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Summary Several Fusarium species cause harmful cereal diseases, such as fusarium head blight and crown rot, which, during pathogenesis, may result in significant grain yield and quality losses. Several species of agricultural weed are believed to be alternative and reservoir hosts for Fusarium spp.; however, studies have not comprehensively evaluated those weed species in cropping systems that may harbour these fungi. The objective of this study was to determine weed species in cereal‐based crop rotations that are asymptomatically colonised by Fusarium spp. We sampled all species of weed present in fields that were managed under six different crop sequences in 2015 and 2016. The study yielded 2326 single‐spore isolates of Fusarium spp. derived from various organs of asymptomatic weeds. Isolates were identified morphologically and then confirmed using PCR with species‐specific primers and/or sequencing of tef1α gene fragments. Isolates of nine Fusarium spp. were obtained from 689 of the 744 individuals collected that represented 56 weed species. Each weed species harboured at least one species of Fusarium, and >80% were colonised by 3–9 Fusarium spp. In total, we identified 27 dicotyledonous weed species that were previously undocumented as Fusarium hosts and 251 new weed × Fusarium species combinations were revealed. Consequently, there is a greater risk of negative Fusarium impacts on cereal crops than was previously thought. We suggest effective weed management and inversion soil tillage may help mitigate these impacts.

Tillage not only changes soil properties but also serves as a weed control means. Different soil tillage systems were investigated in a long-term field experiment conducted during 2003-2012 at Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry. The experiment was carried out in a cereal-based crop rotation. The experimental design included the following tillage treatments: 1) conventional tillage (CT): mouldboard ploughing at 22-24 cm depth; 2) minimum tillage (MT): stubble cultivation at 10-12 cm depth, non-selective herbicide (glyphosate) spray applied after harvesting; 3) no tillage (NT): direct drilling, non-selective herbicide spray applied after harvesting. This paper presents the data from the 2007-2012 experimental period. To determine weed seed bank, soil samples were taken in 2007 after spring barley harvesting and in 2012 after winter oilseed rape harvesting. Samples of weeds for the determination of fresh and dry mass were collected in 2011 and 2012 in winter wheat and winter oilseed rape crops during the growing period. The weed seed bank in the soil significantly decreased over the five-year period. However, significantly the highest number of seeds in the soil was found in the no tillage plots. Significant differences in the weed species composition between the different tillage systems were recorded: no tillage system promoted infestation of some broadleaf weeds, particularly Capsella bursa-pastoris. The lowest weed mass was determined for the conventional tillage plots, compared to minimum tillage, and especially no tillage plots.