Joey Hulbert is a student on a mission to keep Table Mountain clean – of miniature plant-killing organisms from foreign lands, that is. To do so, he first needs to know which ones are already in Cape Town’s suburbs and nature areas, and if there are any among these to be concerned about. Therefore, he is asking Cape Town’s residents to look in their gardens and neighbourhoods for dying plants, and to send him some soil samples.
Hulbert is working towards a PhD in plant pathology through the University of Pretoria. He is based at Stellenbosch University as a research affiliate because he is compiling an inventory of the types of Phytophthora species found in the Cape fynbos. These include organisms found naturally in the area, as well as those that have been introduced to the region from other parts of the world.
“Phytophthora generally means ‘plant destroyers’ in Greek,” he explains. “Species in this group of microscopic organisms are known to infect and kill plants.”
Hulbert points out that these are not harmful to people and that not all micro-organisms are harmful to plants. Many have helped to shape the natural environment into what it is today.
“Examples like mycorrhizae and nitrogen-fixing bacteria help plants to collect water and nutrients, while others help to recycle dead plants into compost,” he explains. “Fynbos plants, for instance have, over millennia, evolved a natural partnership or balance with the microbes that are naturally found in the Cape Floral Region.”
However, when organisms are introduced from elsewhere in the world, the natural playing fields get scrambled.
Hulbert’s Cape Town Hypothesis Test
His research has already taken him to the Stellenbosch Mountains, Chapman’s Peak, and Cape Point, among others. Now his sights are on Cape Town, and Table Mountain in particular, to discover the tally of naturally occurring and introduced Phytophthora species.
“My best guess or hypothesis based on findings in other parts of the world is that there might be a few species in Cape Town’s home gardens and on street trees that have been introduced from elsewhere,” Hulbert says. “If we know what these are, we can compare what we find to the tally of species currently occurring on Table Mountain.”
Hulbert is holding thumbs that the research will reveal that Table Mountain is still “clean” when it comes to invasive or foreign Phytophthora species.
“We know of one species, Phytophthora cinnamomi, that has been introduced from south east Asia to South Africa and Table Mountain, but this may have happened some 300 years ago,” says Hulbert. “The important part is, however, to keep it as such, because it is a Natural World Heritage Site and home to many distinctive plant species found nowhere else in the world.”
Phytophthora cinnamomi is known to have infected more than 80 indigenous plant species, five of which are critically endangered.
“While we suspect this species has been around for hundreds of years in South Africa, we do not have a strong understanding of the impacts it has had, and we are concerned about the introduction of similar species to the rest of the Cape Floral Kingdom,” says Hulbert.
What happens if he finds potentially worrying species in the suburbs? “Such information will definitely be shared with the management staff of the Table Mountain cable car and SANParks, so that they could consider including basic sanitation methods into their tourism management structures,” he says. “It might in any case be well worth considering including basic steps such as asking tourists to clean dirt off the soles of their shoes before they head up the mountain, or to have visitors walk over disinfectant mats while they are waiting for the cable car.”
“The species we are talking about are very small, and their spores can actually only be seen under the microscope,” Hulbert explains. “They can accumulate in soil that gets collected on your shoes or equipment in one place, and then spread elsewhere.”
Areas of particular interest
“The more ‘scientific’ eyes looking, the better chance we have of detecting a newly introduced invasive microbe before it can cause too much damage,” says Hulbert.
He is therefore calling on Capetonians to help him collect soil and plant samples of dying plants from anywhere in the urban area around Table Mountain. Of particular interest to his work is Hout Bay, Claremont, Green Point, Grassy Park, Ottery, Wynberg and Rondebosch, because some of these areas are close to the Cape Town harbour, while others have not yet been surveyed. Specific permits are required to sample in the national park itself so citizens are asked to leave those areas to Hulbert and park staff.
Hulbert will then analyse the samples in the laboratory at Stellenbosch University to see if there are any traces of disease-causing Phytophthora species.
He admits that it is difficult to decide whether a plant is dying because of a lack of water, or because of disease.
“Phytophthora most often attacks and kills a plant at its roots. The visible symptoms of this are very much the same as is caused by a lack of water,” explains Hulbert. “The best way to find out what is actually happening is to take samples from the soil and fine roots under the plant and to test these in the lab.”
“This way, we won’t miss a new introduction of a disease-carrying microbe by assuming the plants are killed by drought,” he adds. “Now more than ever, it is important to understand which microbes are affecting our plants, because when plants become stressed by drought, they will likely be more susceptible.”
How can the public help?
- Look out for plants in your garden and neighbourhood that look sick or are dying. Symptoms include dead leaves, lesions or dead tissues on leaves or stems, and dieback of branches and shoot tips.
- Collect soil and fine roots from about three spots around and underneath the plant. Avoid letting the sample get too cold or too warm.
- Record the GPS coordinates or the address of the site.
- Take a photo of the plant.
- If possible, remember to record the nearby plants, especially if any others look sick too.
- Clean or sterilise your spade or tools before and after use, to avoid contamination of samples or the accidental release of species from one area into another. Brush or spray tools with diluted rubbing alcohol, methylated spirts, soapy water or bleach.
- Fill in the webform available on citsci.co.za/capetown . Hulbert will organise the pick-up of the samples.
- For further information about the Cape Town Hypothesis Test, visit citsci.co.za/capetown or contact Hulbert via email@example.com or www.facebook.com/capecitsci. –Stellenbosch University