Improvement in the Management of Leaf Blight Disease of Taro (Colocasia esculenta) with Copper and Metalaxyl Fungicides

Abstract

Taro (Colocasia esculenta (L.) Schott) is an important staple food crop for millions of people in developing countries. Taro production is constrained by many diseases of which leaf blight, caused by Phytophthora colocasiae Raciborski, is the most destructive and it accounts for up to 80% yield loss of taro in many countries. In Ghana, the disease accounts for 25 – 50% yield loss. Non-sustainability of cultural control method and the use of resistant varieties have compelled some farmers to abandon their fields while others have converted their farms to dry season vegetable farming. In this study, copper and metalaxyl fungicides were tested for the control of leaf blight disease of taro. In vitro fungicidal activity tests and field evaluation showed that Ridomil Gold Plus 66 WP (6% metalaxyl-M + 60% copper (I) oxide) and Metalm 72 WP (12% metalaxyl + 60% copper (I) oxide) at 50 g in 15 litres of water (3.3g/L) and Nordox 75 WG (86% cuprous oxide) at 75 g in 15 litres of water (5 g/L) are effective for the control of leaf blight disease of taro at 4 weekly intervals for five consecutive months in the wet season.

Severity of Phytophthora leaf blight disease and susceptibility of two local varieties of Colocasia to Phytophthora colocasiae Raciborski in Nsukka zone of South Eastern Nigeria

“…The higher resistance portrayed by var. esculenta suggests that it may contain higher levels of disease resistant compounds like phenols and polygalacturonase inhibitors (Ugwuja and Chiejina, 2011;Omane et al, 2020). In addition, the severity of TLB is dependent on Phytophthora population (the amount of inoculum) in the field at the time of planting (Brooks, 2007) and host plants carrying partial (horizontal) resistance will probably become infected but the rate at which the disease develops depends on the environmental conditions (Agrios, 2005).…”

Taro in West Africa: Status, Challenges, and Opportunities

“…The disease thrives where day and night temperatures range between 25-28 • C and 20-22 • C, respectively, and can assume epidemic proportions all year round under favorable conditions [48]. TLB was not known in WA before 2009, when there were simultaneous outbreaks in Nigeria, Cameroon, Ghana, and other neighboring countries [20,21]. It is estimated that TLB in WA accounts for an economic loss of about USD 1.4 billion annually [19].…”

“…In WA, taro is reported to be present in all countries [9,12,17,18] except for Mauritania, where there is a paucity of information on its production. However, taro production in WA has been severely affected by the emergence of taro leaf blight (TLB), caused by Phytophthora colocasiae Raciborski [19][20][21]. Since its outbreak in WA, TLB has accounted for an economic loss of more than USD 1.4 billion annually, leading to the genetic erosion of the crop in this region [19].…”

Phytophthora Diseases Prevalence, Its Effects and Controls in Ghana

“…The production of taro in Ghana, in recent times, has been affected by the taro leaf blight caused by Phytophthora colocasiae which has also been reported to have threatened the sustainability of taro production globally [21,22]. In Ghana, [23] reported the presence of the disease after similar reports in Nigeria and Cameroon. The disease affects all parts of the crop including the leaves, corms, petioles and cormels, resulting in extensive damage of the foliage and reduced yield [24].…”