Plant invasion is a big challenge to weed management of agricultural lands. In order to reveal the list of common weed species among alien invasive plants, and reveal practical management strategies, we extracted the species lists of common alien agricultural weeds (CAAWs) of various arable lands and plantations, by comparing the lists of alien invasive plant species and common weed species published in China. Totally 88 species from 18 families were recognized as CAAWs, among which 43.0 % are native to North America, followed by South America (34.4 %), Europe (29.0 %), Asia (23.7 %) and Africa (17.2 %); 62.4 % were introduced into China from 1840 to 1949. CAAWs such as Aegilops tauschii Coss., Alopecurus myosuroides Huds., Lolium multiflorum Lamk, Avena fatua L., Phalaris minor Retz, Phalaris paradoxa L., Veronica persica Poir., Geranium carolinianum L., Ranunculus muricatus L., and Cerastium glomeratum Thuill. frequently infest highlands with summer-ripe crops such as wheat and oilseed rape; Alternanthera spp., Panicum repens L., Paspalum conjugatum Bergius, and Ageratum conyzoides L. frequently infest highlands with autumn-ripe crops; and Paspalum distichum L., Alternanthera philoxeroides, and Ammannia coccinea Rott. occasionally infest rice fields. Troublesome CAAWs in plantations in China mainly consist of tall herbs, and climbing or spiny plants, such as Mikania micrantha Kunth, Ipomoea spp., Solidago canadensis L., Erigeron spp. and Bidens spp. Management strategies against CAAWs in current China mainly rely on chemical control, tillage, soil mulching, and manual removing of weeds. Next, effective risk assessing models targeting to different sorts of arable lands or plantations are urgently needed; as well, effective, feasible and sustainable integrated management strategies against troublesome CAAWs should be developed and applied.

Native weeds have a long history of adaptation to local environments. Understanding the relationship between the occurrence of native weeds and their life history traits is crucial for effective weed management and risk assessment of plant invasions. In this study, we surveyed native weed species and their dominance across 666 field sites in agricultural areas of Yangzhou City, China, and each site was 13.3 hectares in area. A total of 287 native weed species were recorded, referring to 63 families, among which 45% were 50–100 cm in plant height and 47% were of an erect life type. In terms of the proportions out of the total native weed occurrence dominance, Poaceae, Compositae, and Fabaceae weeds accounted for 30%, 13%, and 11%; liana and perennials both occupied 32%; and aquatic, hygrophyte, sun plant, and shade plant all occupied < 10%. Additionally, the proportions increased with increasing seed production per plant and with increasing weediness reported worldwide. Native weed groups holding moderate vegetative reproduction abilities, moderate seed sizes, or herbicide resistance showed higher proportions. Moreover, most of the native weeds surveyed were not succulent or thorny plants and did not hold thorns, awns, obvious hairs, or mucilage on their fruits.

Echinochloa crus-galli var. crus-galli (L.) P. Beauv. (EC), Echinochloa crus-galli var. mitis (Pursh) Petermann (ECM), and Echinochloa glabrescens Munro ex Hook. f. (EG) are all serious rice (Oryza sativa L.) weeds that are usually treated as a single species in weed management practices. To determine interspecific and intraspecific differences in seed germination responding to different temperatures among the three Echinochloa weeds, we conducted field surveys and collected 66 EC, 141 ECM, and 120 EG populations from rice fields of East China in 2022; and tested their seed germination under 28/15 C (day/night), 30/20 C, and 35/25 C regimes, simulating temperatures of rice-planting periods for double-cropping early rice, single-cropping rice, and double-cropping late rice, respectively. In EC, ECM, and EG, seed percentage germination (cumulative percentage of germinated seed) and germination index (sum of the ratio of germinated seeds to the corresponding days) increased with increasing temperatures. At 28/15 C, the average percentage germination of EC populations (67.5%) was significantly (P < 0.05) higher compared with ECM (46.4%) and EG (43.7%); GD₅₀ (duration for 50% total germination) for EC populations (5.2 d) was significantly shorter compared with ECM (5.9 d) and EG (5.8 d). At 35/25 C, the percentage germinations of EC (90.7%), ECM (80.5%), and EG (80.3%) were all significantly the highest among the three temperature treatments, respectively, and the GD₅₀ values for EC (2.5 d), ECM (2.6 d), and EG (2.7 d) were all significantly the lowest. At 30/20 C and 35/25 C, the average germination percentages of populations collected from transplanted rice fields were significantly higher than those of populations collected from direct-seeded rice fields. Moreover, among EG populations, the longitudes and latitudes of collection locations were significantly correlated with seed percentage germination and germination indices. According to the interspecific differences and intraspecific variations of Echinochloa species, weed management strategies should also be customized according to the species and population characteristics in seed germination.