Interactions between Weeds, Pathogen Symptoms and Winter Rapeseed Stand Structure

Rapeseed, weeds, and pathogens interact with each other. However, these interactions are not well understood. The aim of our work was to describe the relationships between weed vegetation and pathogen manifestations in rapeseed stands. Results from the four seasons show that different rapeseed stand structures produce different weed and pathogen responses. Eighteen weed species were identified in the rapeseed stands. The selected characteristics of rapeseed stands, pathogens, and weed manifestations were evaluated using redundancy analysis. Rapeseed stands with the highest levels of pathogens present (<i>Alternaria brassiceae</i> (Berk.) Sacc., <i>Botrytis cinerea</i> (De Bary) Whetzel, <i>Sclerotinia sclerotiorum</i> (Lib.) de Bary, <i>Verticilium longisporum</i> (C.Stark) Karapapa, Bainbr & Heale) had the lowest seed yield. There, the weeds <i>Cirsium arvense</i> (L.) Scop., <i>Tripleurospermum inodorum</i> (L.) Sch. Bip., <i>Sonchus arvensis</i> L. were more abundant in dense stands, and <i>Phoma lingam</i> (telomorph: <i>Leptosphaeria maculans</i> Ces. & De Not.) was more common. Mutual positive interactions may also include the relationship between weed species of the <i>Asteraceae</i> family and increased manifestations of <i>Phoma lingam</i>. A similar relationship can be expected for the weeds <i>Capsella bursa-pastoris</i> (L.) Medik., <i>Descurainia sophia</i> (L.) Prantl and <i>Sclerotinia sclerotiorum</i> symptoms.