The Utility of Trichoderma spp. Isolates to Control of Xylosandrus germanus Blandford (Coleoptera: Curculionidae: Scolytinae)

Abstract

The invasive ambrosia beetle,Xylosandrus germanusBlandford (Coleoptera: Curculionidae: Scolytinae), is a serious pest of hazelnut in Turkey, which is the biggest hazelnut producer in the world. In this study, the utility of four isolates representing differentTrichodermaspecies (T. harzianum,T. hamatum,T. asperellum, andT. atroviride) was evaluated on survival, gallery behavior and brood production ofX. germanusby effecting the symbiotic fungal development at laboratory conditions. Hazelnut branches were exposed to fungal suspensions (1 x 10(6)and 1 x 10(8)conidia mL(-1)doses) for about 30 s. and transferred to individual plastic boxes. Ten healthy females ofX. germanuswere released into each box to determine the effect of the treatment of mycoparasite isolates. The antagonistic effect ofTrichodermaspecies on symbiotic fungus was evaluated in dual-culture experiments in Petri dishes. The survival and gallery production of the pest were not directly affected by treatment of two different doses of all fourTrichodermaspecies. The growth of the symbiotic fungus, however, was suppressed significantly byTrichodermaisolates in beetle galleries as well as on Petri dishes. Moreover, symbiotic fungal growth and eggs, larvae, and pupae of the beetle were not observed in the galleries carved out by females within the branches treated with two concentrations ofT. harzianum,T. asperellum, andT. atroviride. Some of the galleries in the branches treated withT. hamatumhad very sparse mycelial growth and fewer broods compared to the control. Our findings showed that theTrichodermaspecies may be potential biological control agents againstX. germanus.