The 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.

Identification and genetic diversity of two invasive Pissodes spp. Germar (Coleoptera: Curculionidae) in their introduced range in the southern hemisphere

“…The establishment of the pitch canker fungus, F. circinatum, in nurseries, established and mature Pinus plantations in South Africa (Coutinho et al, 2007;Mitchell et al, 2011;Wingfield et al, 2008) and its presence in South America (Wingfield et al, 2008), undoubtedly increases the importance of these two invasive Pissodes spp. It is therefore worthwhile investigating the role of Pissodes sp.…”

Selection of Pinus spp. in South Africa for tolerance to infection by the pitch canker fungus

“…Relative to alternative species, such as P. tecunumanii and P. maximinoi, the easy accessibility of seed makes P. elliottii an attractive alternative to P. patula. However, it should be cautioned that the slower growth of P. elliottii compared to P. patula (Morris and Pallett 2000) could cost more than the cost that F. circinatum might cause to P. patula (Mitchell et al 2011).…”

“…The disease has now spread to most pine growing nurseries in the country where it is managed with varying degrees of success. The most significant effect of F. circinatum on P. patula, however, can be seen on young seedlings that become infected and die after establishment (Crous 2005;Mitchell et al 2011). More recently, pitch canker was discovered on mature P. radiata and P. greggii trees in the Southern and Eastern Cape provinces of South Africa (Coutinho et al 2007;Roux 2007).…”

“…In the long term, tree breeders in South Africa hope that the tolerance of P. patula to F. circinatum could be improved by including tolerance as a selection criterion in their breeding programmes (Mitchell et al 2011). In the shorter term the tolerance of P. patula can be improved through hybridization with more tolerant species.…”

“…In the shorter term the tolerance of P. patula can be improved through hybridization with more tolerant species. The simplest immediate solution, however, is to deploy alternative species that are known to be tolerant to infection by F. circinatum, at least in high-risk sites (Mitchell et al 2011). …”