The scale insect Aulacaspis yasumatsui is native to Southeast Asia and a major pest of cycad (Cycadales) plants. Due to an increase in worldwide trading of cycads, A. yasumatsui has spread globally and has become a major threat to many cultivated and native cycads worldwide. In this study we report formally, for the first time, A. yasumatsui infesting cycads in South Africa. This scale insect was observed infesting cycads in three provinces in South Africa, namely, Gauteng, KwaZulu-Natal and Limpopo. Its identification was based on morphology and nucleotide sequences of three gene regions. Although more common and damaging on non-native Cycas species, its presence on some native South African Encephalartos species is of concern and effort should be made to control the spread and impact of this pest in the country.
South Africa holds the greatest diversity of Encephalartos species globally. 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. Plant material with symptoms 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.
The cycad genus, Encephalartos, is endemic to Africa with more than half of its species occurring in South Africa. Seventy-three percent of South African Encephalartos species are threatened with extinction with four species already extinct in the wild. The major threat to Encephalartos species in South Africa is the illegal trade of cycads. In addition, biotic factors, such as insect pests and microbial diseases that affect these plants, are on the increase. The aim of this study was to identify diseases and insect pests of Encephalartos species in South Africa. Symptomatic plant material and insects were collected from diseased cycad species in the KwaZulu-Natal, Limpopo and Gauteng provinces. Microbial isolates obtained were identified based on morphology and DNA sequence data. Species of Alternaria, Phoma and Pseudocercospora were often isolated from leaf spots and Bionectria and Fusarium species from dying cycads. The plant pathogen, Phytophthora cinnamomi, was isolated from dying Encephalartos tranvenosus plants in the Modjadji cycad reserve in Limpopo. Insect pests observed causing the most damage to cultivated cycads were the beetle, Amorphocerus talpa, and the scale insect, Aspidiotus capensis. A. talpa was observed infesting cycad cones in the Pretoria Botanical Gardens, causing discolouration and death of the cones. The scale insect, A. capensis, was found on the leaflets of many cycads, causing chlorosis and premature death of leaves. In this study we also report, for the first time, the scale insect, Aulacaspis yasumatsui, infesting cycads in South Africa. A. yasumatsui was identified based on morphology and DNA sequence data. Plants infested by this scale insect showed symptoms of severe leaf chlorosis and necrosis. The presence of A. yasumatsui on South African Encephalartos species is of much concern and efforts should be made to manage this pest in the country.
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