Phoma leaf spot and stem canker (Leptosphaeria species complex) development in winter oilseed rape

Leptosphaeria species complex (mainly Leptosphaeria maculans and Leptosphaeria biglobosq) causes phoma stem canker, the most harmful disease in winter oilseed rape (Brassica napus) in many European countries. This paper describes Leptosphaeria spp. ascospore release, phoma leaf infection, the development of phoma leaf spot and stem canker in 2004/05, 2005/06, and 2006/07 seasons on winter oilseed rape in Lithuania. The first circular phoma leaf spots with visible pycnidia developed on 10-28 October, 53-78 days after sowing of winter oilseed rape. In November 2004 there were 48.0%, in 2005 and 2006 - 28.0% plants with phoma leaf spots (mainly only one spot/plant). In 2005, before harvesting 72.0% of the assessed winter rape plants had symptoms of phoma stem canker of different severity on the crown, in 2006 and 2007 - 48.0 and 58.0% plants, respectively. Phoma stem canker before harvesting was found on 50.0-78.6% of plants with phoma leaf spot symptoms in the autumn, and only 1/3 of the plants with phoma leaf spots in the autumn were with severe (score 6) phoma stem canker on the crown before harvesting in 2005 and 2007 (in 2006 - 14.3%). Phoma stem canker on the crown was estimated on 47.2-88.5% of plants without clear symptoms of phoma leaf spot in the autumn, 16.7-26.9% of plants were with severe canker before harvesting. The average phoma stem canker severity index in 2005 was 4.04, in 2006 and 2007 - 2.24 and 2.22, respectively.