Plant Destroyers Poster

The Cape Town Hypothesis Test

The Cape Town Hypothesis Test is an opportunity for you to contribute to important research.

Together we can conduct research to help protect the natural environment surrounding the mother city. Your contributions can lead to new discoveries and provide important information critical to conserving South Africa’s biodiversity and natural resources. Join us to release your inner scientist and conduct The Cape Town Hypothesis Test as a Biodiversity Protector.

The short

The natural environment surrounding Cape Town is important to protect and conserve. For example, Table Mountain is so special it has been declared a Natural World Heritage Site. One major threat to this environment is invasive microscopic organisms, particularly species that kill plants, such as the species in the group Phytophthora (Greek word: ‘plant destroyers’). Unfortunately, we accidentally move these plant destroyers around the world and introduce them to new areas and environments. Because of the role of people, we expect to find plant destroyers in the Cape Town area that have not yet ‘escaped’ into the natural environment (e.g. Table Mountain National Park). Therefore, we are asking you to particpate as Biodiversity Protectors, helping test this hypothesis and discovering these species before they are spread.


Cape Town is an incredible city because of the surrounding natural environment. The amount of tourism we receive because of its beauty alone is enough to economically justify our efforts to conserve these areas. The natural areas surrounding Cape Town are part of Cape Floristic Region, which has been described as the ‘hottest’ biodiversity hotspot in the world. Therefore, these areas are incredibly special and important to take care of. 

Microscopic organisms affect the world more than we tend to realize. Although we cannot see them without microscopes, microbes have helped shape the natural environment into what it is today. For example, the plants in the fynbos have evolved in a natural balance with the microbes present; some of these microscopic organisms help plants collect nutrients and water, where others recycle weak and dead plants. Therefore, understanding these relationships is important for protecting the natural environment.

Together we can advance knowledge and make the most of the world around us.

One major threat to the natural environment surrounding Cape Town is invasive species, including microscopic organisms. Yes, microbes can be invasive! Unfortunately, people accidentally move microbes around the world when they travel or buy goods from overseas (e.g. ornamental plants). Of particular concern to the fynbos are the microbes that cause plant disease (also known as ‘plant pathogens’). Accidentally introducing these microbes to new environments can start plant disease epidemics.

Examples of plant disease epidemics

Dutch Elm DiseaseChestnut BlightMyrtle Rust
Image Source: LinkImage Source: LinkImage Source: Link
One group of microscopic organisms that we are particularly concerned about is the group called Phytophthora, a Greek word that translates as ‘plant destroyer’. There are many species in this group, but not much is known about their diversity or distribution in the Cape Town area. These plant destroyers cause many plant disease epidemics around the world and threaten the biodiversity in the Cape Floristic Region.

Examples of Phytophthora plant disease epidemics

Protea Root Rot'Phytophthora' DiebackKauri Dieback
South AfricaAustraliaNew Zealand
Image Source: Joey Hulbert, FABIImage Source: Trudy Paap, FABIImage Source: Link


A hypothesis is an idea or question that is tested scientifically.

We hypothesize that together we will find different Phytophthora species in urban areas within Cape Town than we will find on Table Mountain, our Natural World Heritage Site.


Studying Phytophthora species in the urban areas of Cape Town is our best chance to detect the new arrival of an invasive Phytophthora species before it spreads into the natural environment.

Be a Biodiversity Protector

We are asking you to participate as citizen scientists in The Cape Town Hypothesis Test because you will be the first to notice the declines in health of plants in your neighborhoods and daily routines. You also have access to areas that we do not, such as your own backyard. You are more than welcome to submit samples from your own backyard if you notice an unhealthy plant.


Finding Phytophthora species

Phytophthora species can be recovered from soil if they are present. Therefore, we are asking you to collect soil and fine roots underneath unhealthy plants in your neighborhood. Easy directions for collecting soil samples can be found below.

Identifying sick plants

Because we are focusing on plant destroyers, we want to target sick plants. Below are a few images and descriptions of symptoms of pathogen infection to look out for.

Foliar DiebackStem Lesions & BleedsLeaf Lesions & Shoot Tip Dieback

Sample collection locations

We encourage you to collect samples from ANYWHERE in the urban areas of Cape Town and the surrounding communities (even from your own backyard), but we have circled a few very important areas in the map below. Once a sample is submitted from one of the circled areas, we will change the color to indicate that it has been sampled and add a GPS point with your name (if you would like). We only ask you to fill out the below webform so that we have the basic information (GPS/address information & nearby plants). We will then test whether there is a Phytophthora species present in the sample that you collected.

Please note, we ask that you do not collect samples in Table Mountain National Park or the other nature reserves because these areas require specific research permits, but we will do the sampling in these areas.

Sample Collection

1) Travel to one of the areas circled above.

2) Search for a sick looking plant.

3) Collect soil and fine roots from 2-3 locations underneath the plant.

4) Record GPS coordinates or the address, record the nearby plants and take a photo.

5) Clean or sterilize your spade or tools.
(Brush or spray tools with diluted rubbing alcohol, methylated spirts, soapy water, or bleach).

6) Fill in the below webform and submit the sample.

Submitting the sample

Samples can be sent or delivered to us in our lab at Stellenbosch University at the address below. We will also make monthly trips to the Cape Town area to arrange collections and share the project.

Joey Hulbert
Department of Conservation Ecology and Entomology,
University of Stellenbosch,
Private bag X1
Matieland 7602, South Africa

Submit a Sample for The Cape Town Hypothesis Test

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