Pesky weeds face extinction by insect

ONE of South Africa's "worst weeds" will soon meet its match and become the staple diet of an insect imported specifically to fight the alien plant.

Rhodes University's Dr Iain Paterson, lead researcher in the zoology and entomology department, has been working with the little insects known as stem-wilters since 2007 and believes they are ready to start rearing them on a large scale to target pereskia weeds.

The Department of Agriculture, Forestry and Fisheries (DAFF) recently granted permission to release the pereskia stem-wilter (Catorhintha schaffneri) in South Africa as a biological control agent to pereskia.

"After many years of research it is now clear the pereskia stem-wilter can only survive on pereskia and will die if it is forced to feed on any other plant."

This means if the pereskia stem-wilter is released it will ... not harm any indigenous plants or crops," Paterson said.

Pereskia (pereskia aculeata) is an invasive alien plant that was brought to South Africa in 1858 as a curiosity.

It destroys South African native biodiversity by smothering indigenous plants and killing large forest trees which collapse under the weight of the weed.

Pereskia grows in ecologically sensitive areas that are difficult to access.

This makes removing it difficult, both physically or with the use of poison.

It also reproduces very easily, and can grow from small fragments left behind when it is removed. Pereskia grows intertwined with indigenous plants so it cannot be removed without killing indigenous plants as well.

If all the pereskia in an area is destroyed the insects will either move to another site where pereskia grows, or they will die out, causing no damage to other plants. 

By Riaan Marais

Photo: Dr Iain Paterson

Source: The Herald

Source:  The Herald

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