The weed occurrence and control in single-crop late rice field in Jinshan District of Shanghai.

The weed species and their occurrence in the single-crop late rice field in Jinshan District of Shanghai in recent years and the weeding techniques were investigated by means of field survey, questionnaire,and symposium attended by influential farmers,technicians or experts.The investigation showed that Ammannia baccifera and Leptochloa chinensis became dominant species damaging direct-seeding rice,and Leersia hexandra var.japonica and plants of miscellaneous rice varieties rapidly increased in injurious effect and became major injurious weeds.Some suggestions were put forward in dealing with the present problems such as weeding techniques difficult to be mastered and high weeding cost.