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Vandekerkhove B.,Laboratory of Agrozoology | De Clercq P.,Laboratory of Agrozoology
Biological Control | Year: 2010

For the mass production of the mirid predator Macrolophus pygmaeus eggs of the Mediterranean flour moth Ephestia kuehniella are routinely used as an effective but expensive factitious food. In the current study, the potential of pollen as a supplementary food for M. pygmaeus was investigated. In a first experiment, the minimum amount of E. kuehniella eggs needed for optimal development and reproduction was determined to be 40 eggs per individual per 3 days. Then, different amounts of E. kuehniella eggs were offered to individual nymphs, supplemented or not with frozen moist honeybee pollen. Insects reared on only 10 E. kuehniella eggs per 3 days suffered higher mortality, developed slower and had lower adult weights and oocyte counts than insects reared on 40 E. kuehniella eggs or 10 eggs supplemented with pollen. When the nymphs were fed only pollen, survival rates and oocyte production were lower than when both pollen and flour moth eggs were provided. On pollen alone, ca. 80% of the nymphs successfully reached adulthood; their adult weights and oocyte counts were, respectively, 12% and 32% lower compared with individuals fed optimal amounts of flour moth eggs. When an egg yolk-based artificial diet was supplemented with bee pollen, development and fecundity were better than on the artificial diet alone. The practical implications of pollinivory for the mass production and the use of this beneficial insect in augmentative biological control programs are discussed. © 2010 Elsevier Inc. All rights reserved.

Berkvens N.,Laboratory of Agrozoology | Bale J.S.,University of Birmingham | Berkvens D.,Institute of Tropical Medicine | Berkvens D.,Ghent University | And 2 more authors.
Journal of Insect Physiology | Year: 2010

As an essential aspect of its invasive character in Europe, this study examined the cold hardiness of the harlequin ladybird Harmonia axyridis. This was done for field-collected populations in Belgium overwintering either in an unheated indoor or an outdoor hibernaculum. The supercooling point, lower lethal temperature and lower lethal time at 0 and -5 °C were determined. Possible seasonal changes were taken into account by monitoring the populations during each winter month. The supercooling point and lower lethal temperature remained relatively constant for the overwintering populations in the outdoor hibernaculum, ranging from -17.5 to -16.5 °C and -17.1 to -16.3 °C, respectively. In contrast, the supercooling point and lower lethal temperature of the population overwintering indoors clearly increased as the winter progressed, from -18.5 to -13.2 °C and -16.7 to -14.1 °C, respectively. A proportion of the individuals overwintering indoors could thus encounter problems surviving the winter due to premature activation at times when food is not available. The lower lethal time of field populations at 0 and -5 °C varied from 18 to 24 weeks and from 12 to 22 weeks, respectively. Morph type and sex had no influence on the cold hardiness of the overwintering adults. In addition, all cold tolerance parameters differed greatly between the laboratory population and field populations, implying that cold tolerance research based solely on laboratory populations may not be representative of field situations. We conclude from this study that the strong cold hardiness of H. axyridis in Europe may enable the species to establish in large parts of the continent. © 2009 Elsevier Ltd. All rights reserved.

Berkvens N.,Laboratory of Agrozoology | Moens J.,Laboratory of Agrozoology | Berkvens D.,Institute of Tropical Medicine | Samih M.A.,P.A. College | And 2 more authors.
Biological Control | Year: 2010

The enemy release hypothesis states that the absence of effective natural enemies can be a fundamental aspect leading to the successful establishment of an invasive species. This study investigates the impact of the native braconid parasitoid Dinocampus coccinellae on European populations of the invasive ladybird Harmonia axyridis. The parasitoid attacked adults and fourth instars of the ladybird more frequently than pupae and third instars. When given a choice, D. coccinellae attacked non-melanic adults and adults of a long term laboratory population of H. axyridis more often than melanic adults and adults of a field population, respectively. However, in no choice tests the parasitoid attacked individuals of either morph type and of the field and laboratory populations with the same frequency. Immature development of D. coccinellae took longer at lower temperatures and when less advanced developmental host stages (larvae and pupae) were successfully parasitized. The parasitoid emergence rates ranged from 0% to 14.7% on field populations of H. axyridis depending on life stage of the host attacked and up to 16.9% when adults of a long term laboratory population were attacked. Successfully parasitized ladybirds showed reduced reproductive capacities (6-12% of unparasitized individuals) and aphid consumption rates (85% of unparasitized individuals), but these effects together with the low emergence rates of the parasitoid suggest that D. coccinellae may only have a marginal impact on the population growth of H. axyridis in Europe. © 2009 Elsevier Inc. All rights reserved.

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