This study aims to reveal the spatiotemporal variation of five major grass weed species, including Lolium multiflorum, in winter wheat fields of the Huang-Huai-Hai region over the past decade, and to provide a basis for regional weed monitoring, early-warning and precision management.

Two rounds of systematic surveys were conducted in winter wheat fields across the Huang-Huai-Hai region in 2013 and 2023 using an inverted “W”-shaped nine-point sampling method. The distribution ranges and infestation levels of five dominant grass weeds, including Aegilops tauschii, Bromus japonicus, Lolium multiflorum, Alopecurus myosuroides and Avena fatua, were recorded. The relationships between relative abundance (RA) and longitude/latitude were analyzed to characterize spatiotemporal distribution patterns.

The spatiotemporal changes in grass weeds in winter wheat fields of the Huang-Huai-Hai region were mainly reflected in the following aspects: (1) The relative abundance of four grass weeds, L. multiflorum, A. tauschii, B. japonicus and A. myosuroides, increased continuously, whereas that of A. fatua decreased slightly. In 2013, B. japonicus and A. tauschii showed the highest RA values in the region, together accounting for more than 15%, followed by A. fatua (2.51%), while L. multiflorum and A. myosuroides both had RA values below 2.5%. By 2023, the RA of A. tauschii(11.66%) and B. japonicus (11.22%) increased markedly. The maximum increase observed for A. tauschii was 8.72%, whereas B. japonicus exhibited increases ranging from 0.43% to 10.44%. The regional mean RA of L. multiflorum increased to 2.88%, exceeding that of A. fatua (2.14%) and becoming the third most abundant species. (2) Spatially, the infested area of L. multiflorum, A. tauschii, B. japonicus and A. myosuroides expanded continuously, while the distribution range of A. fatua shrank slightly. A. tauschii and B. japonicus expanded continuously eastward and southward from their traditional high-incidence belts in the western and northern Huang-Huai-Hai region; by 2023 they almost covered all major winter wheat production areas across the entire region, and relatively stable populations had formed in previously blank or sporadically infested areas such as the Huaibei region of Anhui and Jiangsu as well as Tianjin. In 2013, L. multiflorum and A. myosuroides occurred only sporadically in a few prefecture-level cities; ten years later, L. multiflorum was recorded in about 60% of the surveyed prefecture-level cities, rapidly shifting from “localized point occurrence” to a pattern of “southern concentration with regional spread”, and forming new high-incidence belts in central-southern Henan, northern Anhui, northern Jiangsu and the Guanzhong Plain, indicating strong expansion momentum and substantial potential risk. A. myosuroides formed concentrated high-incidence areas in the Guanzhong Plain, central-southern Henan, northern Anhui and central-southern Hebei, with its overall pattern changing from “point-like occurrence” to “patch-like expansion”. In contrast, the overall distribution range of A. fatua decreased; it was no longer recorded in some central and northern prefecture-level cities, and its main high-incidence belt shifted from the previous “wide distribution in southern and western areas” to localized concentration in central-southern Henan, northern Anhui and the Guanzhong Plain, showing a “southward contraction” pattern. (3) Correlation analyses showed that in 2013 the RA of A. tauschii was significantly negatively correlated with longitude, whereas in 2023 it was significantly positively correlated with latitude, indicating a weakened east-west gradient and an enhanced north-south gradient. The RA of B. japonicus increased highly significantly with latitude in both surveys, and in 2023, also showed a significant increasing trend with longitude. The RA of L. multiflorum and A. fatua generally decreased with increasing latitude and longitude, while A. myosuroides showed no consistent or significant correlation.

Over the past decade, major grass weeds in winter wheat fields of the Huang-Huai-Hai region have undergone marked spatiotemporal expansion, accompanied by increasing relative abundance. These changes are driven by the combined effects of alien invasion, conservation tillage, long-term reliance on single-site-of-action herbicides, and cross-regional movement of agricultural machinery and seeds. Accordingly, region-specific systems for weed monitoring, early warning, and integrated management, together with optimized tillage practices and herbicide mode-of-action rotations, are required to enable precision control of grass weeds across the Huang-Huai-Hai winter wheat system.

In the past 10 years, the weed communities in the winter wheat fields in Henan Province have changed significantly. The objective of this study is to clarify the succession of weed communities in the six major planting areas in Henan Province, analyze the reasons of weed succession, and to provide a theoretical basis for the establishment of accurate control strategy of weeds in winter wheat fields.

A total of 378 plots in 17 cities of Henan Province were sampled from November to December in the 2023 to investigate the weed species and weed number in winter wheat fields, compared with the results of 2013, the weed community composition in six major planting areas of winter wheat fields in Henan Province was determined, and the weed community change law was analyzed.

The characteristics of weed communities in winter wheat fields in Henan Province were: (1) Gramineous weeds developed rapidly, Aegilops tauschii, Lolium multiflorum, Bromus japonicas, and Alopecurus myosuroides gradually spread from the local area to the whole province, almost covering the whole province major planting areas at present. Among them, A. tauschii and B. japonicus mainly occurred in dry-stubble wheat fields. In 2013, 14th, 15th, 27th and 35th relative abundances of the four weeds were ranked, respectively, but relative abundances ranked 2nd, 5th, 8th and 15th, respectively, in 2023. (2) Galium aparine and Veronica persica had always been the dominant broad-leaved weeds in winter wheat fields in Henan Province, with relative abundance of 26.89% and 10.68% in 2023, respectively. In the past 10 years, two surveys showed that the comprehensive relative abundance of G. aparine ranked first, G. aparine caused great damage in both dry-stubble wheat field and rice-stubble wheat field, and V. persica had risen from 6th to 3rd. (3) G. aparine, A. tauschii, V. persica, and Descurainia sophia became the dominant weeds in winter wheat fields in Henan Province. In 2013, only G. aparine and Capsella bursa-pastoris had relative abundance of more than 10%, which was 17.38% and 10.92%, respectively, but in 2023, the relative abundance of G. aparine, A. tauschii, V. persica, and D. sophia exceeded 10%, which was 26.89%, 13.45%, 10.68%, and 10.65%, respectively. (4) The damage of regional dominant weeds was also serious, such as Lamium amplexicaule, Raphanus raphanistrum, Malachium aquaticum, Euphorbia helioscopia, Lithospermum arvense, and Geranium carolinianum. In addition, regional harmful weeds such as Lapsana apogonoides, Mazus japonicus, and Alopecurus aequalis were mainly distributed in rice-stubble wheat fields.

The changes of the weed communities in winter wheat fields in Henan Province are mainly caused by the changes of farming systems, the spread and invasion of malignant weeds and the development of weed resistance. Cross-regional operation of combine harvester and human unconscious carrying and spreading are also important factors to promote the change of weed community. Therefore, in the prevention and control of weeds in winter wheat fields in Henan Province, the integrated weed control strategies, such as combining chemical herbicides with agronomic measures, the precise selection of herbicides according to the field grass phase in different planting areas and using herbicides with different mechanisms, should be promoted.