Page 63 - University of Pretoria RESEARCH REVIEW 2018
P. 63

Forests at risk –
coming to grips with a tiny beetle
Wilhelm de Beer, Department of Biochemistry, Genetics and Microbiology, and Forestry and Agricultural Biotechnology Institute (FABI)
In the space of just over a year, between the discovery of the invasive Polyphagous Shot Hole Borer (PSHB) beetle in 2017, and its destructive path throughout 2018, it
has been confirmed present on 80 host tree species,
35 of which are native to South Africa.
The PSHB is an aggressive, 2 mm long ambrosia beetle that can attack many different species of trees. It bores through the bark to construct breeding tunnels (called galleries) in the sapwood. Each little beetle carries a specific fungus that is cultivated as a food source in these galleries. In the case of the PSHB, this fungus is a species of Fusarium that can kill the infected trees.
Dr Trudy Paap, a postdoctoral
fellow in FABI and the South African National Biodiversity Institute
(SANBI), discovered the beetle in Pietermaritzburg in early 2017 as
part of a routine survey of pests and diseases in the Botanical Gardens. A team of researchers at FABI, led by Professor Wilhelm de Beer, assisted in establishing a countrywide research network to resolve unanswered questions about the invasive beetle and its fungal symbiont.
For 15 years, Wilhelm de Beer’s research has been on fungal
Wilhelm de Beer at a coral tree killed by PSHB.
 associates of bark and ambrosia beetles, linked to the work of FABI’s Tree Protection Co-operative Programme, and involving collaborators from five continents. Thus, when the PSHB was detected in South Africa, FABI had the knowledge base and experience immediately
to confirm the beetle and fungus identities, using DNA sequencing technology.
What distinguishes the PSHB invasion from other tree pests is that it
affects so many different trees, in
the agricultural sector, in urban
forests and in natural forests. In an article published in Australasian Plant Pathology in 2018, some of the detail of this new invasion in South Africa was described.
Under the leadership of Professor de Beer, FABI has embarked on a number of research projects in collaboration with seven universities in South Africa. The aim is to provide science-based advice on the management of this destructive beetle to a broad range of stakeholders – government and the forestry industry, green industries, agriculture, and the general public.
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