Integrated Oak Timber Protection from Ambrosia Bark Beetles: Economic and Ecological Importance in Harvesting Operations

Ambrosia bark beetles belong to a group of xylomycetophagous insects from the order Coleoptera, family Curculionidae and are characterized as important pests of oak timber. Galleries they form during their life cycle and infect with »ambrosia fungi« significantly decrease the economic value of oak roundwood. A state owned Croatian company »Hrvatske šume« Ltd. manages FSC certificated forests, where pedunculate and sessile oaks account for 22.6% in the annual allowable cut. Methods of oak roundwood protection, that used to be implemented in the past, are now banned in accordance with EU legislation as well as FSC criteria of forest protection. In these forest management conditions, it becomes necessary to introduce new biotechnical methods for oak roundwood protection. Available commercial products, flight barrier traps and synthetic semiochemicals, as well as pretreated insecticide treated polymer nets, were tested as means of integrated oak roundwood protection. Implementation of these products was tested in field conditions. Good knowledge of phenology of ambrosia bark beetles, thorough understanding of timber harvesting operations and field conditions that dominate in even aged oak forests, is crucial if applied methods are to be effective and taken on time. Field experiments conducted in this research showed that early seasonal deployment of semiochemically baited flight barrier traps can reduce the number of bark beetles that infest oak timber. It was also concluded that without additional protection with polymer nets, it is not possible to protect oak timber in compliance with strict FprEN 1316-1: 2012 E standards for oak roundwood classes, which do not allow any timber infestation in the highest quality grades (A and B quality class). Semiochemicals used as repellents during the research were ineffective. In the early months of spring, oak roundwood is at high risk of infestation at the roadside landings, where it is waiting to be transported.