Rice weeds attack rice plants in the winter-spring crop.

Throughout the 2023-2024 winter-spring rice crop fields of Tánh Linh district, from ripening rice to flowering rice and rice in the heading stage, rice is being attacked by mixed rice varieties (wild rice, forest rice, two-tiered rice). Almost all rice varieties grown this season are affected. The most severe infestations are in the areas belonging to the communes of Đồng Kho, Đức Bình, Đức Thuận, and Lạc Tánh town.

According to observations, in the large rice field area of Lac Thanh town, mixed rice varieties are present in almost all rice fields currently in the flowering stage. Mr. Nguyen Manh, who cultivates 5 sao (approximately 0.5 hectares) of rice in this winter-spring crop, said: "In previous years, there were mixed rice varieties, but very few. This winter-spring crop, however, there are a lot of them. My family has already spent time cutting them down twice, but they are still not completely gone, and we are currently continuing the third attempt to remove them."

In the fields of Dong Kho commune, where many rice paddies are cultivated under a business-linked farming model, there is also mixed rice. In these linked areas, the rice is ripe and ready for harvest, and the businesses are continuing to hire workers to remove the mixed rice.

According to farmers, it's common for rice fields that were contaminated with mixed rice varieties in previous years to be contaminated again, but many fields that were previously unaffected are now also being contaminated. Because the price of rice seeds is currently very high, fluctuating around 20,000 VND/kg, some farmers buy seeds from unreliable sources, resulting in a high incidence of mixed rice. Therefore, farmers have identified the seed as one of the main causes of mixed rice. Fields heavily contaminated with mixed rice varieties will experience reduced yields and lower rice quality.

Mr. Mai Tri Man, Deputy Head of the Agriculture and Rural Development Department of Tanh Linh District, said: For the 2023-2024 winter-spring crop, the entire district cultivated a total area of 11,552 hectares, of which 9,019 hectares were planted with rice. The main rice varieties used were OM4900, OM5451, OM6976, OM7347, OM2395, and ML202. Currently, about 2,000 hectares of rice are being harvested, while the remaining rice is in the flowering and heading stages. Many areas of the winter-spring rice crop are currently infested with mixed rice varieties. The initial cause has been identified as mixed rice appearing on different rice seed sources, especially in fields where weeds previously grew. In this winter-spring season, weeds are growing even more, and in higher fields where water availability is insufficient and drought conditions are causing weeds to grow more and develop rapidly. Weed seeds easily fall off, creating a ready source of residual seeds in the soil and spreading to the next crop. Therefore, fields that are not thoroughly plowed and harrowed, and where weeds are not treated before planting, will experience faster and more widespread weed growth. Harvesters that are not properly cleaned after harvesting from weed-infested fields to uninfested fields are another reason why weeds persist in the soil. Many farmers buy low-quality, low-cost seeds from unreliable sources, resulting in weeds already present in the seeds when sown.

To protect crops and limit and control the widespread damage caused by weeds and their spread to subsequent crops, the District Department of Agriculture and Rural Development has advised the District People's Committee to direct local authorities to instruct farmers to cut weeds as soon as they appear and destroy them, not discarding them indiscriminately on field edges or in irrigation canals, to prevent further spread. Harvesters should be cleaned thoroughly before harvesting to prevent the spread of weed seeds from infected areas to uninfected areas. After harvesting the winter-spring rice crop, flood the fields with water and plow to encourage weed growth and use methods to eradicate them before planting the summer-autumn crop. Select rice seeds from reliable sources. Simultaneously, establish production linkages and product buyback agreements with businesses to ensure compliance with production processes, resulting in higher rice yields and quality.

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