In Belgian pear production growers may encounter major economic problems when fruit becomes damaged by bugs. One of the major pests belongs to the stink bugs, Pentatoma rufipes L. (Heteroptera, Pentatomidae) which feeds by piercing into buds, flowers and fruit. To study the population dynamics of this species it was monitored in organic pear orchards by the beating tray method. Results revealed their univoltine life cycle and their presence within the orchard during the entire year. They overwinter in the second nymphal stage and become active in March/April. After 3 moultings adulthood is reached during May/June. In summer mating takes place and eggs are laid at the underside of the leaves of the fruit trees. By the end of August the eggs hatch and the first young nymphs appear. At first they aggregate but when they have moulted into the next stage dispersal takes place (September) and by October they search for hiding places on the trees to hibernate. As damage is done before and after blossom the application of an insecticide has to be well defined and timed. Therefore the efficacy of spinosad and natural pyrethrum, applied once or twice before and/or after bloom, was compared in a field trial. Data indicated that a single application of spinosad after bloom and a double application of spinosad or pyrethrum (before and after bloom) reduced the number of bugs with 83.3%. Damage to the crop was the lowest (4.5%) when spinosad was applied twice but no statistical difference with both other applications was found.