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June : Mysterious fungus threatens local trees

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21 June, 2019

Mysterious fungus threatens local trees

Mysterious fungus threatens local trees
Bheka Nxele (Working for Ecosystems) and Errol Douwes (South African Wildlife Management Association)
check a tree for signs of fungal infection.

FRUIT- bearing trees in local orchards as well as indigenous trees face a threat as a fungus which lives in a symbiotic relationship with the Polyphagous Shothole Boerer Beetle is mysteriously spreading through South Africa - it has already been spotted in some avocado trees in backyards.

The beetle is thought to have originated in South East Asia.

Errol Douwes, senior manager for restoration ecology at the South African Wildlife Management Association recently gave a talk on the beetle at the Durban North Garden Club.

"It appears to be spreading quite quickly through South Africa. It effects a whole lot of different trees. There are many street trees that it breeds in that we are aware of and there is a growing list of indigenous trees that we are aware of as well," said Douwes.

While the beetle does not pose much of a threat, beside boering holes into the tree, it has a symbiotic relationship with a fungus that is proving to be deadly.

"There are lots of different types of fungus - many of them attack trees, but the trees are often able to respond and fight them off, similarly to the way a human  immune system fights off infections. The problem with this particular fungus is that some species of trees don't seem to be able to resist it and the fungus spreads  through the tree and kills the tree," he said.

Douwes said the fungus does not pose a threat to humans.

"I don't think fruit would be infected. The big concern is for fruit tree or timber farmers or anyone who is growing trees and may be susceptible to the fungus, is that
they could loose their crops and trees won't produce fruit to begin with," he said.

A tell-tale sign that a tree is infected is wood that is stained and presented with holes.

"The boere beetle makes tiny little holes from the stem in, about the diameter of a toothpick. On some trees, it's quite difficult to see that hole. Sometimes you willb be able to see fras, the sawdust pushed out by the beetle as it chews its way into the tree. But the most important thing is, if one were to cut the bark, they would see those tiny holes coupled with a dark vertical staining- that's a clear sign that the fungus is in the wood," said Douwes.

According to the Forestry and Agriculture Biotechnology Institute (FABI) the fungus has been found in on some backyard avocado's in Sandton and Knysna.

"Other fruit trees in private gardens on which it has been found include lemon, orange, guava, peach, and grapevine. However, at this point there is no evidence suggesting that (the fungus) poses a threat to these crops, but producers should carefully monitor and report any infestations," read the site.

In the commercial sector, oak and pine trees are at highest risk.

Residents who notice these signs are urged to report it to FABI as researchers are trying to track and understand the spread of the fungus. Call 012 420-3937 or 3938 or email: admin@fabi.up.ac.za

Source: Northglen News

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