus from mites infesting Protea infructescences in South Africa
Roets, F. ; Beer, Z.W. de; Wingfield, M.J. ; Crous, P.W. ; Dreyer, L.L. - \ 2008
Mycologia 100 (2008)3. - ISSN 0027-5514 - p. 496 - 510.
phoretic mites - bark beetles - sp-nov - phylogenetic inference - ceratocystis-minor - ips-typographus - fungi - scolytidae - coleoptera - complex
Ophiostoma (Ophiostomatales) represents a large genus of fungi mainly known from associations with bark beetles (Curculionidae: Scolytinae) infesting conifers in the northern hemisphere. Few southern hemisphere native species are known, and the five species that consistently occur in the infructescences of Protea spp. in South Africa are ecologically unusual. Little is known about the vectors of Ophiostoma spp. from Protea infructescences, however recent studies have considered the possible role of insects and mites in the distribution of these exceptional fungi. In this study we describe a new species of Ophiostoma and a new Sporothrix spp. with affinities to Ophiostoma, both initially isolated from mites associated with Protea spp. They are described as Ophiostoma gemellus sp. nov. and Sporothrix variecibatus sp. nov. based on their morphology and comparisons of DNA sequence data of the 28S ribosomal, ß-tubulin and internal transcribed spacer (ITS1, 5.8S, ITS2) regions. DNA sequences of S. variecibatus were identical to those of a Sporothrix isolate obtained from Eucalyptus leaf litter in the same area in which S. variecibatus occurs in Protea infructescences. Results of this study add evidence to the view that mites are the vectors of Ophiostoma spp. that colonize Protea infructescences. They also show that DNA sequence comparisons are likely to reveal additional cryptic species of Ophiostoma in this unusual niche.
Discovery of fungus-mite mutualism in a unique niche
Roets, F. ; Wingfield, M.J. ; Crous, P.W. ; Dreyer, L.L. - \ 2007
Environmental Entomology 36 (2007)5. - ISSN 0046-225X - p. 1226 - 1237.
protea infructescences - sp-nov - bark beetles - ophiostoma - gondwanamyces - symbiosis
The floral heads (infructescences) of South African Protea L. represent a most unusual niche for fungi of the economically important genus Ophiostoma Syd. and P. Syd. emend. Z.W. de Beer et al. Current consensus holds that most members of Ophiostoma are vectored by tree-infesting bark beetles. However, it has recently been suggested that mites, phoretic on these bark beetles, may play a central role in the dispersal of Ophiostoma. No bark beetles are known from Protea. Therefore, identifying the vectors of Ophiostoma in Protea infructescences would independently evaluate the role of various arthropods in the dispersal of Ophiostoma. Infructescence-colonizing arthropods were tested for the presence of Ophiostoma DNA using polymerase chain reaction (PCR) and for reproductive propagules by isolation on agar plates. PCR tests revealed that few insects carried Ophiostoma DNA. In contrast, various mites (Proctolaelaps vandenbergi Ryke, two species of Tarsonemus Canestrini and Fonzago, and one Trichouropoda Berlese species) frequently carried Ophiostoma propagules. DNA sequence comparisons for 28S ribosomal DNA confirmed the presence of O. splendens G. J. Marais and M. J. Wingf., O. palmiculminatum Roets et al., and O. phasma Roets et al. on these mites. Two apparently undescribed species of Ophiostoma were also identified. Light and scanning electron microscopy revealed specialized structures in Trichouropoda and one Tarsonemus sp. that frequently contained Ophiostoma spores. The Trichouropoda sp. was able to complete its life cycle on a diet consisting solely of its identified phoretic Ophiostoma spp. This study provides compelling evidence that mites are the primary vectors of infructescence-associated Ophiostoma spp. in South Africa.
Plant odours with potential for a push-pull strategy to control the onion thrips (Thrips tabaci)
Tol, R.W.H.M. van; James, D.E. ; Kogel, W.J. de; Teulon, D.A.J. - \ 2007
Entomologia Experimentalis et Applicata 122 (2007)1. - ISSN 0013-8703 - p. 69 - 76.
essential oils - bark beetles - pest-control - volatiles - protect
We compared the efficacy of four plant essential oils to repel onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae), in the presence of an attractive odour, ethyl iso-nicotinate in a pasture field. Four horizontal white sticky plates were placed adjacent to (directions: N, S, E, W) a central horizontal white plate (C). After 24 h, in the treatment combination where the four plates were sprayed with essential oil surrounding a central sticky plate sprayed with ethyl iso-nicotinate, fewer onion thrips were found on the plates treated with sweet marjoram [Origanum majorana L. (Labiatae)] or clove basil [Ocimum gratissimum L. (Labiatae)] (87 and 71% less, respectively) compared to the control treatment of four water-sprayed plates surrounding a central plate with ethyl iso-nicotinate. We also compared the distribution of onion thrips on the plates. Relative thrips numbers on each plate were compared with similar (N, S, E, W, and C) plates in the control treatment. There were relatively lower thrips numbers on the south (23% reduction) and west (26% reduction) O. majorana-treated plates and higher numbers (37% increase) on the central attractant-treated plate indicating a short-distance push-pull effect. When four plates were sprayed with the thrips attractant surrounding a central sticky plate sprayed with an essential oil or water (control), only O. majorana reduced the number of thrips on the attractant-sprayed plates (62% reduction). The distribution of thrips on the different plates within this treatment combination did not change substantially when compared to the distribution in the water-control treatment. Other essential oils tested (wormwood [Artemisia arborescens L. (Compositae)]) and tea tree [Melaleuca alternifolia (Maiden. & Betche.) Cheel. (Myrtaceae)]) were not effective in any of the treatments. It appears that O. majorana is a promising thrips repellent which could be used for further testing in a push-pull system with the attractant ethyl iso-nicotinate. The field setup used also proved to be a valuable tool for evaluating the potential of repellents to control onion thrips.
