The occurrence of Xylosandrus compactus and its associated fungi on cacao from South Sulawesi, Indonesia: A preliminary study of an emerging threat to the cacao industry

Abstract

Xylosandrus compactus is 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 cacao in 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. compactus on 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.