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Abstract
The feasibility of using commercial 2.45-GHz microwave equipment to kill cerambycid larvae and pine wood nematodes (PWN) [Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle] infesting lumber was investigated. Research goals were to test a system of separating green material into moisture content (MC) ranges and to determine the feasibility of using internal wood temperature as the critical lethal treatment parameter. Prior research suggested that MC is a critical factor to consider in scaling up from laboratory-scale experiments with small volume specimens to full-sized lumber using commercial treatment processes. Commercial units used for this study were a chamber design unit for batch irradiation treatment and a continuous conveying tunnel design of microwave equipment fitted with optional air heaters. Because red pine is a preferred host of PWN and has high wood MC, microwave irradiation trials were conducted with red pine directly obtained from freshly sawn logs. The trials conducted using batch irradiation resulted in 100-percent mortality in all treated red pine materials (4- by 4- by 20-in cant samples) infested with PWN or beetle larvae above a measured wood temperature of 62°C, regardless of wood MC. In contrast, treatment of 1-inch-thick boards using continuous feed microwave irradiation achieved 100-percent morality at lower wood temperatures. These results were encouraging and indicate commercial microwave (2.45 GHz) treatment may be a feasible alternative to conventional heat treatment or methyl bromide fumigation.
Commercialization of microwave processes to eradicate exotic pests infesting lumber may provide a useful tool for nations endeavoring to exclude these invasive pests from inadvertently crossing their borders in wood pallets and crates or other forms of solid wood packing material. Introduction of pine wood nematodes (PWN) [Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle] and cerambycids, such as the Asian long-horned beetle Anoplophora glabripennis (Motsch.) (Coleoptera: Cerambycidae) (ALB) into new habitats threaten forest resources around the world (USDA APHIS 1998, Nowak et al. 2001, Krehan 2002, Mota et al. 1999). PWN causes a serious wilt disease in several pine species and is vectored by cerambycids (Wingfield et al. 1982). Currently, kiln treatment and methyl bromide fumigation are the only two sanitization treatments internationally approved for solid wood packing materials under the auspices of the United Nations (U.N.) (UN FAO 2002). However, the U.N. phytosanitary commission is also seeking...