Johannesburg - Mites so small you could fit a hundred of them on a pinhead are helping halt the spread of a highly invasive weed choking the life out of large tracts of South Africa’s countryside.
Dubbed “one of the world’s worst” invasive plants, lantana weed, or Lantana camara as it is known to botanists, has infested thousands of hectares of land in several provinces.
The rapidly spreading shrub, which sports a pretty, multi-coloured flower through the summer months, but has berries that are poisonous to cattle, forms impenetrable prickly thickets that exclude other indigenous plants.
But a microscopic gall mite, introduced as a biological control by the Agricultural Research Council (ARC), with the help of funding from the Working for Water project, is starting to halt its march along the country’s fence lines, woods, and water courses.
In its 2012/13 annual report, tabled at Parliament, the council says Aceria lantanae, a species of mite that is host-specific to lantana weed, are successfully munching their way through the weed’s flowers, so stopping it producing seeds.
“In 2011, researchers released the mite into affected sites in Limpopo, Mpumalanga, Gauteng and KwaZulu-Natal. At some release sites… the mite has significantly reduced flowering by up to 90 percent.”
According to the report, the tiny mite “has the potential to reduce the spread of lantana and reduce the loss of natural pastures and biodiversity, as well as the costs associated with mechanical and chemical control of lantana weed”.
According to the ARC’s website, lantana weed “comprises a complex of vigorous, prolific, man-made hybrids, bred in Europe from unrecorded parents from central and South America, and spread all over the world as a hardy, ornamental shrub”.
It arrived in South Africa in the 1960s, and, despite numerous attempts at biological control, remained one of the most vigorously growing, invasive weed species in the country.
The council says lantana weed has become “a serious ecological and economic burden” around the country.
Its seeds are dispersed by fruit-eating birds.
According to the report, the Aceria mite was introduced after it was found to pose no threat to any economic or indigenous African plant.
It destroys lantana weed by feeding on the plant’s flower buds, which induces the formation of a gall, an abnormal outgrowth in plant tissue, rather than a flower head, thus reducing seed production.
“The mites also proved quite resilient, surviving in more areas than initially expected, as demonstrated by its survival during winter in sheltered spots around the Pretoria release sites.” - Sapa