Investigating bark, ambrosia and nitidulid beetle (Coleoptera : Scolytinae and Nitidulidae) communities and their potential role in the movement of Ceratocystis manginecans in commercial forestry plantations in Riau, Indonesia

Abstract

Ceratocystis Canker and Wilt Disease (CCWD), caused by the fungal pathogen Ceratocystis manginecans, poses a significant threat to Acacia and Eucalyptus plantations in Indonesia. Infections typically occur through wounds on the main stems of trees, and infected trees, particularly Acacia, are often co-infested by various wood-associated beetles. The aim of this study was to identify the beetle species associated with Ceratocystis-infected trees and to assess their potential role in dispersing C. manginecans. Beetle and frass samples were collected from Ceratocystis-infected compartments of Acacia and Eucalyptus propagated as monocultures in Riau, Indonesia, either by using traps or by direct collection from infected trees. The samples were screened for the presence and viability of Ceratocystis propagules using a quantitative polymerase chain reaction-high-resolution melting analysis (qPCR-HRMA) diagnostic tool and a carrot baiting technique, respectively. Fourteen beetle species, predominantly collected from traps, representing nine genera of the Scolytinae and Nitidulidae, were identified from the two plantation types. The qPCR tool detected the presence of Ceratocystis DNA on 13 of the 14 beetle species at concentrations as low as 0.015–0.0019 ng. However, viable Ceratocystis propagules could not be recovered from these beetles using culture-based methods. Of the 105 frass samples screened, qPCR detected Ceratocystis DNA in 67 samples; however, only one Ceratocystis isolate was obtained using the carrot baiting method. The results of this study suggest that the beetles and beetle frass can harbour Ceratocystis propagules, as indicated by the detection of fungal DNA. However, the viability of the propagules and the ability of the beetles and/or beetle frass to spread C. manginecans requires further investigation.