Article and photos by Joey Hulbert
PhD Student, Forestry and Agricultural Biotechnology Institute,
University of Pretoria
P
lant diseases challenge the
sustainability of many agricultural productions. Millions of Rands are spent
each year in control efforts (e.g.
fungicide applications), while even
more are lost in damages from various plant diseases. Disease is a term
generally associated with the symptoms of infection from a pathogen—microorganism that causes
disease. One group of plant pathogens that cause disease in agricultural systems throughout South
Africa is Phytophthora. The name of
this group, Phytophthora— translated from Greek as ‘plant destroyer’— was coined by Anton de Bary
in 1876 when he identified and described the cause of potato late
blight, Phytophthora infestans.
estimated to be undiscovered.
Phytophthora infestans is possibly
Phytophthora species affect many
the most well-known species of
Phytophthora because it is responsible for the Irish potato famine.
More than a century after the discovery of this microbe, it still challenges the sustainability of many
potato and tomato productions
today, and the actual origin of this
species is still under debate. When
thinking about the impact this individual species has had on history
(i.e. the displacement of a large
proportion of the Irish population
as a result of compromised food
security and starvation), it is concerning to know there are now
close to 140 described species of
Phytophthora, with hundreds more
different agricultural systems in
South Africa, from plantation forestry to the cut flower industry, including many vegetable and fruit
growers; in general, the sustainability of each of these agricultural systems is challenged by a different
species of Phytophthora, depending
on the plant species involved. For
example, citrus growers are not affected by P. infestans, but rather,
species such as P. nicotianae or P.
citrophthora. However, one species,
Phytophthora cinnamomi (a root
rot pathogen first described killing
cinnamon trees), is ubiquitous in
agricultural and natural systems
throughout South Africa. This indi-
Citizen Scientist attempting to isolate Phytophthora
Citizen Scientist exposing Phytophthora canker