Artificial hideouts with entomopathogenic fungi: A strategy for biological control of the plum fruit moth Cydia funebrana?

Especially in organic agriculture, Cydia funebrana (plum fruit moth) is a serious pest of plum fruits. Therefore, we investigated whether the insect can be controlled by artificial hideouts treated with conidia of entomopathogenic fungi. Because we were not able to establish a mass rearing of C. funebrana we did additional experiments with the related species Cydia pomonella, Cydia molesta and Eupoecilia ambiguella. In previous experiments we proofed that corrugated cardboard and bark mulch substrates were accepted for pupation. Additionally, we investigated the effect of water and oil based formulation of conidia of Beauveria bassiana. The presented data demonstrate that vegetable oils have a dramatic effect on larvae and oil-based formulations can improve the efficacy of entomopathogenic fungi. In case of C. pomonella a mortality of 46% and 92% was determined for Tween80 and sunflower oil, respectively. The addition of Beauveria bassiana conidia did not enhance the mortality but even when low concentrations of conidia (104conidia/mL) were applied in oil, 90% mycosis was achieved. In contrast high concentrations of conidia were needed to achieve at least 70% mycosis when formulated in water containing Tween 80. In further experiments we compared the efficacy of B. bassiana conidia formulated in sunflower and rape oil. The results demonstrate that both oils caused a high larval mortality and that the mycosis of the larvae was significantly higher when conidia were formulated in rape oil. As we did not achieve high mortality with B. bassiana, we tested other entomopathogenic fungi like Lecanicillium lecanii, Isaria fumosorosea and Metarhizium anisopliae. M. anisopliae and I. fumosorosea caused the highest mortality to all moth species. Furthermore, C. pomonella seems to be more sensitive to entomopathogenic fungi than C. funebrana. In additional experiments we investigated the persistence of M. anisopliae formulated in oil or water and two I. fumosorosea isolates formulated only in water on chipped wood under natural conditions. The results demonstrate that the oil itself maintained its efficacy over the observed time of two months. Furthermore, the efficacy of the three tested isolated in the water based formulation was influenced by the weather condition. Better results were obtained with I. fumosorosea compared to M. anisopliae.