Concentration of ascospores of Leptosphaeria maculans and L. biglobosa in the region of Wielkopolska in autumn 2011–2013Stężenie askospor grzybów workowych Leptosphaeria maculans i L. biglobosa w Wielkopolsce jesienią 2011–2013

Summary Two fungal species Leptosphaeria maculans and L. biglobosa cause stem canker of brassicas, one of the most important diseases of oilseed rape in Poland and worldwide. Ascospores are the primary inoculum responsible for the first leaf spot symptoms on plants. These spores originate from pseudothecia – sexual fruiting bodies formed on oilseed rape stubble from the previous season’s crop. Monitoring of ascospore release enables identification of the optimal time for plant protection by fungicide application. The aim of this work was to assess the risk of infection of oilseed rape in relation to ascospore concentration in the air. Experiments were performed in autumn 2011–2013 in the region of Wielkopolska. In subsequent years of studies the maximum concentration of ascospores per cubic meter of the air were: 86 (2011), 68 (2012), 30 (2013). In 2011 and 2012 the peak concentrations of spores were observed in October (9 October 2011, 23 October 2012) and in 2013 – on 27 September. In the period from the beginning of September to the end of November, ascospores were present in the air for c.a. 65% of days. The results indicate that oilseed rape fields in Great Poland are at great risk of stem canker, caused by Leptosphaeria maculans and L. biglobosa species complex.