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Augmentative biological control is a pest management strategy relying on the release of large numbers of natural enemies. It has been proved to be a successful alternative for chemical control especially in some areas of agriculture such as greenhouses. Providing high quality mass-reared natural enemies is essential for their use to combat pests. In this thesis, I focused on the study of diets for Orius majusculus, a predator commonly used in Europe for thrips control. As with many other heteropteran predators, the production of O. majusculus relies on the use of the eggs of the Mediterranean flower moth Ephestia kuehniella as a rearing diet. One of the main drawbacks is the high price of the eggs, ultimately increasing the price to pay for the growers. The use of artificial diets would reduce the complexity of the system by eliminating the need to rear a second species (i.e. the E. kuehniella moths). For this reason, six artificial diets varying in their macronutrient composition were tested as alternatives to E. kuehniella eggs. Results showed that nymphal survival and developmental time were acceptable in most artificial diets but female body weight and oviposition were reduced when compared to a diet of E. kuehniella eggs, which would prevent the artificial diets to be used commercially. When it comes to the different composition of the diets, offering the diets in ad libitum quantities and the lack of some essential nutrients potentially prevented bigger differences to appear between artificial diets. Finding alternative factitious prey to E. kuehniella eggs that are cheaper and simpler to produce could be a faster way to find alternative diets that reduce the production costs of O. majusculus. For this purpose, a study testing the use of frozen adults of Drosophila melanogaster of two different body compositions (a lipid rich and a protein rich) as alternative rearing diets was carried out. In the study, both the possibility of using D. melanogaster flies as n

Faba bean, Vicia faba, is becoming an increasingly popular crop with Danish farmers, and will become increasingly important in the future due to its nitrogen fixation properties and high protein content. The black bean aphid, Aphis fabae, is one of the most important pests of faba bean. Since pesticides are not a sustainable solution for control of A. fabae, it is important to investigate other control strategies. One potential strategy that could prove important in the future of faba bean production is biological control, in which natural enemies are used to suppress pest populations in the field. The parasitoid wasp Aphidius ervi and the ladybird Adalia bipunctata was tested alone and in combination for this purpose under confined no-choice conditions. Non-consumptive mortality effects occurring after the removal of the natural enemies, was included as a measure of aphid mortality. The results indicate that A. bipunctata shows the greatest potential to control A. fabae, but that A. ervi also has a significant effect on aphid mortality, especially when non-consumptive effects are included. Interspecific interference was only observed in relation to non-consumptive effects, where a significant difference in aphid mortality was found between A. ervi and the treatment containing the combination of the two species. However, combining the two species does not appear to achieve an additive effect. In itself, non-consumptive effects did not have a significant effect on aphid mortality in any treatments, but did affect the end results when combined with the aphid mortality caused directly by predation or parasitation. This indicates that future studies on biological control agents should record mortality for an extended period after the removal of the control agent, to get a more full picture of the effect on prey mortality. The results also show that A. fabae serves as a host of high quality to the immature stage of A. ervi, and that it might have a potential in

Production of tomato in Tanzania is the largest among the vegetables. However, smallholders are still facing high production losses due to insect pests. Traditionally, while the problem of pest has been dealt with through the use of pesticides, their frequent overuse has lead to environmental and health problems. A potential alternative to the use of pesticides could be mulching, an inexpensive method consisting in the application of an organic layer around the plants. The present study investigated the potential of mulch to contribute to conservation biological control of aphids and Helicoverpa armigera (Hübner) in organic tomato. We used 3x3m2 plots to compare three treatments (1) pine mulch consisting of pine needles applied to 15cm thickness and constantly replenished, (2) grass mulch consisting of wild lemongrass applied to 15 cm thickness and constantly replenished and (3) control consisting of hand-weeded bare soil. Abundance of the soil-arthropod community, including ground-dwelling predators, was assessed with pitfall trapping throughout the season. Aphid numbers were visually counted and predation on H. armigera was measured using sentinel Ephestia kuehniella (Zeller) eggs. Furthermore, capacity tests of selected predators were carried out in the laboratory. Overall, the presence of mulch increased the abundance of generalist predators over the growing season and the numbers of spiders, Carabidae and Staphylinidae became higher in grass mulch than in control plots. Collembolans were also affected by treatment, but no differences were found for the Formicidae and Gryllidae. Regarding pests, the aphid Macrosiphum euphorbiae (Thomas), the main aphid species attacking tomato, was generally found in lower numbers at mulch plots. This study suggests that enhanced numbers of ground-dwelling predators in mulch plots could be the main cause for lower number of aphids. Predation of sentinel prey did not quite match the numbers of predators at pitfalls suggesting