|
Recently we had the privilege of hosting a speaker, Paul Barker, who works closely with identifying and eradicating the Polyphagous Shot Hole Borer The Polyphagous Shot Hole Borer (PSHB) is an invasive beetle native to Southeast Asia that has seriously threatened South Africa's trees. The first detection was in 2017 on London Plane trees in the KwaZulu-Natal National Botanical Gardens in Pietermaritzburg. The PSHB has since spread to multiple locations across eight provinces. This tiny beetle, about the size of a sesame seed, may seem insignificant, but it carries with it a deadly companion: the fungus Fusarium euwallaceae. The beetle has a symbiotic relationship with this fungus, which it uses as a food source for itself and its larvae. Unfortunately, this fungus is also a tree killer. In susceptible trees, it causes a disease known as Fusarium dieback, which leads to dying branches and, ultimately, tree death.  The Threat to South Africa's Trees PSHB poses a significant risk to a wide range of exotic and indigenous trees in urban, agricultural, and natural landscapes. While the beetle attacks many tree species, it cannot complete its life cycle on all of them. Trees in which the beetle can breed and multiply are known as "reproductive host trees." These include important species such as oaks, maples, willows, coral trees, avocados, and castor beans. On these trees, the beetle establishes galleries (tunnels) where it breeds, and the fungus it carries can thrive, leading to severe damage or tree death. Conversely, there are "non-reproductive host trees" where the beetle may attack but does not establish galleries or breed. The fungus may or may not cause disease on these trees, and they are generally not expected to die. However, the presence of the beetle on any tree is a cause for concern due to the potential for the spread of the fungus. Species at Risk Among the species where both the beetle and fungus flourish are the Box Elder, Weeping Willow, English Oak, and Castor Bean. However, these are not the only species at risk. The PSHB and its associated fungus have been found in a wide variety of tree species across South Africa. For a complete list of affected species, please refer to the attached documentation. Please see attached documents for full plant species lists and more information. Preventing the Spread of PSHB One of the most significant means of spreading this beetle is the movement of infested wood, most importantly, firewood. Proper disposal of infested trees is crucial in reducing the spread of this damaging pest. Methods such as chipping, composting, or solarization of wood are recommended to prevent further infestation. Solarization can be achieved by placing chips in direct sunlight and covering the pile with plastic. Burning is not recommended as the smoke and heat will make the beetles disperse out of the wood before burning is completed. Ongoing surveys are being conducted to monitor the spread of the PSHB across South Africa. Public awareness and involvement are vital to this effort. You can assist by keeping an eye out for symptoms of infestation in your local area and reporting any suspicious activity to the relevant authorities. What You Can Do
By staying informed and vigilant, we can help protect South Africa’s trees from the devastating effects of the Polyphagous Shot Hole Borer. Remember - Burn it where you buy it! 
0 Comments
The infestation of the shot hole borer beetle has spread to multiple places in Western Cape and poses a threat to indigenous trees throughout South Africa. Polyphagous Shot Hole Borer is a tiny beetle that feeds on living trees. It's difficult to see the beetle. The females are black in color and (1.8-2.5) mm long and males also small but brown and wingless. The males are 1.5-1.7 mm and are less common than females.  Polyphagous: Shot Hole Borer beetle The beetle needs breeding and feeding space and enters a tree through the bark, creating breeding and feeding lines, with a layer of spores of the fusarium fungus. The shot hole borer beetle has a symbiotic relationship with this fungus because it is the beetle's primary food source. To reproduce and eat fusarium fungus, the beetle digs tunnels deep within the infected tree. The beetle does not kill the tree but the fungus (Fusarium Euwallacea) does. The fungus spreads from the tunnel into the tree, obstructing the vascular system of the tree. This fungus is the main causes of tree wilting. The Shot Hole borer beetle is native to Southeast Asia. It arrived in South Africa in 2017 and has caused some environmental damage. It reproduces in both exotic and native tree species. Outside of its native habitat it appears to be much more aggressive. The symptoms of infected trees differ from one tree species to another, and there are numerous signs that a tree is infected. Some of these indicators could be sawdust collecting on the bark and around the base of the tree. Certain tree species may experience leaking of liquid and gum from beetle holes. Most people will not notice the problem until the tree dies. As a result, the wood from the dead infested tree must be processed to kill the beetle inside; otherwise, the surviving beetles will move to nearby trees and spread the infection. You have a few options for dealing with the dead wood. If possible, solarizing an infested wood pile and burn the wood right away. Alternatively, one can also chip the wood.  Make sure to dispose of infected wood safely We can't completely stop the infestation of shot hole borers, but we can treat and manage it to lessen its impact and spread. If you grow trees and observe tree wilting, try to determine whether the symptoms are caused by Shot Hole Borer. If a tree is heavily infested, it should be cut down and destroyed. If the main stem is unaffected, infested branches can be removed. Dump wood at a designated dumping site or inquire with the municipality. If you chip the wood finer than 5cm, you can make compost or burn it on-site. Note that some beetles will flee if the wood becomes hot or there is smoke so make sure to contain the burn area and burn at a high enough temperature. As we approach the festive season when we all like to make braais at our holiday destination, please do your part and DO NOT MOVE FIREWOOD around, especially if you live in an infested area. We recommend that you rather buy invasive firewood at your local holiday destination and thereby supporting the local rural economies and helping to reduce the spread of invasive vegetation and the shot hole borer beetle. Make sure that the wood that you buy is invasive and that it is locally obtained. Note: All guests houses in the Grootvadersbosch Conservancy, including Cape Nature, do not allow external firewood to be brought in. Let us do everything we can to protect our forests and control the Shot Hole beetle infestation. References https://greenpop.org/polyphagous-shot-hole-borer-beetle/ https://www.fabinet.up.ac.za/pshb https://www.farmersweekly.co.za/crops/field-crops/protecting-south-africas-trees-from-the-shot-hole-borer/  Make sure that you buy local firewood this holiday season and help stop the spread |
AuthorGVB Conservancy Staff Archives
May 2026
Categories
All
|
||||||||||||||||||||
RSS Feed
