Kann der Einsatz entomopathogener Nematoden zur nachhaltigen Bekämpfung der Kirschfruchtfliege beitragen?

The cherry fruit fly, Rhagoletis cerasi L., is the major pest of sweet cherries in Europe. Currently, no efficient control method is available and there is the risk of increasing population densities of this pest. Entomopathogenic nematodes caused high mortality of last instar maggots, when entering the soil for pupation, under laboratory and field conditions. First field applications of these biocontrol agents against pupating larvae in 2005 should test their efficacy to reduce pest densities. Accompanying field observations were made to evaluate the degree of natural mortality of the cherry fruit fly during the pupation phase in order to decide if the application of nematodes could substantially contribute to control this pest. According to the results in this year, natural mortality factors reduced the cherry fruit fly population from the period between larvae leaving the fruit until hatching of adults in the following year by 95%. The emergence rate of adult flies in spring 2006 was low (10 flies/qm) and no significant differences in the densities of emerging flies in untreated and treated areas were detected. Thus, the effect of applying nematodes remained unclear and additional methods are needed to define their impact separately from natural mortality.