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Xylosandrus compactusis one of the significant beetle pests on perennial crops, which has become an increasing problem on cacao productivity and sustainability in South Sulawesi, Indonesia. The beetle is also known as ambrosia beetle due to the obligate association with symbiotic fungi. The beetle and infested plant parts were collected from infested Theobroma cacaoin the field, then the beetles identified morphologically and the associated fungi isolated. In this study, we found that the beetles attacked all stages of cocoa growing in the field such as seedling, young trees and mature trees with visible symptoms including the appearance of round bore holes with powdery frass on the tree trunk and branches. Also, we found the beetle being distributed in three main cocoa areas in South Sulawesi. According to the beetle´s characteristic, the female has the black colour of the body (head and elytra), size 1–2 mm and the shining slope. Six types of fungi were isolated from infected plant parts and the beetle X. compactus: Fusarium-like colony (two isolates), Lasiodiplodia-like colony, Ceratocyctis-like colony and Diaporthe-like colony (two isolates). Among the fungi isolated, several fungi were known as the pathogen. The beetle and its associated fungi are responsible for the typical dieback symptoms, decline and sudden death inflicted on a number of cacao trees. The occurrence of X. compactuson cacao tree is reported for the first time from Sulawesi, Indonesia. The beetle pest infestation will become a significant threat to the future of the cacao industry in Sulawesi, Indonesia.

Endophytic strains of Trichodermaspecies can be used as an alternative to chemicals to control vascular streak dieback (VSD) disease of cacao. Of 21 Trichodermaisolated from Theobroma cacao(cacao) in Indonesia, 19 were identified as Trichoderma asperellum. Four isolates of this species (ART-4, ART-5, ART-6 and ART-8) were reintroduced into young cocoa seedlings by root inoculation and after 4 weeks all were recovered from roots and stems, while ART-4 and ART-5 were recovered from leaves as well. Spraying seedlings pre-inoculated with T. asperellumART-4, ART-5 and ART-6 with mycelium of the VSD pathogen Ceratobasidium theobromaeresulted in no apparent VSD symptoms on the leaves. Those seedlings pre-inoculated with ART-8 showed 8.9 % incidence of VSD symptoms on the leaves when compared to a 20.4 % incidence of VSD on positive control leaves, 12 weeks after inoculation. The same isolates were also reintroduced into 3-month-old cocoa seedlings via the connecting site following shoot grafting, and after 12 weeks all isolates were recovered from stem and leaves. Seedlings grafted with buds infected by VSD and treated by ART-4 showed no VSD symptoms on their leaves 12 weeks after grafting and inoculation. However, those treated with ART-5, ART-6 and ART-8 showed 33.3 %, 50.0 % and 56.0 % incidence of VSD symptoms on their leaves, respectively, compared to an 88.9 % incidence of VSD on positive control leaves. Therefore, the study results demonstrates for the first time the potential of T. asperellumisolates to control VSD disease on cacao.