Singapore has over 50 leafy vegetable farms supplying the domestic market. More than 80% of the leafy Brassica vegetables produced are derived from covered land based soil cultivation i.e convention farms. To boost local production in land scarce Singapore, the Government has encouraged the use of technology and intensified land use. There are now several vertical farms producing vegetables outdoor and indoor in Singapore with or without soil. However, with intensified farming, plant pests are likely still a problem and impact may be more visible.
Fusarium oxysporum has been reported to be the causal agent for Fusarium yellows in soil based grown local leafy vegetables in Singapore. The local prevalence as determined in a 2010 - 2011 survey was about 64.2% (of a total of 246 samples). F. oxysporum and F. commune have been reported to be indistinguishable morphologically. In the same study, F. oxysporum was found likely to be F. commune when a sample size of 35 F. oxysporum isolates were further tested with specific primers. The local farms have been able to manage the Fusarium yellows disease with integrated measures and technical advisory from the government extension service.
Recently, a vertical farm in Singapore reported a yield loss of about 40-50% in the production of leafy Brassica vegetables and investigation of the production system revealed the involvement of two isolates of Fusarium i.e. F. commune isolated from diseased vegetables and soil and F. oxysporum isolated from irrigation water using sequencing. Morphologically, the Fusarium isolates appeared to be different from the isolates from the conventional farms. Koch’s postulates confirmed the Fusarium commune isolated from the diseased vegetables and soil as the pathogen.