The Polyphagous Shot Hole Borer (PSHB) is a small beetle from South-East Asia that was first found in South Africa in 2017 and carries a fungus that damages the vascular system of trees it attacks.
The Polyphagous Shot Hole Borer Beetle (PSHB), Euwallacea whitfordiodendrus, was incorrectly identified as E. fornicatus when it was first discovered within South African borders in the National Botanical Garden of Pietermaritzburg in 2017. This species, originally from South-East Asia, has now spread to 8 out of the 9 provinces. This beetle is one of four species of beetle in a species complex which has strong associations with Fusarium fungi.
In its native habitats, the PSHB bore through the bark, into the sapwood of stressed trees, creating tunnel systems called galleries, within the vascular system of the trees. When outside their native range, the PSHB has been observed to attack healthy trees without much discrimination. The PSHB does not feed on the sapwood itself, but adult females carry spores of the fungus Fusarium euwallacea, which are inoculated into the galleries to grow as a food source for the beetle larvae.
Adult female beetles measure around 2 mm in length and are bigger and darker than males. Males are flightless. These beetles have a wide diversity of host trees but only reproduce in certain native and exotic species. Infected trees can contain more than 100,000 individuals, with females able to fly up to 1 km from their original tree.
Due to damage in the vascular systems of affected trees, branch dieback can start, followed by greater vulnerability and ultimately death. PSHB can survive in dead wood for up to 12 months. The original source reports that human movement between regions is an important vector for spread.
Frequently asked questions
What is the Polyphagous Shot Hole Borer (PSHB)?
PSHB is a beetle, originally from South-East Asia, that bores into the sapwood of trees. Adult females carry spores of the fungus Fusarium euwallacea, which grows in the tunnels as food for the larvae.
When was PSHB first found in South Africa?
The original source says it was first discovered in 2017 in the National Botanical Garden of Pietermaritzburg.
How does PSHB harm trees?
Damage to the vascular system can cause branch dieback, then greater vulnerability and ultimately death of the tree.
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