Knowledge about the foraging behaviour of parasitoids is essential to estimate the efficiency of biological control agents and to develop parasitoid release strategies. In this paper the behaviour of A fuscipennis when searching for TYialeurodes vaporariomm nymphs on bean plants was studied under laboratory conditions. The residence time and searching behaviour of A. fuscipennis were determined on plants sprayed or unsprayed with a sulphur-based fungicide, and infested or uninfested with nymphs of T. vaporariorum. The residence time and walking activity of A. fuscipennis on infested, unsprayed plants were higher than that of uninfested or sprayed plants. The residence time of A. fuscipennis was prolonged by both, encounters with unparasitized hosts and by feeding from the plant. Results suqqest that: 1) residence time was reduced on fungicide sprayed plants, indicating that the fungicide disturbed A fuscipennis, when A. fuscipennis is used within an Integrated Pest Managment (IPM) system for A. fuscipennis, special care must be taken on that the release and migration of the parasite to the crop does not happen immediately after a sulfurated fungicide has been applied. 2) Despite being a pro-ovigenic parasitoid that emerges with their life-time egg load ready to oviposit, A. fuscipennis needs to feed on the plant probably because searching for hosts demands extra energy.