South-east Asian borer invading KZN trees

A DESTRUCTIVE borer is eating away at indigenous and exotic trees in South Africa, across KZN’s various habitats from the Berg to the beach.

Durban environmental consultant Johan Bodenstein told the Independent on Saturday that the polyphagous shot hole borer, indigenous to south-east Asia, was being countered in the US using a chemical that is not registered in South Africa.

“People are taking their own initiative buying chemicals and experimenting,” he said.

He found the most effective way of destroying the borer to be chipping the tree and composting it, or burning it.

Destroying the bug was important because, once established in living wood, it could survive if that wood died, but it would not invade wood that was already dead, such as house rafters and furniture, he said.

Bodenstein said the borer deposited a fungus in the trees that interfered with the movement of water and nutrients in the tree.

A symptom that commonly shows trees are infected is the sight of dead branches at the top of the tree.

Bodenstein said he had picked up borer infection in 32 different tree species in KZN. In Durban, they occurred in trees in the city’s open spaces, gardens and in Glenwood’s Pigeon Valley Nature Reserve.

eThekwini Municipality said it still needed time to gather information on the polyphagous shot hole borer and would respond when it had done so. The national Department of Agriculture did not answer our queries about the chemicals not being registered.

Bodenstein said palm trees, as well as species of the indigenous genus Euclea, appeared to be exempt from infection, while commercial, fruit-bearing trees such as avocados and pecan nuts were vulnerable.

He said the borer was able to survive the cold because it isolated itself from the elements by being embedded inside the wood. The coldest habitat in which he had identified it was the Champagne Valley in the Drakensberg.

He said he had seen it mostly in coastal areas.