Canola disease situation in North Dakota, U.S.A., 1993-2004

Canola (Brassica napus) production in the United States (U.S.) has ranged from approximately 400,000 to 600,000 ha harvested annually in recent years. The state of North Dakota, located in the northern U.S., produces approximately 90 % of the entire U.S. canola crop annually. Field surveys have been conducted annually since 1993 to determine the prevalence and distribution of canola diseases in the state. In general, diseases measured in the surveys were Sclerotinia stem rot (Sclerotinia sclerotiorum), blackleg (Leptosphaeria maculans), Alternaria black spot (Alternaria brassicae, A. japonica), and aster yellows. Through all of the years of the survey, Sclerotinia stem rot has been an important disease, especially in seasons with cool, wet weather during the flowering period; however, with the registration of efficacious fungicides in recent years (beginning 2001), the incidence of Sclerotinia stem rot has been reduced somewhat. Blackleg has also been an important disease of canola in North Dakota. The use of cultivars resistant to pathogenicity group (PG) 2 kept blackleg incidence low until 2003. In 2003, PG 3 and PG 4 isolates were found in North Dakota, and blackleg incidence in 2003 and 2004 have been the highest in the 1993 – 2004 period of the surveys. Key words: canola, disease, surve