Bugs launched to halt alien invaders

RESEARCHERS yesterday released several small Brazilian bugs into the wild, marking the start of a campaign to halt the spread of an alien invasive plant infesting large areas of South Africa's north-east coast.

Known to entomologists as Catorhintha schaffneri, the yellowish-brown insect, about half the size of a human thumb, feeds on Pereskia aculeata - or Barbados gooseberry - a type of cactus indigenous to South and Central America.

Pereskia was brought into South Africa a century-and-a-half ago. The fast-growing invasive plant now infests large areas of the warm subtropical coastal region between Port St Johns and Mozambique.

Which is why Rhodes University lead researcher Dr Iain Paterson has been studying the Brazilian bugs for the past seven years — and rearing them in large numbers since 2012 —after receiving permission to do so from the agriculture, forestry and fisheries department.
Yesterday, Paterson released some of them for the first time, with official approval, on the campus. He said the small creatures —which he has dubbed stem-wilters —feed exclusively on the growing tips of pereskia plants, stunting their growth and reducing their ability to compete with other plants.

He described the bugs as the "perfect biological control agent", because they have no interest in any indigenous plant or crop.

"It is now clear that the pereskia stem-wilter can survive only on pereskia, and will die if it is forced to feed on any other plant."

Pereskia is a spiny vine with slender branches and pretty creamcoloured flowers. But it kills indigenous plants, including large forest trees, by climbing up and smothering them, to the extent that they collapse under the invader's weight.

It grows in ecologically sensitive and difficult-to-access areas, making it hard to control through herbicides and physical removal.

Paterson said efforts were underway to "mass-rear" stem-wilter bugs. The next step would be to release about 500 stem-wilter eggs at "as many sites as possible" across the pereskia-infested region.

Article Source: Pretoria News Weekend

Source:  Pretoria News Weekend

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