Abstract: Especially in organic agriculture, Cydia funebrana (Plum fruit moth) is a serious pestof plum fruits. Therefore, we investigated whether the insect can be controlled by artificialhideouts treated with conidia of entomopathogenic fungi. Because we were not able to establish amass rearing of C. funebrana we did additional experiments with the related species Cydiapomonella, Cydia molesta and Eupoecilia ambiguella. In previous experiments we proofed thatcorrugated cardboard and bark mulch substrates were accepted for pupation. Additionally, weinvestigated the effect of water and oil based formulation of conidia of Beauveria bassiana. Thepresented data demonstrate that vegetable oils have a dramatic effect on larvae and oil-basedformulations can improve the efficacy of entomopathogenic fungi. In case of C. pomonella amortality of 46% and 92% was determined for Tween80 and sunflower oil, respectively. Theaddition of Beauveria bassiana conidia did not enhance the mortality but even when lowconcentrations of conidia (104conidia/ml) were applied in oil, 90% mycosis was achieved. Incontrast high concentrations of conidia were needed to achieve at least 70% mycosis whenformulated in water containing Tween 80. In further experiments we compared the efficacy ofB. bassiana conidia formulated in sunflower and rape oil. The results demonstrate that both oilscaused a high larval mortality and that the mycosis of the larvae was significantly higher whenconidia were formulated in rape oil. As we did not achieve high mortality with B. bassiana, wetested other entomopathogenic fungi like Lecanicillium lecanii, Isaria fumosorosea andMetarhizium anisopliae. M. anisopliae and I. fumosorosea caused the highest mortality to allmoth species. Furthermore, C. pomonella seems to be more sensitive to entomopathogenic fungithan C. funebrana. In additional experiments we investigated the persistence of M. anisopliaeformulated in oil or water and two I. fumosorosea isolates formulated only in water on chippedwood under natural conditions. The results demonstrate that the oil itself maintained its efficacyover the observed time of two months. Furthermore, the efficacy of the three tested isolated in thewater based formulation was influenced by the weather condition. Better results were obtainedwith I. fumosorosea compared to M. anisopliae.