Pinewood nematode presence and survival in commercial pallets of different ages

Abstract

The pinewood nematode (PWN) Bursaphelenchus xylophilus is an important forestry quarantine organism in the world and can be disseminated through the international trade of infested wood packaging materials. Although heat treatment (HT) and kiln-drying (KD) are used to disinfest the wood and reduce its moisture, doubt remains if treated wood can be re-infested and support viable populations of the nematode. In this study, the risk associated with disseminating the PWN with kiln-dry pallet timber was evaluated by sampling commercial pallets of different ages and by inoculating B. xylophilus into treated wood to assess the nematode’s survival. A total of 229 timber samples (boards and blocks) were randomly sampled, finding no Bursaphelenchus species. Nematodes of the families Aphelenchidae, Aphelenchoididae, Diplogasteridae, Rhabditidae and Tylenchidae were found in 45% of the samples, being absent from timber with less than 6 months but present with increasing frequency in older pallets. Fungi were encountered frequently, with the genus Trichoderma dominant. In the second trial, artificial inoculations of B. xylophilus were made in pallet timber of different age and assessed after 7, 14, 28, 56 and 84 days. The PWN was recovered in the first sampling, but infestation rates and nematode numbers decreased until disappearing in the subsequent samplings. The results confirm that ISPM 15 treatments effectively sanitize wood, and older, drier wood does not support re-infestation with B. xylophilus, while other saprophitic nematodes and fungi colonise the treated timber. Future research should evaluate the risk associated with KD timber subjected to rewetting and its ability to support viable populations of the PWN.