Clavibacter michiganensis subsp. insidiosus no longer occurs in South Africa
In South Africa, Clavibacter michiganensis subsp. insidiosus (bacterial wilt of lucerne - EPPO A2 List) was first reported in 1967 in a few regions (Western Cape, Eastern Cape provinces). In 1983, the bacterium was also reported in the Transvaal region, however this last record is now considered doubtful. Since then, no bacterial wilt symptoms have been observed on lucerne (Medicago sativa) crops and no official reports have been made in South Africa. In order to determine the current status of C. michiganensis subsp. insidiosus, field inspections and testing of seed lots were carried out in South Africa. Field inspections of lucerne seed crops were conducted in all producing regions from 2006 to 2014 and did not reveal any symptomatic lucerne plants. 67 representative commercial seed lots were tested and all results were negative. In addition, plant disease diagnostic laboratories in South Africa were consulted and confirmed that they have not identified this bacterium over the past 10 years. It is therefore concluded that C. michiganensis subsp. insidiosus is currently absent from South Africa.
The situation of Clavibacter michiganensis subsp. insidiosus in South Africa can be described as follows: Absent, pest no longer present.
Sources
Coertze S, Jensen T, Kotzé TN, McLeod A (2015) Establishing the status of Clavibacter michiganensis subsp. insidiosus in lucerne in South Africa. Journal of Plant Pathology 97(2), 283-290.
Thompson AH (1985) Technical Communication - Department of Agriculture and Water Supply, Republic of South Africa No. 197, 26 pp.
Van der Merwe SP, Du Toit JJ (1970) First identification of bacterial wilt on lucerne in the Republic of South Africa. Phytophylactica 1, 61-62.