Field applications of entomopathogenic fungi against Rhagoletis cerasi

Two myco-insecticides, Naturalis-L (Beauveria bassiana) and PreFeRal®WG (Paecilomyces fumosoroseus), were applied against adult R. cerasi (Diptera: Tephritidae) in two orchards in north-western Switzerland in summer 2006. Both products were applied at a concentration of 5.75x104 CFU / ml. With four applications at seven day intervals the whole flight period of R. cerasi was fully covered. During this period (5th June - 6th July) the temperature averaged 19.2°C, total precipitation was 60 mm. Under these conditions Naturalis-L significantly reduced the number of damaged fruit (efficacy: 69-74%), whereas damage was not significantly reduced with PreFeRal®WG (efficacy: 27%). Fungus infested flies were found on the yellow sticky traps proving that the myco-insecticides worked as predicted. Climatic conditions were different in 2007: temperature averaged 15.9°C (16th May - 4th July), total precipitation was 281 mm. In 2007 only Naturalis-L was tested: with five applications an efficacy of 73% and 78% was obtained on the cherry varieties Langstieler and Dolleseppler, respectively. However, for the latest ripening and most infested variety Schauenburger only an efficacy of 18% was observed. In these cherries a high number of young larvae were found indicating that the efficacy was low at the end of the treatment period. In conclusion a control of R. cerasi with myco-insecticides seems possible. However, application regime still has to be improved and should not only be adapted to the flight period of R. cerasi, but also to the cherry varieties.