Efficacy of hot water treatment in management of sugarcane ratoon stunting disease

Sugarcane ratoon stunting disease (RSD) caused by the bacterium Leifsonia xyli subsp. xyli causes huge losses to sugarcane ratoon crops. Hot water treatment is commonly used in many countries to control RSD but conflicting results show that it may have either positive or negative effects on yield based on variety, temperature and duration of therapy. Effect of hot water treatment in management of RSD was determined on three sugarcane varieties (CO421, D8484, KEN 83737) at 45°C, 50°C, 52°C and 55°C for two hours. Control cane was treated with cold water at room temperature at 25°C. The treated cane was planted in the field and data collected on cane girth, cane height, number of millable stalks, cane weight and sucrose content. Hot water treatment at 45°C, 50°C and 52°C significantly reduced RSD incidence and increased cane yield while treatment at 55°C completely eliminated RSD but significantly reduced cane yield. The cane setts which were treated with cold water at 25°C were stunted and had low overall cane yield. Hot water treatments at 50°C was the most effective and produced the highest cane yield followed closely by treatment at 52°C. Therefore the two temperatures are recommended for management of ratoon stunting disease of sugarcane. Treatment of sugarcane setts at high temperatures of 55°C for two hours though effective in reducing RSD is harmful through reduction in germination of setts and thus total plant population and eventually low cane yield.