Pollen allergy warning as US ragweed is detected in SA for the first time
KwaZulu-Natal residents most at risk but weed also spotted in Heidelberg, 50km from Johannesburg
Ragweed, which is a highly allergenic weed native to North America, has been detected in South African pollen spore traps for the first time.
The discovery was made by Dr Dilys Berman, an aerobiologist at the University of Cape Town, and Prof Jonny Peter, who heads the UCT Lung Institute’s Allergy Unit. Palynologist Dr Frank Neumann, based at Wits University, also confirmed the pollen grains belong to the invasive Ambrosia species.
"While we haven’t reported sensitisation in SA yet, it is a cause for concern," said Berman.
"Increasing amounts of fine-powder ragweed in SA could exacerbate hay fever symptoms and asthma for the estimated 17-million South Africans who suffer from allergies.
"Given that its highly allergenic, people who normally don’t suffer from pollen allergies may develop a sensitivity to it in the future as the weed proliferates."
Common hay fever symptoms include red, itchy and watery eyes, a runny, itchy or congested nose and a post-nasal drip which could irritate and restrict the airways, making it difficult to breathe.
“For now, KwaZulu-Natal residents are most at risk as ragweed pollen has recently been detected at the Durban monitoring site over the past few days," said Peter.
"The counts are relatively low at this stage, but we are monitoring them daily to detect any sudden spikes."
The professor said a small population of ragweed had also been found on the banks of the Vaal River near Heidelberg, about 50km from Johannesburg.
The Eastern and Western Cape still remain ragweed-free.
“Based on historical data, ragweed thrives in hot, dry environments and produces more pollen when CO2 levels are high,” he said.
Once ragweed sprouts, it can multiply and grow up to 2m high in a matter of weeks.
“Weed control boards should add it to their invasive weeds list as soon as possible, if they haven’t done so already, and removal thereof should be a priority before it becomes impossible to control. Some studies also suggest ragweed poses a threat to crop health. It drains the soil and oppresses plant growth, so it is definitely a weed that should bemonitored carefully,” said Peter.