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Westerlo, Belgium

Meeus I.,Ghent University | Mosallanejad H.,Ghent University | Niu J.,Ghent University | de Graaf D.C.,Ghent University | And 2 more authors.
Journal of Invertebrate Pathology | Year: 2014

Honeybees and bumblebees are the most important pollinators of agricultural crops. For this purpose honeybees and bumblebees are reared and transported. A pathogen-free status of bees in general, is crucial. Indeed anthropogenic transports of hosts carrying parasites could alter the natural host/pathogen association, inducing an extra pathogenic stress. Therefore the creation of a pathogen-free rearing environment is needed. For bumblebees this is possible, as these species are reared in a closed environment. Although, a link remains between reared bumblebees and the outside bee community, as honeybee-collected pollen is essential food for bumblebee mass rearing. Here we evaluated if gamma irradiation can minimize the risk of this potential route of exposure and can inactivate viral particles present in honeybee-collected pollen. We show that 16.9. kGy gamma irradiation induced a 100-1000 fold reduction on the ability of IAPV to cause mortality after injections. This result opens avenues toward rearing pathogen-free bumblebees and towards eliminating the risks of pathogen spillover to native wild bee species. © 2014 Elsevier Inc. Source


Meeus I.,Ghent University | de Miranda J.R.,Swedish University of Agricultural Sciences | de Graaf D.C.,Ghent University | Wackers F.,Biobest | Smagghe G.,Ghent University
Journal of Invertebrate Pathology | Year: 2014

Israeli acute paralysis virus (IAPV) together with Acute bee paralysis virus (ABPV) and Kashmir bee virus (KBV) constitute a complex of closely related dicistroviruses. They are infamous for their high mortality after injection in honeybees. These viruses have also been reported in non-Apis hymenopteran pollinators such as bumblebees, which got infected with IAPV when placed in the same greenhouse with IAPV infected honeybee hives. Here we orally infected Bombus terrestris workers with different doses of either IAPV or KBV viral particles. The success of the infection was established by analysis of the bumblebees after the impact studies: 50days after infection. Doses of 0.5×107 and 1×107 virus particles per bee were infectious over this period, for IAPV and KBV respectively, while a dose of 0.5×106 IAPV particles per bee was not infectious. The impact of virus infection was studied in micro-colonies consisting of 5 bumblebees, one of which becomes a pseudo-queen which proceeds to lay unfertilized (drone) eggs. The impact parameters studied were: the establishment of a laying pseudo-queen, the timing of egg-laying, the number of drones produced, the weight of these drones and worker mortality. In this setup KBV infection resulted in a significant slower colony startup and offspring production, while only the latter can be reported for IAPV. Neither virus increased worker mortality, at the oral doses used. We recommend further studies on how these viruses transmit between different pollinator species. It is also vital to understand how viral prevalence can affect wild bee populations because disturbance of the natural host-virus association may deteriorate the already critically endangered status of many bumblebee species. © 2014 Elsevier Inc. Source


Tena A.,Instituto Valenciano Of Investigaciones Agrarias Ivia | Pekas A.,Biobest | Pekas A.,Polytechnic University of Valencia | Wackers F.L.,Biobest | And 2 more authors.
Ecological Entomology | Year: 2013

Adult parasitoids depend on sugar-rich foods such as nectar and honeydew to meet their energy requirements and control insect pests. However, it is poorly known whether parasitoids can detect and feed on honeydew in agroecosystems, where it is the primary carbohydrate source, because this sugar source is less apparent in comparison to nectar and sometimes contains repellent compounds for parasitoids. High-performance liquid chromatography (HPLC) analyses were carried out to test whether Aphytis melinus DeBach (Hymenoptera: Aphelinidae), a parasitoid whose host does not produce honeydew, feeds on honeydew from non-hosts. In addition, the correlation between the parasitoid's sugar reserves and honeydew abundance was determined. To do this, both the levels of honeydew producers and the sugar levels of individual collected parasitoids were assessed during different seasons. The overall sugar content was treated as an indicator of energy reserves and the erlose-melezitose ratio as an indicator of honeydew feeding. The data show that A. melinus fed commonly on honeydew from non-host hemipterans. More than 50% of the female parasitoids collected in spring and summer had recently fed on honeydew and most of them showed a high sugar content. However, in autumn, when the number of honeydew producers was three times lower than in spring and summer, less than 20% of A. melinus were found to have fed on honeydew, with the average total sugar content being reduced by a factor of three. This study demonstrates that A. melinus commonly feeds on honeydew in the field, even though its host does not produce honeydew. The results also suggest that the exploitation of honeydew by A. melinus is a function of the density and species of honeydew producers. © 2013 The Royal Entomological Society. Source


