Giant knotweeds of the genus Reynoutria (syn. Fallopia)–Reynoutria japonica, Reynoutria sachalinensis, and a hybrid of them, Reynoutria x bohemica–are noxious invasive plants in Europe and North America. R. japonica is a traditional East Asian (Japan and China) drug (Polygoni cuspidati rhizoma). Recently, it has been included in European Pharmacopoeia as one of the traditional Chinese medicinal herbs. In this study, a reversed-phase high performance liquid chromatography method with diode array detector and time-of-flight mass spectrometry was developed and validated for the profiling of rhizomes from European invasive populations and Polygoni cuspidati rhizoma purchased in China. Twenty-five compounds were identified, mainly stilbenes, anthraquinones, flavan-3-ols, and phenylpropanoid esters. Tatariside B, hydropiperoside, vanicoside C, a new compound (3,6-O-di-p-coumaroyl)-β-fructofuranosyl-(2 → 1)-(2′-O-acetyl-6′-O-feruloyl)-β-glucopyranoside) were reported for the first time in these raw materials. Six compounds from three phytochemical classes–stilbenes: piceid and resveratrol; anthraquinones: emodin and physcion; hydroxycinnamic sucrose esters: vanicosides A and B–were quantified using the validated method. R. japonica from China contained twice as many stilbenoids than samples from Poland (piceid 14.83 mg/g dm vs. 7.45 mg/g and resveratrol 1.29 mg/g vs. 0.65 mg/g). R. sachalinensis rhizomes contained lower quantities of anthraquinones and no detectable stilbenes, which together with higher amounts of hydroxycinnamic glycosides makes it easily distinguishable from the other two. The phytochemical profile of R. x bohemica was intermediate between the two parent species.

Corn poppy (Papaver rhoeas L.) and cornflower (Centaurea cyanus L.) are two overwintering weed species found in crop fields in Europe. They are characterised by a similar life cycle, similar competitive efforts, and a spectrum of herbicides recommended for their control. This review summarises the biology and herbicide resistance phenomena of corn poppy and cornflower in Europe. Corn poppy is one of the most dangerous dicotyledonous weeds, having developed herbicide resistance to acetolactate synthase inhibitors and growth regulators, especially in Mediterranean countries and Great Britain. Target site resistance to acetolactate synthase inhibitors dominates among herbicide-resistant poppy biotypes. The importance of non-target site resistance to acetolactate synthase inhibitors in this species may be underestimated because non-target site resistance is very often associated with target site resistance. Cornflower, meanwhile, is increasingly rare in European agricultural landscapes, with acetolactate synthase inhibitors-resistant biotypes only listed in Poland. However, the mechanisms of cornflower herbicide resistance are not well recognised. Currently, herbicides mainly from acetolactate synthase and photosystem II inhibitors as well as from synthetic auxins groups are recommended for the control of both weeds. Integrated methods of management of both weeds, especially herbicide-resistant biotypes, continue to be underrepresented.

Summary: We analysed the effect of the invasive perennial plant Heracleum sosnowskyi on soil nematode communities and diversity, and plant species composition, by comparing invaded and non-invaded (control) areas in natural conditions. Invasion of H. sosnowskyi caused significant shifts in plant species composition, which subsequently modified nematode assemblages. Stress-sensitive omnivores, fungivores and root-biomass-dependent obligate plant parasites best reflected changes in soil nematode communities under the influence of H. sosnowskyi invasion. The negative effect of H. sosnowskyi was most evident on Aphelenchus, Tylencholaimus, Geocenamus, Helicotylenchus, Pratylenchus, Tylenchorhynchus and Aporcelaimellus. Our results indicate that significant changes in the herbaceous layer after H. sosnowskyi invasion in ecosystems where H. sosnowskyi eventually became dominant impacted soil nematode communities but did not affect nematode diversity. This was in contrast to the habitats where a solitary plant of H. sosnowskyi grew and no significant changes in nematode communities were observed.

Herbicide resistance in weeds, including corn poppy (Papaver rhoeas L.), is an increasing problem compromising global crop production. The aims of this study were to evaluate the susceptibility of P. rhoeas populations in Poland to acetolactate synthase (ALS) inhibitors and elucidate their mechanisms of resistance. Between 2017 and 2020, 157 seed samples were collected nationwide and a dose-response study with various ALS-inhibiting herbicides was performed in glasshouses. This revealed 14 resistant populations with R/S ranges of 2.3–1450.2, 9.5–398.5 and 2–2.5 for tribenuron, iodosulfuron and florasulam, respectively. Eight of them were cross-resistant to both tribenuron and iodosulfuron, three and one populations were singly resistant to tribenuron and iodosulfuron, respectively, and one population had reduced susceptibility to florasulam only. In one population, cross-resistance to tribenuron, iodosulfuron and florasulam was identified. The ED₅₀ of many populations susceptible to ALS inhibitors was close to half the recommended dose of the herbicides tested. In seven out of eight resistant P. rhoeas populations analysed, target-site resistance was identified. Six amino acid replacements were found (Ala197, Arg197, His197, Leu197, Ser197 and Thr197). In one population resistant to ALS inhibitors, no mutations in the ALS gene were detected. An efficient anti-resistance strategy is needed to reduce the development of herbicide resistance in P. rhoeas in Poland.