Direct and indirect chemical defence of pine against folivorous insects
Mumm, R. ; Hilker, M. - \ 2006
Trends in Plant Science 11 (2006)7. - ISSN 1360-1385 - p. 351 - 358.
dependent pheromone responses - spruce budworm defoliation - sawfly diprion-pini - scots pine - bark beetles - lodgepole pine - egg deposition - douglas-fir - natural defoliation - volatile emissions
The chemical defence of pine against herbivorous insects has been intensively studied with respect to its effects on the performance and behaviour of the herbivores as well as on the natural enemies of pine herbivores. The huge variety of terpenoid pine components play a major role in mediating numerous specific food web interactions. The constitutive terpenoid pattern can be adjusted to herbivore attack by changes induced by insect feeding or oviposition activity. Recent studies on folivorous pine sawflies have highlighted the role of induced pine responses in herbivore attack and have demonstrated the importance of analysing the variability of pine defence and its finely tuned specificity with respect to the herbivore attacker in a multitrophic context.
Multi-gene phylogeny for Ophiostoma spp. reveals two new species from Protea infructescences
Roets, F. ; Beer, Z.W. de; Dreyer, L.L. ; Zipfel, R. ; Crous, P.W. ; Wingfield, M.J. - \ 2006
Studies in Mycology 55 (2006). - ISSN 0166-0616 - p. 199 - 212.
mycangial fungi - bark beetles - south-africa - sp-nov - complex - scolytidae - coleoptera - symbiosis - survival - genus
Ophiostoma represents a genus of fungi that are mostly arthropod-dispersed and have a wide global distribution. The best known of these fungi are carried by scolytine bark beetles that infest trees, but an interesting guild of Ophiostoma spp. occurs in the infructescences of Protea spp. native to South Africa. Phylogenetic relationships between Ophiostoma spp. from Protea infructescences were studied using DNA sequence data from the P-tubulin, 5.8S ITS (including the flanking internal transcribed spacers 1 and 2) and the large subunit DNA regions. Two new species, O. phasma sp. nov. and O. paimiculminatum sp. nov. are described and compared with other Ophiostoma spp. occurring in the same niche. Results of this study have raised the number of Ophiostoma species from the infructescences of serotinous Protea spp. in South Africa to five. Molecular data also suggest that adaptation to the Protea infructescence niche by Ophiostoma spp. has occurred independently more than once.
Olfactory responses of banana weevil predators to volatiles from banana pseudostem tissue and synthetic pheromone
Tinzaara, W. ; Gold, C.S. ; Dicke, M. ; Huis, A. van - \ 2005
Journal of Chemical Ecology 31 (2005)7. - ISSN 0098-0331 - p. 1537 - 1553.
induced plant volatiles - infested pear trees - sordidus germar col - cosmopolites-sordidus - aggregation pheromone - parasitic wasps - pest-management - bark beetles - chemical communication - carnivorous arthropods
As a response to attack by herbivores, plants can emit a variety of volatile substances that attract natural enemies of these insect pests. Predators of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) such as Dactylosternum abdominale (Coleoptera: Hydrophilidae) and Pheidole megacephala (Hymenoptera: Formicidae), are normally found in association with weevil-infested rotten pseudostems and harvested stumps. We investigated whether these predators are attracted to such environments in response to volatiles produced by the host plant, by the weevil, or by the weevil¿plant complex. We evaluated predator responses towards volatiles from banana pseudostem tissue (synomones) and the synthetic banana weevil aggregation pheromone Cosmolure+ in a two-choice olfactometer. The beetle D. abdominale was attracted to fermenting banana pseudostem tissue and Cosmolure+, whereas the ant P. megacephala was attracted only to fermented pseudostem tissue. Both predators were attracted to banana pseudostem tissue that had been damaged by weevil larvae irrespective of weevil presence. Adding pheromone did not enhance predator response to volatiles from pseudostem tissue fed on by weevils. The numbers of both predators recovered with pseudostem traps in the field from banana mats with a pheromone trap were similar to those in pseudostem traps at different distance ranges from the pheromone. Our study shows that the generalist predators D. abdominale and P. megacephala use volatiles from fermented banana pseudostem tissue as the major chemical cue when searching for prey
The significance of background odour for an egg parasitoid to detect plants with host eggs
Mumm, R. ; Hilker, M. - \ 2005
Chemical Senses 30 (2005)4. - ISSN 0379-864X - p. 337 - 343.
