Efficacy of commercial microwave equipment for eradication of pine wood nematodes and cerambycid larvae infesting red pine

Abstract

The feasibility of using commercial 2.45-GHz microwave equipment to kill cerambycid larvae and pine wood nematodes (PWN) (Bursaphelenchusxylophilus (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 equip- ment 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 mi- crowave irradiation achieved 100-percent morality at lower wood temperatures. These results were encouraging and indicate com- mercial microwave (2.45 GHz) treatment may be a feasible alternative to conventional heat treatment or methyl bromide fumigation.