Invasive tree pathogens and pests in South Africa: can we stem the tide?

Invasive tree pathogens and pests in South Africa: can we stem the tide?
Jolanda Roux, Michael J. Wingfield
Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa

The past decade has seen a significant increase in the number of insect pests and plant pathogens (pests) of tree species in South Africa. In the last five years the Myrtaceae rust pathogen, Puccinia psidii, the Cycad Asian Scale (CAS), Aulacaspis yasumatsui, and several damaging insects pests of plantation forestry species appeared in the country. The previously recorded non-native pathogens, Phytophthora cinnamomi and Armillaria mellea has spread into natural environments, threatening native ecosystems.  These, and other pathogens, most likely entered the country on infected plant material and/or soil.

The unregulated trade in non-native ornamental plants is a major contributer to the local spread of pests in South Africa. The spread of CAS, for example, has been accelerated by the nursery and collector’s trade and is resulting in large populations of CAS, posing a threat to the survival of native South African species.

It is crucially important that the South African public be sensitized to the threat that invasive alien pests pose to the natural environment. Here, responsible trade in plants is a key issue.  Quarantine regulations must be emphasised and actively communicated, alongside law enforcement. Experience from other countries has unequivocally illustrated the fact that a failure to take a strong stand on quarantine and the management of the trade in non-native plant species will result in South Africa losing important components of a rich and irreplaceable native plant biodiversity and the associated ecosystems in which this natural resource occurs.