Rice is the largest food crop in China. There are many kinds of weeds in rice fields, and the occurrence of weeds varies from place to place. There are about 200 kinds of weeds in rice areas in China, of which about 40 are common and seriously harmful. Among the main weeds, barnyard grass has the largest occurrence and damage area, followed by sedge, Hedyotis diffusa, lentil grass, Euphorbia fischeriana and potato.

The main weeds in the northeast and northwest middle-cold temperate single-season rice areas are barnyard grass, POTAMOGETON crispus, POTAMOGETON crispus, cow felt, POTAMOGETON crispus, iris, Spirogyra and so on.

The main weeds in the one-season rice area in the warm temperate zone of North China Plain are barnyard grass, heteromorphic sedge, POTAMOGETON crispus, cow felt, amaranth, duck grass, sedge, POTAMOGETON POTAMOGETON, Hedyotis diffusa, Spirogyra, iris, purple sweet potato, purple sweet potato, duckweed, spatholobus stem and so on.

The main weeds in subtropical rice areas in the Yangtze River Basin are barnyard grass, heteromorphic sedge, cow felt, sedge, POTAMOGETON crispus, POTAMOGETON crispus, broken sedge, Hedyotis diffusa, arrowhead, amaranth, Euphorbia fischeriana, Alternanthera philoxeroides, Commelina communis, Cynanchum komarovii and so on.

The main weeds in the subtropical rice areas of Yunnan-Guizhou and Qinghai-Tibet Plateau in the first and second seasons are barnyard grass, iris, Cyperus heterophylla, POTAMOGETON crispus, Hedyotis diffusa, Alisma orientalis, cow felt, POTAMOGETON crispus, Cyperus crispus, Ipomoea aquatica, Microcystis and Odontobutis sinensis.

The main weeds in tropical and subtropical double cropping rice areas in southern China are barnyard grass, heteromorphic sedge, Lycopodium japonicum, Polypodiaceae, Hedyotis diffusa, Sagittaria dwarf, Leymus chinensis, cow felt, sedge, crushed sedge, Spatholobus suberectus, apple and so on.