The guava industry in South Africa was established in the Western Cape Province in the early 1900s and in the Limpopo and Mpumalanga Provinces in 1938. Guava orchards cover almost 1200 ha in South Africa with 547, 442 and 140 ha respectively in the areas above. The total production per annum is approximately 41,000 tons. The bulk of this (31,000 tons) is processed while 10,000 tons is sold in the formal fresh market. The guava export market amounts 20% and constitutes mainly guava puree and pulp. Since 1981 guava wilt disease (GWD), caused by Nalanthamala psidii, has been a serious disease in most guava-producing areas of the Mpumalanga and Limpopo Provinces of South Africa. Control measures other than eradication of diseased trees do not exist. Two resistant rootstocks 'TS-G1' and 'TS-G2' were developed by the Agricultural Research Council's Institute for Tropical and Subtropical Crops (ARC-ITSC) by 1995, and Plant Breeders Rights were granted to 'TS-G2' in 2000. These rootstocks were developed by screening 30,000 guava seedlings in vitro using cell free filtrates derived from N. Psidii. The release of the 'TS-G2' rootstock by the ARC made it possible for the industry to re-establish guavas in areas affected with GWD and saved the guava industry in Mpumalanga and Limpopo from extinction. In 2009, a second outbreak of GWD was reported from several localities, which also affected the resistant 'TS-G2' cultivar, placing the guava industry under threat once again. Measures currently undertaken to address this new threat include screening of chemical and biological products against the GWD isolates as short term solution as well as further in vitro screening of thousands of seed for a long term solution. This paper gives an overview of guava wilt disease in South Africa and aspects included are, symptomatology, taxonomy of the pathogen, epidemiology, screening for resistance and management practices.
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