Alternative Copper Fungicides for Blister Blight Management

Copper fungicides such as copper hydroxide, copper oxychloride and copper oxide of 50% or 37.5% w/w metallic copper are currently recommended for Sri Lankan tea plantations to manage blister blight. The recommended forms of these fungicides are either wettable powder (WP) or wettable granule (WG) formulations. Even though these fungicides are effective in blister blight management, due to environmental and health concerns of Cu, there is a growing demand for fungicides with reduced Cu contents. In the present study, suspension concentrate (SC) formulation of two copper fungicides with reduced Cu contents, copper oxychloride-copper hydroxide mixture (20% w/w metallic Copper) (Airone) and tribasic copper sulphate (26.95% w/w metallic Copper) (Cuproxat), were tested for their field efficacy to manage blister blight of tea. Copper oxychloride- copper hydroxide mixture treatments at 0.12 - 0.16 % and tribasic copper sulphate treatment at 0.5% gave blister blight control comparable to 50 % w/w copper oxychloride treatment. The Maximum Residue Limit (MRL) for copper (40 ppm) in made tea set by European Union (EU) could be achieved 7-day after spraying when copper oxychloride-copper hydroxide mixture and tribasic copper sulphate sprayed at 0.12 - 0.14% and 0.5%, respectively. Cost of copper oxychloride-copper hydroxide mixture is comparable to that of the recommended 50% w/w copper oxychloride WP. However, cost of tribasic copper sulphate is considerably higher compared to the control. Copper oxychloride-copper hydroxide mixture and tribasic copper sulphate suspension concentrates are dust free formulations and readily dissolve in water. Therefore, the new fungicides would be potential alternatives to the recommended copper fungicides to ensure user and environmental safety.