Fungus threatens to wipe out jacarandas

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Trees in some parts of the city are at different stages of disease as branches fall off and leaves dry out. Picture: Masi Losi

Pretoria - Pretoria faces a future without its famed jacaranda trees, as a deadly fungus, which has been eating away at their roots for some time now, slowly attacks them.

Trees in some parts of the city are already at different stages of the disease, as branches fall off and leaves dry out.

“They are sick, and… we are facing a possibility of a city without jacarandas, but probably not in our lifetime,” says University of Pretoria biotechnology expert Professor Mike Wingfield.

Wingfield, director of the Forestry and Agricultural Biotechnology Institute at the university, said the root disease was caused by a fungus suspected to be native to the city.

It is thought the fungus originated from the roots of other trees.

“It’s moving quite slowly and it could take a while to wipe them all out, but then there is also always the possibility that some other disease could come in and wipe them all out quickly – that is what has happened with many other street and garden trees in other parts of the world,” Wingfield said.

Pretoria is renowned for its jacaranda trees, which turn the streets into a riot of purple blooms for about two months at the start of spring.

For about eight weeks purple flowers line the streets of the inner city and suburbs, as well as parks across the city.

Many conferencegoers plan their trips for October and tour buses drive through streets not normally on their routes so tourists can take pictures of the jacarandas.

There is an estimated 60 000 to 70 000 trees in the city.

They were introduced to the city in about 1888 from South America.

Referring to a controversy that surrounds the trees, Wingfield said they were declared a noxious weed, and there were “even suggestions by some groups that they should be cut down”.

They are considered an invader plant, and, according to the website gopretoria.co.za, since the tree is exotic, it is considered to be an invader plant, therefore no new trees are allowed to be planted. Recently, laws were passed that allow existing trees to be kept, but they may not be replaced when they die.

Wingfield disagrees with this policy and believes that they should be replanted in the city where they should remain a national heritage.

“They are, however, unable to protect themselves when they fall under threat from disease,” he said, adding that diseases were known to be able to wipe out entire forests.

He spoke from his home in Brooklyn, where he has a variety of trees, and where the streets outside are lined with jacaranda trees.

Outside his own gate is a huge jacaranda tree, on which he showed a team from the Pretoria News signs of a fungus, which he said was the beginning of the end for the tree.

The scientist, who has a special interest in the origin and patterns of global movement of insect pests and pathogens of trees, also pointed out branches affected by the disease, which had gone dry and whose leaves are falling off.

“This tree will be dead in four to five years, perhaps sooner,” he said.

Other trees in his neighbourhood have also started drying up, some barely shadows of their former selves, as they stood with no flowers, and broken branches.

“The branches sometimes break and fall off as the roots become diseased,” he said.

This has been going on for a while in the city, he said.

When the trees sensed that they were dying they rushed to produce seeds in an effort to reproduce before they die.

Wingfield said because trees lived for such a long time, their deaths, sometimes after a century or more of growth, was “tragic”.

“Trees make you happy, they make the environment beautiful,” he said.

Residents of the city should be grateful that someone had the good sense to plant seeds along the streets of the city, Wingfield said.

The jacaranda tree is listed as “vulnerable” on the International Union for the Conservation of Nature and Natural Resources’ Red Data list. - Pretoria News

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