Arborist offers residents valuable lessons on how to identify trees affected with shot hole borer in Glenferness

Fourways Review got the privilege of attending a tree walk in Glenferness hosted by the Greater Kyalami Conservancy. Anton Moller of Arbor Africa shared his specialist knowledge of tree care and taught Kyalami residents how to identify trees infected with shot hole borer, which has affected trees in eight of the nine provinces around South Africa.

This infestation is reportedly a huge concern in the City of Joburg, thought to be the biggest urban forest in the world. It is believed that the borer arrived on infected shipping crates from South East Asia, where trees have a developed a natural resistance to it. As a new pest in South Africa, its introduction is devastating to trees susceptible to the fungus the borer carries and feeds on. It is the fungus that kills the trees. Many London Planes, Oaks and other popular street trees in Joburg have already died.

While any tree can be infested with the borer, some, such as the Jacaranda, are surviving, although both indigenous and exotic trees have succumbed to the infection.

A number of treatments are currently being used to control the borer and the fungus it produces, but these can also cause varying degrees of damage to the surrounding environment. Stressed trees tend to be the first victims, so residents are advised to mulch and ensure trees are watered correctly. Residents are also urged to regularly check on their trees as it might be an indicator if the borer reaches their property.

The spread of the borer is assisted by transporting infected wood, and this includes firewood. Moller further advised those attending to ensure firewood is dry.

“If you see tiny holes in live or fresh wood it is likely carrying the beetle. If infected trees have become a host and you cannot place two hands on the tree without covering the holes, they should be cut down and disposed of. Burning or solarising a tree can kill the beetle, as does chipping the wood immediately after the tree is felled. The holes are small, roughly the size of a sesame seed. Nearly all dead wood is affected by some type of borer, however the shot hole borer is unique in that it affects live wood. If you suspect you have a tree affected, please ensure that you get specialist advice.”

Indications so far are that, if detected early, trees can be treated with a systemic fungicide. In theory, the borer can be discouraged from attacking a specific tree by treating the tree with a systemic insecticide. The efficacy of any treatment is still being investigated.

Arborist Anton Moller can be contacted on 083 600 9786 or Arbor8733@gmail.com

Moller shared management strategies:

• Remove and destroy severely infested trees. This is very necessary. These trees are not likely to survive, and are the breeding hosts, from which large numbers of young borers will emerge looking for another host to infest.

• Some trees may have only a few branches and limbs infested. It may be possible in these cases to remove only the infested limbs.

• Identify and treat: Young trees with low infestation levels; trees displaying some resistance to the borer and/or its fungal symbiont (‘healthy’ trees with evidence of borer activity over a longer time); Uninfested high value preferred host species (prophylactic treatment)

• Recommend measures, which may include irrigation, mulching and fertilizing, to improve the health and vigour of all trees as far as possible.

• Reassess regularly (every 2 months, during warmer weather, if possible).