Reducing Pest Risk in Birch Wood Products—The Effective Heat Treatment for Bronze Birch Borer Agrilus anxius (Coleoptera: Buprestidae) Prepupae

Abstract

The protection of forest resources and the safe trade of forest products require phytosanitary measures to reduce the risk of pest movement to novel environments. Heat treatment is a widely available, efficient and effective method to produce phytosanitary wood products destined for trade. Defining the minimum effective heat treatment dose required to cause the mortality of insects in wood products reduces the risk of spreading pests to novel environments with the lowest possible energy cost, which in turn reduces environmental impacts and provides confidence in current guidelines for heat treatment regulations. The minimum effective heat treatment dose (time and temperature) for Agrilus anxius (bronze birch borer) prepupae was determined using the Humble water bath applying heat in vitro. Heat treatment was assessed using a controlled increase in temperature to simulate the heat ramp applied to wood in industrial kilns and conventional heat chamber operations. Target temperatures between 51°C and 56°C for exposure durations of 15 and 30 min were tested to determine the minimum effective dose. Prepupal A. anxius did not survive exposure to 53°C, 54°C, 55°C or 56°C for 30 min or 54°C and 56°C for 15 min. Chronic or delayed mortality was observed at 53°C for 15-min treatments. Evaluating the effect of specific heat treatment parameters for other forest pests is recommended to identify and validate the minimum temperature and time required to cause the mortality of wood pests in order to avoid introducing non-indigenous species with wood products and limit pest movement.