Crown wilt of Pinus radiata associated with Diplodia pinea infection of woody stems

Abstract Crown wilt of Pinus radiata associated with Diplodia pinea infection of woody stems, normally highly resistant, was noticed in a number of incidences in recent years. Typical Symptoms are inner bark necrosis, blue‐staining of wood and its subsequent desiccation which can lead to blockage of water transport, hence crown wilting. Suspicion about the emergence pf an aggressive strain of the pathogen as cause for the disease outbreak is not supported by experimental evidence. Severe incidences of the disease were noticed to be associated with prolonged drought; in pot trials woody stems of P. radiata became infected only when needle water potential dropped to –2.5 MPa, none of the other methods of predisposition tried had any effect on infection.