MYCOCENTROSPORA ACERINA IN CARROTS - EFFECTS OF CROP-ROTATION ON DISEASE INCIDENCE

Four experimental sites located in different climatic regions in Norwa y were inoculated with Mycocentrospora acerina in 1985. In 1986, crop rotation experiments including carrot, barley, grass, red clover, onio n and potato, were established at these sites. Incidence of M. acerina on the foliage and the roots of carrots after storage were recorded i n 1989/90 and 1994/95. The 3 yr rotation only slightly reduced the ino culum of M. acerina in the soil. Red clover and grass were the most ef fective crops in reducing the inoculum, potato and barley were less ef fective, and onion had no effect on the inoculum. Differences in M. ac erina infection on carrots between 3, 6 and 8 yr of rotation with barl ey and grass were not statistically significant.