Importance and status of sugarcane smut (Ustilago scitaminea) in the Ethiopian sugar estates
Sugarcane smut (Ustilago scitaminea) is considered as the most prevalent and serious disease in sugarcane producing countries of the world. To determine incidence of sugarcane smut, a total of 144 fields were surveyed at Wonji-Shoa, Metahara and Finchaa on plantcane, first and last ratoon crops from August 2008 to July 2009. Smut incidence varied significantly among the survey months within and across sites, among the varieties across sites and among crop types within and across sites. Among the sites, the highest incidence of the disease was recorded at Wonji-Shoa (3.78%) followed by Finchaa (3.61%) and Metahara (1.05%). Moreover, high number of affected stools was recorded during the months of June and July at Finchaa and from April to June at Wonji-Shoa. While at Metahara high number of smut-affected stools was recorded in April and May. Among the varieties, Co 421, mixed varieties (MV) and NCo 334 at Wonji-Shoa; NCo 334, NCo 376 and Mex 54/245 at Metahara and in NCo 334 and N 14 at Finchaa showed high incidence (> 10%) of smut. Low incidence (< 3%) of smut was observed on B58156 and B52298 at Wonji-Shoa; B52298, B41227, Co 678, Co 680 and MV at Metahara and B52298 and D 42/58 at Finchaa. The result also indicated that smut incidence increased as ratooning increases in all the plantations. Besides, long year data trend analysis on cane yield loss due to smut in the plantations revealed that there was a decreasing trend in the loss both at Wonji-Shoa and Metahara. However, the decreasing trend at Wonji-Shoa
was not significant (R2 = 0.49) as compared to Metahara (R2 = 0.88). Nonetheless, the loss due to the disease showed a significant (R2 = 0.91) increasing trend at Finchaa. Thus, the plantations need to strengthen smut management with special emphasis on use of disease-free planting material, resistant varieties and rouging efficiency. Sugarcane smut management control strategy should also treat each crop type and plantation differently.