Mechanism of cavitation development in the pine wilt disease

Abstract Volatile terpenes increase in xylem tissue after infection of Pinus thunbergii with the pine wood nematode ( Bursaphelenchus xylophilus ). The role of these terpenes in traeheid cavitation, which blocks xylem‐sap ascent and leads to water deficit in pine trees, was assessed. Volatile terpene concentration increased long before initiation of tracheid cavitation. After the volatile terpenes reached the highest concentration, severe cavitation developed. Direct injection of α‐pinene into healthy pine trunks formed artificial cavitation in xylem. These observations support the hypothesis that excessively produced volatiles, which are hydrophobic and have lower surface tension than water can promote tracheid cavitation in pine wilt disease.