Drosophila use substrate odours and pheromones to localize oviposition places. D. busckii oviposits normally on rotten plant substrates, in which bacteria and yeasts grow. Drosophila species can be a vector for these bacteria and yeasts and infect new substrates with these microorganisms (Fogleman and Foster, 1988). Boers (1997) showed that D. busckii can be a vector of the bacteria Erwinia carotovora subsp. carotovora (here referred to as Ecc). Ecc induces softrot in for example chicory. Drosophila busckii is therefore considered a pest species in commercial chicory growth, and growers use permethrin against it. A good monitoring system is necessary to avoid pointless spraying of the pesticide. For the development of a monitoring trap, the selection of an attractive substrate is needed. Our experiments showed that the flies were significantly more attracted to thawed chicory than to thawed cauliflower. With the addition of pheromones and Ecc, the substrate became even more attractive. There is a minimum amount of pheromone and time for the bacteria needed to make the substrate attractive. The tested substrates were significantly more attractive to female than to male flies.