Fusarium wilt was first observed on the farm Metocheria near Namialo in northern Mozambique in February 2013 following unusually heavy rains. The distribution pattern of the disease, however, suggested that the disease was present for longer. As the rain was preceded by severe drought spells during the previous year, it is possible that symptoms were mistaken for plants under severe drought stress. The mapping of new outbreaks, however, showed that Fusarium wilt was spreading rapidly, and could be found in most of the plantation blocks of Farm 2 (on six farms on Metocheria). The other arms, however, had only a few cases of diseased plants. After the discovery of the disease, samples were sent to scientists in Mozambique and South Africa, and the responsible fungus was eventually identified by scientists at Stellenbosch University in South Africa. The samples from diseased banana pseudostems collected at Metocheria Farms often contained both Fusarium species and bacteria. The identification of bacteria confirmed their role as secondary contaminants. The Fusarium strains, however, were identified morphologically as members of Fusarium oxysporum, and by pathogenicity testing as F. oxysporum f. sp. cubense (Foc), the banana Fusarium wilt pathogen. Two sets of molecular markers indicated that Foc isolates were members of vegetative compatibility group (VCG) 01213/16, better known as Foc 'tropical' race 4 (Foc TR4). Phylogenetic comparison to other VCGs of Foc also grouped the Mozambique strains into VCG 01213/16. The identity was confirmed by vegetative compatibility group (VCG) testing. The first Cavendish plantations at Metocheria Farms were established in 2009 with tissue culture banana plantlets obtained from DuRoi Laboratories (South Africa), and in 2011 more plantlets were obtained from Rahan (Israel). Six farms have been developed; each being managed independently. Metocheria Farms covers a total area of more than 16 000 ha, of which 1 500 ha have been planted to bananas. Each farms is approximately 250-300 ha in size, and none of them have distinctive borders. Farms 3 and 6 share a pack house, and so do farms 4 and 5. Farms 1 and 2 have their own packhouses. Soils have a high clay content and a pH (water) of between 6.0 and 7.5. Winter temperatures range from 15-25oC and summer temperatures between 30 and 45oC. Micro sprinkle irrigation is attained with water in two holding dams on the premises that are filled with water from the Monapo River. There was a considerable movement of people from local communities that walked through Metocheria Farms, and often through banana fields, until the discovery of Fusarium wilt. Also, farm personnel were rotated between fields, and international staff was replaced fairly regularly. The international staff includes experienced banana workers from other banana export countries such as Panama, Costa Rica, Honduras, Guatemala and The Philippines. Each of the farms had now been fenced in, and access to the premises is controlled at the main gate as well as between farms. |