achromatic cues - phytoseiulus-persimilis - olfactory responses - volatile emissions - insect herbivores - colored patterns - pinus-sylvestris - alarm pheromone - cotton plants - bark beetles
Scots pine has been shown to produce a volatile bouquet that attracts egg parasitoids in response to oviposition of the herbivorous sawfly Diprion pini. Previous analyses of headspace volatiles of oviposition-induced pine twigs revealed only quantitative changes; in particular, the sesquiterpene (E)-ß-farnesene was emitted in significantly higher quantities by oviposition-induced pine. Here we investigated whether (E)-ß-farnesene attracted the egg parasitoid Chrysonotomyia ruforum. We tested the behavioural response of C. ruforum females to different concentrations of (E)-ß-farnesene. Egg parasitoids did not respond to this sesquiterpene at either concentration tested. However, they did respond significantly to (E)-ß-farnesene when this compound was offered in combination with the volatile blend emitted from pine twigs without eggs. This response was dependent on the applied concentration of (E)-ß-farnesene. Further bioassays with other components [(E)-ß-caryophyllene, -cadinene] of the odour blend of pine were conducted in combination with the volatile blend from egg-free pine as background odour. None of the compounds tested against the background of odour from an egg-free pine twig were attractive to the egg parasitoid. These results suggest that the egg parasitoids responded specifically to (E)-ß-farnesene, but only when this compound was experienced in the `right` context, i.e. when contrasted with a background odour of non-oviposition-induced pine volatiles
Pheromone-mediated aggregation in nonsocial arthropods: an evolutionary ecological perspective
Wertheim, B. ; Baalen, E.J.A. van; Dicke, M. ; Vet, L.E.M. - \ 2005
Annual Review of Entomology 50 (2005). - ISSN 0066-4170 - p. 321 - 346.
tribolium-castaneum coleoptera - surinamensis l coleoptera - cis-vaccenyl acetate - onion maggot diptera - viridula l hemiptera - green stink bug - chemical ecology - bark beetles - drosophila-melanogaster - grain beetle
Although the use of aggregation pheromones has been reported for hundreds of nonsocial arthropod species, the evolutionary ecological aspects of this behavior have received little attention. Despite the elaborate literature on mechanisms, robust data on costs and benefits of aggregation pheromones are scant. Existing literature indicates that, in contrast to the diversity of mechanisms, the ecological conditions in which aggregation pheromones are used are more alike. This points to a few general categories for costs and benefits of aggregation pheromones, and these are discussed. We subsequently review interspecific interactions that may be affected by the use of aggregation pheromones. We encounter a strikingly frequent association of aggregation pheromones with fungi and microorganisms and address cross-attraction by competitor species and exploitation by natural enemies. We show that aggregative behavior by individuals through the use of pheromones can profoundly affect ecological interactions and advocate further evolutionary and ecological investigations of pheromone-mediated aggregation.
Effects of two pheromone trap densities against banana weevil Cosmopolites sordidus, populations and their impact on plant damage in Uganda
Tinzaara, W. ; Gold, C.S. ; Kagezi, G.H. ; Dicke, M. ; Huis, A. van; Nankinga, C. ; Tushemereirwe, W. ; Ragama, P.E. - \ 2005
Journal of Applied Entomology 129 (2005)5. - ISSN 0931-2048 - p. 265 - 271.
aggregation pheromone - field activity - bark beetles - coleoptera - curculionidae - volatiles - communication
An on-farm study to evaluate the effect of pheromone trap density on the population of the banana weevil, Cosmopolites sordidus (Germar) (Col., Curculionidae) was conducted in Masaka district, Uganda. The pheromone used was Cosmolure+, a commercially available weevil aggregation pheromone. Forty-two farms were assigned to one of three treatments: 0, 4 and 8 pheromone traps/ha. Pheromone lures were changed monthly at which time the traps were moved to a different location within the stand. Adult weevil population densities were estimated by using mark and recapture methodology at 0, 6, 12, 18 and 21 months, while damage to the banana corm was assessed at 0, 3, 6, 12, 18 and 21 months since the start of the experiment. Pheromone trap captures were generally low: about 10 weevils per trap per month. There were no significant differences in mean catches of C. sordidus per trap per month except for February 2002 when doubling the pheromone trap density decreased weevil catches. Although not significant, decreased efficiency was also the trend in higher trap densities over all the data sets. Doubling the number of traps increased the number of weevils caught per hectare per month from 0.4 to 0.6%. There was no significant difference in plant damage between the pheromone treatments in low- compared with high-trap densities. There were generally no significant differences in weevil populations and plant damage between pheromone-treated and control farms. Possible reasons for the low-trap efficacy in this study are discussed
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