Press release
Ragweed pollen –
a
highly allergenic weed native to North America – was detected in South
African pollen spore traps for the very first time. Eradicating this
invasive weed
is critical as its fine pollen is highly allergenic and it also poses a
threat to crop health. If you find a ragweed bush near your home, pull
it out as it is incredibly invasive. Due to the changing climate,
ragweed will continue its migration southward putting
more South Africans at risk of developing a sensitivity to its potent
pollen.
This
week scientists made a landmark discovery when ragweed – a highly
allergenic weed native to North America – was detected in South African
pollen spore
traps for the very first time.
The
discovery was made by Dr Dilys Berman, an aerobiologist at UCT and Prof
Jonny Peter, who heads up the UCT Lung Institute’s Allergy Unit.
Palynologist,
Dr Frank Neumann, based at Wits University whose research focuses on
the impact that climate change has on vegetation, also confirmed that
the pollen grains indeed belong to the invasive Ambrosia species.
Prof Peter says while the
threat
of allergic plants, such as ragweed migrating southward, because of
climate change, has always been a concern, little did they know it was
going to show up so soon.
“Ragweed
is incredibly invasive, and its potent pollen has been problematic in
the US for many decades. In recent years, allergy sufferers
in Europe and South America have also come under threat as ragweed
started to invade these areas.
“For
now, KwaZulu-Natal residents are most at risk as ragweed pollen has
recently been detected at the Durban monitoring site over
the last few days. The counts are relatively low at this stage, but we
are monitoring
them daily
to detect any sudden spikes. A small
population of ragweed has also been found on the banks of the Vaal River
near Heidelberg – about 50km away from Johannesburg, while 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 says.
UCT aerobiologist, Dilys Berman warns that ragweed poses a serious implication for human health.
“It’s
been one of the most loathed weeds in the US, causing misery for 23
million Americans and it’s estimated that ragweed allergy rates in
Europe will
increase from 33 to 77 million in the next two decades. While we haven’t reported sensitisation in SA yet, it is a cause for concern.
“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, post-nasal drip etc, which could irritate
and restrict the airways making it difficult to breathe.
Prof
Peter points out that because of the world’s changing climate, ragweed
is projected to decline in some areas as it may over time no longer be
climatically
suitable to grow there.
“Either
way you look at it, ragweed is on the move. Once it sprouts, it can
multiply and grow up to 2 metres in height 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 that
ragweed poses a threat to crop health. It drains the soil and oppresses
plant growth, so is definitely a weed that should be kept an eye on and
monitored carefully,” he says.
Pollen monitoring in SA is funded by Clicks, Twinsaver,
Thermo Fischer,
A.Vogel Echinaforce, Zeiss and Durand.
The relevant pages on Agribook.Digital are "Invasive alien species" and "Crop protection".
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