Tena A.,Instituto Valenciano Of Investigaciones Agrarias Ivia | Pekas A.,Biobest | Pekas A.,University of Valencia | Cano D.,Instituto Valenciano Of Investigaciones Agrarias Ivia | And 3 more authors.
Journal of Applied Ecology | Year: 2015

There is increasing interest in the use of food supplements in agriculture to enhance the performance of parasitoids as part of conservation biological control. Nevertheless, there is limited evidence demonstrating the effectiveness of this approach, and this shortage of successful examples raises doubt regarding the validity of this approach. The use of sugar sources relies on tiered premises that: (i) parasitoids are sugar limited and (ii) this limitation is alleviated through the provision of sugar sources, thereby increasing both (iii) parasitoid fitness and (iv) the population density, which together lead to (v) an increase in parasitism. In the present study, we address these five premises through experiments examining the release of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) into the citrus agroecosystem with and without sugars. The results demonstrated that A. melinus is sugar limited when honeydew producers are scarce in the field. The provision of sugars did not increase the sugar contents in A. melinus females but rather increased the realized fecundity in these parasitoids, suggesting that females use energy for foraging and oviposition. Sugar sources increased the parasitoid population density twofold, and this increase most likely reflects the enhanced parasitoid longevity. Higher population densities and the increased realized fecundity of A. melinus obtained from trees with sugars were reflected in a twofold increase of parasitized hosts. Synthesis and applications. This study provides the first evidence supporting the five premises underlying sugar provisioning for parasitoids and demonstrates the potential value of sugar provisioning to enhance natural pest control in agricultural systems. This study provides the first evidence supporting the five premises underlying sugar provisioning for parasitoids and demonstrates the potential value of sugar provisioning to enhance natural pest control in agricultural systems. © 2015 British Ecological Society. Source


Tena A.,Instituto Valenciano Of Investigaciones | Wackers F.L.,Biobest | Wackers F.L.,Lancaster University | Heimpel G.E.,University of Minnesota | And 3 more authors.
Current Opinion in Insect Science | Year: 2016

One focus of conservation biological control studies has been to improve the nutritional state and fitness of parasitoids by adding nectar and artificial sugars to agroecosystems. This approach has largely overlooked the presence of honeydew, which is likely the primary carbohydrate source available to parasitoids in many agroecosystems. Over the last decade, it has been demonstrated that parasitoids often utilize this sugar source and there is evidence that honeydew can indirectly impact the population dynamics of herbivores through its nutritional value for parasitoids. The consumption of honeydew by parasitoids can shape direct and indirect interactions with other arthropods. The strength of these effects will depend on: first, parasitoid biology, second, the presence of other sugar sources (mainly nectar), third, the quality and quantity of the honeydew, and fourth, the presence and competitive strength of other honeydew consumers such as ants. The combination of these four factors is expected to result in distinct scenarios that should be analyzed for each agroecosystem. This analysis can reveal opportunities to increase the biocontrol services provided by parasitoids. Moreover, honeydew can be a resource-rich habitat for insect pathogens; or contain plant secondary chemicals sequestered by hemipterans or systemic insecticides toxic for the parasitoid. Their presence and effect on parasitoid fitness will need to be addressed in future research. © 2016 Elsevier Inc. All rights reserved. Source

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