Submitted to: Phytoprotection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/13/2009
Publication Date: 12/7/2009
Citation: Muchiri, F.N., Narla, R.D., Olanya, O.M., Nyankanga, R.O., Ariga, E.S. 2009. Efficacy of Fungicide Mixtures for Management of Phytophthora infestans (US-1) on Potato. Phytoprotection. 90:19-29. Interpretive Summary: Late blight is a devastating disease on potato and tomato. Different fungicide application strategies (timing, frequency, rates and combinations) have potential to enhance late blight disease control. We evaluated several fungicides when used alone and in various combinations for their ability to control potato late blight under different environments in Kenya. Late blight was considerably reduced by a combined mixture of fungicides compared to when those products were applied alone. Similarly, fungicide combinations increased tuber yield compared to untreated controls and to application of a single fungicide. This study showed that greater potato yield and better late blight disease control can be obtained by applying combinations of particular fungicides.
Technical Abstract: Fungicide application strategies (timing, frequency, rates and mixtures) are important for control and resistance management of late blight, caused by Phytophthora infestans. The efficacy of systemic/protectant fungicide consisting of fenamidone + mancozeb, and propamocarb–HCL + mancozeb combinations at various rates were evaluated for late blight control (US-1) on potato cultivar Kerr’s Pink relative to mancozeb, metalaxyl and an untreated control in a two year experiment at four potato growing areas of Kenya. Late blight was initiated from natural inoculum during the cropping seasons. Foliar blight severity was evaluated in field plots based on visual assessment. At harvest, total and marketable tuber yield were quantified. Propamocarb–HCL + Mancozeb, and Fenamidone + Mancozeb, significantly (P<0.05) reduced foliar blight compared to mancozeb and the check under moderate to severe disease pressure. Efficacy of fungicide combinations was comparable to metalaxyl for blight control. Disease levels varied among locations, and blight severity ranged from 5-67% in fungicide treated plots compared to 81-99% in untreated checks at Tigoni. At Molo, Kinangop and Mt. Kenya locations, late blight severity ranged from 5-18% and 85-95% in fungicide-treated and check plots; respectively. Total and marketable tuber yield significantly (P<0.05) increased in fungicide treated potato plots. This study demonstrates that fungicide mixtures or combinations can be effectively utilized to manage late blight as opposed to singular or sequential use of protectant or systemic fungicides, with concomitant increases in tuber yield.