Polyphagous shot-hole borer (PSHB), Euwallacea sp. is an invasive beetle that attacks dozens of common native and landscape trees. The tiny beetle tunnels into host trees and spreads Fusarium dieback (FD), a disease known to infect over 110 tree species. FD is caused by Fusarium euwallaceae, a fungus that disrupts the transport of water and nutrients in the tree, leading to branch dieback and overall decline

Entry Hole

The typical entry-hole to a PSHB gallery is perfectly round and about 0.85 mm in diameter, or about the size of the tip of a ballpoint pen. The abdomen of the female beetle can sometimes be seen protruding from the entry-hole. It may also be plugged or covered by sap, exudate, or frass (sawdust from boring) from the tree.

Symptoms of Attack

Entry-holes are typically accompanied by attack symptoms, which are the host tree's visible response to stress. These symptoms (and examples of species that produce them) include:
• Staining: may be wet and dark OR dry and light-colored
• Gumming: thick resin that sometimes pushes the beetle out of the gallery • Sugary exudate: may form white, powdery "volcanoes"
• Frass: produced by the beetle's boring activity, may be present on any host tree depending on the infestation level
Some of these symptoms may be washed away or obscured by rain or irrigation water

Branch Dieback

Advanced infestations lead to branch dieback and overall decline. Watch for beetle attacks concentrated on a branch or in the branch collar (the point of attachment between the main trunk and a branch)—infestations in this area can lead to limb failure.

Signs of Infection

Fusarium causes dark discoloration of the wood beneath the bark and around the beetle gallery. Lightly scraping away the bark around the entry-hole will reveal the dark brown to black staining.
Information obtained from pshb.org
For more information and affected tree hosts in South Africa, visit the FABI webpage on https://www.fabinet.up.ac.za/pshb

In the News

Cropwatch Africa Surveys in the Kruger National Park for PSHB:

PSHB Trapping station

PSHB Trapping stations in the Kruger National Park

PSHB Trapping data collected

Project funded by USDA APHIS with logistic support from SANParks