Removal of Old Leaves and Soil Touching Unproductive Branches of Tea Bushes for Controlling Red Rust Disease in Bangladesh.

Abstract

Only leaf reduction (Cultural measure), in treatment T4 [treated with leaf removal above 15 inches (38.10 cm) from ground level], maximum yield (2185.00 kgha-1) was found resulted 21.64% more over the control. T3 [10 inches (25.40 cm)] and T5 [20 inches (50.80 cm)] gave similar response having 20 and 20.68% increased yield over the control. The lowest severity (21.38 PDI) was found in T5 [20 inches (50.80 cm)] that was statistically identical to T4 [15 inches (38.10 cm)] and T3 [10 inches (25.40 cm)] having a decrease trend of 58.28%, 50.26% and 42.59% respectively. There is 92.99% impact of leaf reduction in reducing disease severity of red rust having a decrease trend of 7.2 PDI for removal of leaf by 5 inches (12.70 cm) from the soil level. Similarly there is 81.44% impact of leaf reduction in increasing yield of made tea (kg ha-1) having an increase trend of 103.01 unit for removal of leaf by 5 inches (12.70 cm) from the soil level. In leaf reduction (Cultural measure) with one round chemical application, treatment T13 [treated with leaf removal above 15 inches (38.10 cm) from ground level with one round of Carbendazim 50 WP] gave maximum yield (2,310.00 kgha-1) resulted 28.61% more over the control followed by T15 [20 inches (50.80 cm) with one round of Carbendazim 50 WP] and T14 [20 inches (50.80 cm) with one round of Copper-oxichloride 50 WP] having 28.18 and 27.69% increased yield of made tea.  Lowest severity (9.63 PDI) was found in T15 [20 inches (50.80 cm) with one round of Carbendazim 50 WP] having 41.21% reduction over control followed by identical PDI in T12 [15 inches (38.10 cm) with one round of Copper-oxichloride 50 WP], T13 [15 inches (38.10 cm) with one round of Carbendazim 50 WP] and T14 [20 inches (50.80 cm) with one round of Copper-oxichloride 50 WP] having 77.40, 77.31 and 77.79% reduction respectively. There is 78.24% impact in reducing disease severity of red rust having a decrease trend of 2.23 PDI for removal of leaf by 5 inches (12.70 cm) from the soil level with one round chemical fungicide application. Similarly there is 51.76% impact in increasing yield of made tea (kg ha-1) having an increase trend of 30.21 unit for removal of leaf by 5 inches (12.70 cm) from the soil level with one round chemical fungicide. From the benefit cost analysis it is projected that the treatment T3 [10 inches (25.40 cm)] received the highest marginal rate of return (1202.17%) followed by 1152.17% in treatment T4 [treated with leaf removal above 15 inches (38.10 cm). One round of systemic fungicides like Carbendazim 50 WP with this cultural practice gave 1034.21% and 1091.42% marginal rate of return respectively. Considering yield of made tea, disease severity and benefit cost analysis viewpoint, it can be concluded that, the cost effective treatment is removal of soil touching old leaves attached with tea bushes of MSK and LSK pruned sections within 10 inches (25.40 cm) to 15 inches (38.10 cm) from the soil level.