Abstract:
South Africa holds the greatest diversity of Encephalartos species globally. I In recent years
several reports have been received of Encephalartos species in the country dying of unknown
causes. The aim of this study was to investigate the presence of, and identify the causal agents of
diseases of Encephalartos species in the Gauteng and Limpopo Provinces of South Africa.
Symptomatic plant material and insects were collected from diseased plants in private gardens,
commercial nurseries and conservation areas in these regions. Insects collected were identified
based on morphology, and microbial isolates based on morphology and DNA sequence data.
Insect species identified infesting cultivated cycads included the beetle Amorphocerus talpa, and
the scale insects, Aonidiella aurantii, Aspidiotus capensis, Chrysomphalus aonidum, Lindingaspis
rossi, Pseudaulacaspis cockerelli, Pseudaulacaspis pentagona and Pseudococcus longispinus.
Fungal species isolated from diseased plants included species of Diaporthe, Epicoccum,
Fusarium, Lasiodiplodia, Neofusicoccum, Peyronellaea, Phoma, Pseudocercospora and Toxicocladosporium. The plant pathogen Phytophthora cinnamomi was identified from E.
transvenosus plants in the Modjadji Nature Reserve. Artificial inoculation studies fulfilled Koch‟s
postulates, strongly suggesting that P. cinnamomi is responsible for the deaths of these plants
under field conditions.
