PEER-REVIEWED ARTICLE bioresources.com Pipíška et al. (2021). “Juniper strandboards,” BioResources 16(2), 3886-3894. 3886 Utilization of the Western Juniper (Juniperus occidentalis) in Strandboards to Improve the Decay Resistance Tomáš Pipíška, a, * Jed Cappellazzi, a Scott Leavengood, a Frederick A. Kamke, a Gerald Presley, a and David Děcký b Naturally durable wood species such as western juniper (Juniperus occidentalis) are a potential source of bio-based wood preservatives for the improvement of non-durable timber species. This research investigated the durability of southern yellow pine (Pinus sp.) and western juniper lumber or strandboard. Single layer panels were made with six different types of wood or wood treatments: southern yellow pine, mixed juniper sapwood and heartwood, sapwood, heartwood, sapwood strands impregnated with juniper oil prior to and after panel manufacturing. Panels were fabricated with 560 kg/m 3 oven-dry density with 5% of PF resin and 0.5% of wax. Durability testing was performed with the brown rot fungi Gloeophyllum trabeum and Rhodonia placenta and the white rot fungus Trametes versicolor. Internal bond as a crucial parameter of OSB was measured. Tests revealed that juniper heartwood and juniper heartwood strandboards were highly decay resistant, and juniper oil pre- and post- impregnation strandboard manufacture imparted increased resistance to decay against one brown rot fungus, Gloeophyllum trabeum. Juniper strandboard manufactured from non-impregnated strands showed significantly higher internal bond than pine. These results suggest there is excellent potential for manufacturing highly decay-resistant OSB from juniper, especially from heartwood and that juniper oil can increase the durability of juniper sapwood strandboard. Keywords: Natural durability; Western juniper; Strandboard; Decay resistance; Internal bond Contact information: a: Department of Wood Science and Engineering, Oregon State University, 119 Richardson Hall, 3180 SW Jefferson Way, Corvallis, OR 97331, USA; b: Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, 613 00 Brno, Czech Republic; *Corresponding author: tpipiska@gmail.com INTRODUCTION Western juniper (Juniperus occidentalis Hook.) is an invasive tree species that is widespread in the western United States including Oregon, California, Washington, Idaho, and Nevada (Bedell et al. 1993; Swan 1995; Gedney et al. 1999). The wood has an average density of 497 kg/m 3 , with yellow sapwood and aromatic rose-red heartwood that is commonly used to manufacture posts, poles, fencing, decking, and other products (Panshin and Zeeuw 1980; Swan and Connolly 1998). The heartwood is highly decay-resistant and can remain in-service for 56 years or more without preservative treatment (Hemmerly 1970; Highley 1995; Swan 1995; Morrell and Schneider 1999; Morrell 2011; Kirker et al. 2013; Adams 2014). The durability of juniper heartwood is attributed to the high lignin content and presence of the cedrol and other terpenes that can be extracted by steam distillation (Kurth and Ross 1954; Adams 1987; Highley 1995). Sapwood has little inherent