Under the NEMBA Alien and Invasive Species Regulations, pompom weed is listed as a Category 1b invader in Gauteng, North West, Limpopo and Mpumalanga and Category 1a in the rest of South Africa, meaning that every effort must be made to remove and destroy it.
The distribution of pompom has almost doubled in the past five years. It threatens grasslands, open savanna and wetlands by decreasing the carrying capacity of the land. The plant is unpalatable to wildlife and agricultural livestock.
It also threatens indigenous herbs and grasses. It is almost impossible to control mechanically due to its robust root system and copious seed production. Herbicide application is expensive and labour intensive and therefore restricted to roadsides and smaller, manageable areas, so biocontrol is deemed to best long-term solution to control pompom weed.
On 23 October 2013, the thrips (Liothrips tractabilis) was released in Pretoria at Rietvlei Nature Reserve. Additional releases were made a month later at Swartkop Airforce Base and Rietondale (ARC-PPRI research farm) and Roodeplaat Nature Reserve. At the beginning of December 2013, releases were made at a further six sites around Pretoria.
Recruited from Argentina, where pompom weed is indigenous, the pompom thrips causes significant damage to the stems and leaf tissue at the growing tips. This causes deformities in plant growth, reducing the height, biomass and flower production of this unwanted weed.
A second promising biocontrol agent for pompom weed is the flower-feeding moth (Cochylis campuloclinium) which is still undergoing testing by scientists in quarantine facilities around the country.
How to control pompom weed on your property
Herbicides registered for use on pompom weed are Plenum, Access and Climax. The two physical methods include uprooting and burning of the plant. Herbicides must always be used in accordance with the manufacturer’s guidelines as well as national and provincial regulations.