Association ofDiplodia pineawith a Root Disease of Pines in South Africa

Abstract

WINGFIELD, M. J., and P. S. KNOX-DAVIES. 1980. Association of Diplodiapinea witha root dise3sc of pines in South Africa. Plant Disease 64:221-223. Diplodia pinea is an important factor in a root disease of Pinus eJ/iotljj and P. taeda in various parts of South Africa and Swaziland. All stands in which the dise3se occurred were severely stressed. Diplodia pinea (Desm.) Kickx occurs throughout the conifer-growing areas of the world and is associated with a wide range of symptoms, including bark cankers, bud wih, dead top, seedling blight, seedling collar rot, staghead, and twig blight (1,3,4,9,12). In South Africa, D. pinea causes serious dieback of Pinus patula Sch!. & Cham., P. pinaster Ait., and P. radiata D. Don. after hail (5,7,8) and is regarded as the most important pathogen of pine plantations (8,15). Control is largely by restricting planting of susceptible species to areas where hail iamage is limited (5,6) and by replacing ISceptible species with the more tolerant elliottii Engelm. and P. taeda L. in the summer rainfall area (5-7). Since 1975, extensive losses have been caused by a root disease in P. taeda plantations belonging to the Usutu Pulp Company in Swaziland (D. G. M. Donald, personal communication). During a preliminary survey of local forest tree diseases, the senior author examined the diseased trees in Swaziland and observed similar symptoms on P. elliottii and P. taeda plantings in various parts of South Africa. This paper describes the association of D. pinea with Part of an M.Sc. thesis to be submitted by the senior author to the University of SteUenbosch. Accepted for publication 17 September 1979. 00191-2917/80/000050$03.00/0 01980 American Phy1opathologicaJ Society