OVIPOSITION DETERRING PHEROMONE IN RHAGOLETIS-CERASI L - BIOLOGICAL-ACTIVITY OF 4 SYNTHETIC ISOMERS AND HMP DISCRIMINATION OF 2 HOST RACES AS MEASURED BY AN IMPROVED LABORATORY BIOASSAY

We describe an improved and more sensitive laboratory bioassay that allows a faster evaluation of the flies' reaction to HMP treated fruit. Based on earlier experiments and stimulated by a new test method developed for the apple maggot, Rhagoletis pomonella, we introduced as new methodological elements fresh host fruits and leaves as well as simultaneous direct observations of a small population of fruit fly females. The results of a first experimental series show a lower degree of HMP discrimination in the Lonicera host race as compared to the Prunus host race. These observed differences are apparently not related to a different sensitivity threshold at the level of the ODP specific tarsal receptors but probably caused by different behavioral patterns. In comparative tests carried out with the Prunus host race the biological activity of 2 of the 4 possible stereoisomers and of their naturally occuring mixture could be demonstrated. The advantages of the new test method are discussed.