Assessment of leaf spot disease on water leaf (Talinum triangulare (jacq.) Willd and in vitro effect of three medicinal plant extracts on pathogen(s) in the Northwest Region of Cameroon

Cultivation of waterleaf improves the life quality of families and provides additional income for farmers. However, waterleaf production in Cameroon has suffered a major blow from leaf spot disease. Ten farms with dimensions of 4 m by 3 m each in Nkwen, Bamenda, Cameroon were surveyed for leaf spot disease of Talinum triangulare. Disease incidence and severity were assessed by surveying the farms after every fourteen days for three months. Small pieces of infected leaf parts were inoculated on prepared plates of potato dextrose agar. After 7 days of incubation, pure cultures were made, and isolated fungi were identified according to recommended references. Aqueous extracts from Moringa oleifera (Leaves), Ocimum gratissimum (Leaves) and Zingiber officinale (Rhizomes) were evaluated for in vitro antifungal activities on Alternaria and Cercospora. Data collected for disease incidence and severity showed varying intensities at the different locations. Two fungi species were isolated from the diseased leaf samples collected from 5 farms and were identified as Alternaria spp. and Cercospora spp. All the extracts had inhibitory activities on the test fungi with the highest inhibition (79.6%) obtained from Zingiber officinale (Rhizomes) extract and the lowest inhibition (4%) obtained from Ocimum gratissimum extract.