Introduction

Abstract

Prior to the pine wood nematode (PWN) being shown to be the causal agent of pine wilt disease, the widespread death of pines in Japan had been attributed to bark and wood boring insects, especially coleopteran insects in the families Cerambycidae, Curculionidae, and Scolytidae. However, during a national project (1968–1971) to find a control for the problem it was shown that such insects, which supposedly had been responsible for killing the trees, could not lay their eggs in healthy pine trees, and also that the trees were wilting prior to insect attack. Consequently, the goals of the project had to be changed from focusing just on insects as causing the mortality to looking at other possible causes such as microorganisms, edaphic, tree physiological, and climatic factors.