Control stem white rot of rapeseed caused by Sclerotinia sclerotiorum with Coniothyrium minitans, focused on application time

摘要

Stem white rot of rapeseed caused by Sclerotinia sclerotiorum in China is a major obstacle for further improvement of seed yield. Coniothyrium minitans, a mycoparasite of S. sclerotiorun, was introduced to control this disease in field. To find out the optimal delivery time, conidia of C. minitans were aerially delivered onto plants at 5 % bloom, 10 % bloom and 50 % bloom at Xishui county, Tianmen county and Wuxue county of Hubei Province from 2004 to 2006. The efficiency of C. minitans on control stem white rot was evaluated via yield improvement and reduction of disease severity. Among 36 valid C. minitans treatments, 30 treatrments showed that the seed yields were improved with a range of 6.0 % to 27.3 %. C. minitans delivered at 5 %bloom and 10 % bloom gave higher efficiency than at 50 %; and applied twice (one at 5 % bloom and the other at 10 % bloom)gave the highest efficiency. The results also showed that C. minitans could reduce the disease severity when applied at 5 % bloom and 10 % bloom, however, the disease severity was not related to the loss of seed yield. In all experiments, dimethachlon was used as control, and results showed that this fungicide gave better efficiency than C. minitans did. This is the first time we evaluated the efficiency of C. minitans via seed yield of rapeseed. The potential of aerial application and the factors which may affect the efficiency of C. minitans against stem white rot were also discussed.