Alien invasive castor oil plant hosts dangerous shot hole borer beetle in KZN

The alien invasive castor oil plant has taken root along the urban edge of the North Coast region and, unless contained, its effortless spreading poses a real threat to the environment, reports North Coast Courier.

Known as Ricinus communis in botanical circles, it is Cara Category Two alien invasive.

This means it is a plant with commercial or utility value that may only be grown with a permit under controlled circumstances in a demarcated area.

Like many other invasive species, it loves cleared road verges, where it is found in abundance.

ALSO READ: How to stop the voracious beetles killing SA’s trees

It is very adaptable to different environments and has been widely distributed by human activities.

However, the real danger this alien plant poses is that it serves as an ideal host to the deadly polyphagous shot hole borer (PSBH) beetle.

The beetle carries a fungus that rapidly kills trees.

According to Simbithi’s PSBH working group, the beetle originated from southeast Asia and is about the size of a sesame seed. It has been detected in every province except Limpopo.

Ballito was the seventh region in the country where it has been identified.

The symptoms of infestation differ across trees.

According to Simbithi’s Eco Estate landscape supervisor, Michael Riley, from the Simbithi PSBH working group, both indigenous and exotic trees in South Africa are affected and dying by the thousands because of the beetle that experts say is “impossible to eliminate”.

And while this happens, there is a race on to find the right chemical to treat infested trees.

“The major challenge with the beetle infestation is that the insect is crossing the boundaries between agriculture, commercial forestry, natural forests, and urban trees.

“Never in the country’s history has any insect attacked and killed trees in all these sectors,” said Riley.

The protection of trees in the different sectors is typically dealt with by different government departments and municipalities. But given the beetle’s unusual behaviour, routine action plans aren’t enough to curb the problem.

The spread of PSHB through invasive species increases the risk that it would spread to agricultural crops such as avocado and macadamia.

This is according to Jan-Hendrik Venter, manager of plant health early warning systems at the Department of Environmental Forestry and Fisheries.

Venter told the Courier the National Environmental Biodiversity Management Act provides for the management and conservation of South Africa’s biodiversity and has regulations in place that deals with alien invasive species.

Derrick Lilienfeld with the alien invasive castor oil plant that is spreading across the Dolphin Coast suburbs.

After arriving from Southeast Asia, presumably in wooden pallets on a ship, about four years ago, the PSHB has spread across South Africa.

Simbithi Eco-Estate’s landscaping department took the initiative to send samples off for testing after they began to suspect the feared beetle was infesting and killing trees on the coast.

Their fears proved to be true, after DNA sequencing by the Forestry and Agricultural Biotechnology Institute confirmed their presence.

The revelation has sparked serious concern in both the eco-estates and agricultural sectors, who stand to lose a lot if these invasive beetles are not dealt with swiftly and properly.

Derrick Lilienfeld, who is also on the Simbithi working group, said the castor oil plant, which is breeding prolifically in the area, is one of the major hosts to the PSHB.

An example of this is that from one 500-gram sample of castor oil plant stem over 119 adult PSHB beetles, 46 larvae and 89 pupae were recovered.

Despite such a heavy infestation, it seems the castor oil plant is not adversely affected and continues to grow.

“A mature castor oil plant can host thousands of beetles, and a new PSHB infestation can start from only one female beetle.

“It has been suggested that the castor oil plant could be a major source of the PSHB populations that are spreading to our regions indigenous forests and woodlands,” said Lilienfeld.

What can be done?

• If the alien invasive is on municipal property, contact KDM park and gardens department’s Che Gopi at 032 437 511/5113 or email cheg@kwadukuza.gov.za, sheilas@kwadukuza.gov.za

• If you suspect PSBH infestation, landscape contractor Darren Coull has set up a wood chipper in Foxhill where he can dispose of infected wood in the proper manner.

• If you suspect you may have an infestation of shot hole borers but are not certain, call Coull at 082 562 4446 for assistance.

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