RESULTS OF THE SURVEY AND EVALUATION OF CASSAVA ROOT ROT DISEASE IN LÀO CAI PROVINCE

Abstract

Cassava root and tuber rot was detected in Yen Bai province (now Lao Cai province) and other northern mountainous provinces of Vietnam, threatening both cassava production and starch processing factories. A total of 180 diseased samples were collected from Yen Binh (Tan Huong), Bao Ai (Cam An), Yen Binh (Dai Dong), Mau A (Mau Dong), Dong Cuong and Chau Que (Chau Que Ha) communes of Lao Cai province.The disease was observed from the seedling stage to harvest across all surveyed varieties, with KM98 - 7 showing lower susceptibility than BK. In Yen Binh (Tan Huong) and Bao Ai (Cam An), where cassava is intercropped or rotated with other crops, disease incidence was lower than in Mau A (Mau Dong), Dong Cuong and Chau Que (Chau Que Ha), where cassava was intensively monocropped. Monthly disease incidence showed no significant effect on yield; however, rotten tuber incidence was strongly correlated with yield loss. A 1% increase in rotten tubers reduced yield by 0.73 t/ha (BK) and 1.3 t/ha (KM98 - 7) in Yen Binh (Tan Huong) and Bao Ai (Cam An), and by 0.83 t/ha (BK) and 1.4 t/ha (KM98 - 7) in Mau A (Mau Dong), Dong Cuong and Chau Que (Chau Que Ha).