Proactive weed management protects summer-autumn rice yield

Proactive early-season weed control

The Mekong Delta is entering the peak of the summer-autumn rice production season amid increasingly unpredictable weather conditions. Frequent early-season rains following a prolonged period of hot and dry weather have created favorable conditions for the rapid emergence of various weed species, including sedges, nutgrass, barnyard grass, sprangletop, and feathergrass. This has become a major challenge for farmers right from the start of the cropping season.

According to agricultural specialists, weeds compete directly with rice plants for nutrients, sunlight, and water, particularly during the early growth stages when rice seedlings are still vulnerable. If not controlled promptly, weeds can spread rapidly, reducing tillering, causing uneven crop development, increasing the risk of pest and disease outbreaks, and significantly raising production costs.

In Dong Thap Province, one of the Mekong Delta’s largest rice-producing areas, weed management has long been a major challenge for farmers. Many growers have had to increase the number of herbicide applications and spend more on labor, yet weed control results often fall short of expectations.

While showing us his five-hectare Long An glutinous rice field that had recently undergone early-season weed treatment, Mr. Mai Van Hai, a farmer from Phu Loi Hamlet, An Long Commune, Dong Thap Province, said that in previous years his family typically had to apply herbicides two to three times per crop, yet weeds would quickly re-emerge.

“This season, technical advisors recommended a combination of Betazol and Vitanil. With just one application, weed pressure was significantly reduced. The field is now much cleaner, and the rice plants are growing uniformly and covering the field surface well,” Mr. Hai said.

According to Mr. Hai, prolonged hot weather followed by heavy early-season rains this year created favorable conditions for difficult-to-control weeds such as sedges and feathergrass, resulting in higher weed pressure than in previous seasons. However, thanks to early intervention, the rice crop has developed well, with vigorous tillering and improved field aeration, helping reduce pest and disease pressure later in the season.

Not only in An Long Commune, but farmers in Tan Hong Commune have also reported severe weed infestations following the first rains of the season. Mr. Ngo Van An, a farmer from Hamlet 3, Tan Hong Commune, said that early-season weeds such as nutgrass, feathergrass, and sedges grow rapidly and can cover an entire field within just a few days if left untreated.

“In the past, I used various herbicides, but their effectiveness against hard-to-control weeds was often limited. This season, Vipesco’s technical staff provided detailed guidance, so I decided to try the combination of Vitanil and Betazol for early-season weed control, and the results have been very encouraging,” Mr. An said.

According to Mr. An, weed populations declined noticeably within just a few days of treatment, particularly difficult species such as sedges and nutgrass. Cleaner fields have allowed rice plants to develop more uniformly, with stronger root systems and improved tillering.

An integrated solution for lower production costs

Many farmers believe that early-season weed management is no longer merely a technical measure but a key factor determining the economic success of an entire rice crop. Mr. Nguyen Phuong, a farmer in An Hoa Commune, explained that if weeds are allowed to proliferate during the early growth stages, rice plants become weakened and develop unevenly. Once this occurs, even increased fertilizer applications later in the season are often unable to fully restore crop performance, while production and management costs rise substantially.

Based on observations from multiple demonstration fields, Mr. Phuong noted that early weed-control measures have delivered clear and tangible results. Weed-free fields allow rice plants to grow more vigorously, reduce pest and disease pressure, and significantly lower the labor required for manual weeding.

According to the Southern Crop Production and Plant Protection Center under the Department of Plant Production and Protection, the period from June to August each year is when a wide range of pests and diseases are likely to develop on a large scale. In addition to weed infestations, farmers must contend with threats such as brown planthoppers, rice leaf folders, rice blast disease, and bacterial infections. As a result, agricultural authorities recommend an integrated crop management approach that includes thorough land preparation, early weed control, proper water management, balanced fertilizer application, and regular field monitoring to detect pests and diseases at an early stage.

Mr. Nguyen Thanh Phong, a technical officer with Vietnam Pesticide Joint Stock Company (Vipesco) in the Dong Thap Muoi region, explained that this year’s pattern of prolonged heat interspersed with early-season rainfall has created favorable conditions for difficult-to-control weed species to thrive.

“In fields located on higher ground where water retention is limited, weeds can spread very rapidly if they are not controlled at the beginning of the season. They compete aggressively with rice plants for resources and directly affect tillering performance,” Mr. Phong said.

Based on field observations, Vipesco’s technical team recommends a combination of Vitanil and Betazol to manage hard-to-control weed species such as sedges, nutgrass, feathergrass, and udu weeds. According to Mr. Phong, the key advantage of this solution is its ability to provide effective weed control early in the crop cycle, keeping fields open and weed-free, promoting uniform crop growth, increasing productive tillers, and ultimately contributing to higher yields.

To achieve optimal results, farmers are advised to control weeds at an early stage, when they are still small and more susceptible to treatment. Proper dosage and water management following application are also critical. For rice fields aged 10-15 days after sowing, the recommended rate is approximately 120 ml of Vitanil combined with 120 ml of Betazol per 25-liter tank of water. Water should be reintroduced into the field about 24 hours after application to enhance weed-control effectiveness.

Field monitoring across numerous demonstration plots in the Dong Thap Muoi region has shown weed-control efficacy ranging from 95% to 100%, particularly against hard-to-control weed species. Early removal of weeds enables rice plants to tiller more vigorously, reduces labor requirements, and minimizes the need for additional treatments later in the season.

Toward sustainable rice production

Field observations from across the Dong Thap Muoi region indicate that this year’s summer-autumn crop has faced significant challenges. Prolonged periods of extreme heat, coupled with unstable water availability at the beginning of the season, have left many fields dry and cracked, creating favorable conditions for weed populations to develop more aggressively than in previous years.

Mr. Nguyen Duc Trong, Regional Manager for the Dong Thap Muoi area at Vipesco, explained: “If weeds are not controlled early in the season, they compete with rice plants for nutrients, sunlight, and water, resulting in weaker growth, reduced tillering, and ultimately lower yields. In addition, weeds serve as reservoirs for pests and diseases such as brown planthoppers, rice leaf folders, rice blast, and harmful bacterial pathogens.”

According to him, early weed management enables farmers to save considerable costs compared with delaying treatment until weed populations become well established. Beyond providing technical solutions, Vipesco’s field technicians regularly visit farms throughout the crop cycle to monitor rice growth and offer tailored recommendations to farmers at each stage of production.

As agricultural input costs continue to rise and farming systems face increasing pressure from climate change, effective weed-management solutions that reduce labor requirements and minimize the number of spray applications are becoming increasingly important. These approaches not only help lower production costs but also contribute to more sustainable and resilient rice production systems in the Mekong Delta.

Effective early-season weed management not only helps reduce production costs but also contributes to healthier rice fields, limits pest and disease outbreaks, improves farming efficiency, and supports the transition toward more sustainable agriculture in the Mekong Delta.

Field experience in Dong Thap Province shows that when farmers proactively control weeds at an early stage, while simultaneously adopting integrated technical measures and strengthening partnerships with agribusinesses, rice production efficiency improves significantly. This approach is considered a key pathway for the Mekong Delta's rice sector to better adapt to climate change, lower production costs, and enhance the value of rice production.