Pitch canker fungus, Fusarium circinatum : implications for South African forestry

Abstract

Fusarium circinatum, the causal agent of pitch canker of mature pines and root/collar rot of pine seedlings/cuttings, has resulted in large-scale losses to pine forestry in various parts of the world. The disease caused by this fungus is now regarded as one of the most important threats to pine plantations by a pathogen. Fusarium circinatum was first discovered in South Africa in 1990 where it infected Pinus patula seedlings in a nursery. Subsequently, the pathogen spread to pine nurseries in all other parts of the country, where it affects several Pinus species. Fusarium circinatum then appeared in the field where it has resulted in large-scale mortality of mostly young P. patula seedlings after planting. Pitch canker first appeared on mature P. radiata in 2006 and sporadic outbreaks of the disease have occurred subsequently on this species and on P. greggii in the western, southern and north-eastern Cape. Pinus patula is the most important softwood species grown in South Africa, comprising 50% of all softwoods planted, and is highly susceptible to F. circinatum. The pathogen, therefore, poses a potentially devastating threat to the future sustainability of the South African softwood industry. Strategic measures to minimise further spread are urgently needed. This review presents an overview of the impact that F. circinatum has had on South African forestry, and it considers the long-term prospects for pine forestry in the country as this relates to the presence of the pitch canker fungus.