Occurrence Of Sugarcane Ratoon Stunting Disease In Nyando Sugar Belt And Its Management By Hot Water Treatment
Sugarcane yield in Kenya has been on decline due to many factors including pests and diseases. Ratoon stunting disease (RSD) caused by Leifsonia xyli subsp. xyli is considered to be the most serious disease of sugarcane worldwide because it can cause up to 50% yield loss. This study was carried out with the objective of determining the prevalence and incidence of the RSD in Nyando sugar belt. Survey for the occurrence of RSD and sugarcane production practices was conducted from November, 2014 to February 2015 in three agro-ecological zones (AEZs) of Nyando sugar belt in Kisumu County. Sugarcane stalks above the age of nine months were randomly selected from each sampled farm and the presence of RSD was detected by phase contrast microscope and Tissue Blot Enzyme Immunoassay. Information on sugarcane variety, source of seed cane, acreage, and major sugarcane disease and production practices was collected using a questionnaire. Effect of hot water treatments in the 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 (25°C). The treated cane was planted in the field and in the greenhouse and data collected included germination, cane girth, cane height, number of millable stalks, number of internodes, cane weight and sucrose content. Results of the survey showed that 55% of the farmers grow sugarcane on small land holdings of less than two acres and mainly use seed cane from neighbours and own farms. Most farmers (96%) grow old sugarcane varieties such as CO421, CO945, CO617, and N14. Awareness on ratoon stunting disease was low, only 35% of farmers had information on the disease. Ratoon stunting disease was found to be highly prevalent (67%) in the Nyando sugar belt with disease xi incidence of up to 25%. All the three main varieties grown were found to have RSD incidences ranging from 10 to 35%. Hot water treatment at 45, 50 and 52°C significantly reduced RSD and increased cane germination, cane and sucrose yield. Hot water treatment at 55°C completely eliminated RSD but significantly reduced germination and cane yield. The cane setts which were treated with cold water at 25°C were stunted and had low overall cane yield. The results showed widespread occurrence of RSD in Nyando sugar belt which could be attributed to the use of infected setts, preference of old commercial sugarcane varieties coupled with low awareness to ratoon stunting disease. Hot water treatment at 50°C for two hours was the most effective and produced the highest cane yield. However results showed that cane yield at temperature 50°C and 52°C was not significantly different. Therefore any of the two temperatures are hereby recommended for management of ratoon stunting disease of sugarcane.
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