In vitro evaluation of twelve fungicides against three major fungal pathogens of tropical tuber crops

Abstract

The productivity of tropical tuber crops is significantly threatened by a variety of diseases caused by fungi and viruses. These pathogens not only reduce yield but also affect the quality of the tubers, leading to substantial economic losses. Fungal pathogens, such as Sclerotium rolfsii, Colletotrichum gloeosporioides and oomycete, Phytophthora colocasiae are among the most destructive, causing diseases like collar rot in elephant foot yam, anthracnose in yam and taro leaf blight. Mancozeb is a broadly used fungicide for the control of plant diseases, including taro leaf blight and it has been banned for agricultural use by few countries due to its hazardous effects to humans and the environment. In a search for replacement of fungicides, twelve fungicides at different concentrations (100, 200, 400, 800 and 1600 ppm) were tested for their ability to arrest the major fungal pathogens of tropical tuber crops viz., Colletotrichum gloeosporioides, P.colocasiae and Sclerotium rolfsii. The chemicals recommended for the management of the diseases, mancozeb and carbendazim alone and their combinations with other chemicals were included to get the comparative efficiency of alternative options. The results suggest use of fungicides, difenoconazole, hexaconazole and metalaxyl-M+ chlorothalonil to manage diseases caused by Colletotrichum gloeosporioides. Metalaxyl-M+ chlorothalonil (Folio Gold) and cymoxanil+famoxadone (Equation Pro) can provide better protection from Phytophthora colocasiae. Hexaconazole and difenoconazole showed highest mycelial growth inhibition of S.rolfsii even at the lowest concentration tested. The lead obtained from the study will be a stepping stone to revisit the chemical management strategy followed to combat the pathogens.  Keywords : Fungicide, Sclerotium rolfsii, Colletotrichum gloeosporioides, Phytophthora colocasiae, Tuber crops