Weed control is an important part of crop production. In general, agronomic practices that produce a healthy, fast-growing crop provide the best protection against weeds. However, the single method of weed control or the continuous use of the same herbicide program have resulted in the emergence of resistant weeds. In Argentina, the area affected by resistant weeds has grown considerably, raising the cost of crop production.
The first case of resistance in Argentina was uncovered in 1996. Yuyo Colorado (Amaranthus quitensis) biotypes were found to be resistant to herbicides that included inhibitors of the enzyme acetolactate synthase (ALS), such as imazethapyr, chlorimuron ethyl, and flumetsulam. In 2005 and 2006, glyphosate resistance in sorghum biotypes of Aleppo was registered, and studies in 2007 in the southwestern section of Buenos Aires Province found ryegrass (Lolium spp.) resistant to this active ingredient. In 2008, the growth of Cynodon hirsutus (also known as Gramilla mansa) was confirmed in the center of Cordoba, along with Raphanus sativus (also known as Nabón) in the southeast region. More recently, Eleusine indica (also known as goosefoot) was identified in the center of Cordoba. The area affected by resistant weeds has been increasing yearly. At present, some 18 herbicide-resistant weed species can be found in Argentina, where different modes of action have no effect.
In Argentina, it was estimated that after the adoption of RR soybean, weed control was performed mainly with herbicides. In most farming countries, the presence of herbicide-resistant or tolerant weeds is attributed to the repetitive use of an active ingredient or poor crop rotation, typically the result of poor practices. So it is important to consider cultivation, rotation, and other effective cultural practices for weed control alongside herbicide treatments when developing a weed control program.
Global crop protection companies, research associations such as the National Public Research Institute of the Ministry of Agriculture (INTA) and the Argentine No Till Farmers Association (AAPRESID), and Crop Life Latin America have been taking action to help farmers and communities understand the situation in Argentina.
This cross-sectoral cooperation and appropriate communication aims to minimize the effects of weed population changes, which have an adverse impact on crop production. This strategy is aligned with the goals of sustainability and protection of the environment.
AAPRESID has been helping farmers change their attitude toward this situation and improve their technical management.
They created Red de Conocimiento En Malezas Resistentes (REM) as a collaborative network to share knowledge and information on resistant weeds. AAPRESID also coordinates activities, counting among its active members technical institutions, experts, and crop protection companies. It is known for monitoring and reporting on situations to assist early detection efforts. Farmers are invited to inform them of cases that are then published on the REM website, which discusses the actions needed to control the situation.
INTA also suggests combining tools such as integrated weed control with other technologies that are not exclusively based on herbicide usage. The institute believes effective weed control must have a low environmental impact and an application program should be sustainable over time.
The management of herbicide-resistant populations and prevention of further outbreaks in addition to chemical control requires a series of tactics. Rotation of active ingredients and even chemical herbicide families are not sufficient for resistance management. INTA researchers suggest a rotation of modes of action, facilitated by crop rotation.
CropLife Latin America
Favoring the responsible use of agro-technologies, CropLife Latin America developed the “CuidAgro program,” with an investment of over US$2 million, employing 196,580 people who were trained in 18 countries across Latin America.
The CuidAgro program promotes good agricultural practices through education on the responsible use of pesticides, the proper use of personal protection equipment, and integrated pest management. This information is shared with farmers for the following purposes:
• Prevention: by considering the conditions that can affect the crop, such as location, pesticide variety, staggered plantation, rotation, nutrition, responsible soil and water management, and biodiversity protection.
• Monitoring: to identify and distinguish beneficial insects from pests, weeds, and diseases.
• Intervention: to stop the advance of pests with cultural, biological, and chemical controls.
To combat the problem of resistant weeds, DuPont has been working on sustainable weed management and the development of useful products.
Under its sustainable weed management program, DuPont provides technical support and recommendations for their products to be included in weed strategies. It emphasizes the use of products and herbicides with different modes of action and the need for rotation, and it positions its own products to solve specific problems, urging farmers to avoid using a single active ingredient throughout the season.
DuPont aims to include in its portfolio at least two modes of action. For the current crop season, a product combining ALS with PPO inhibitors will be launched.
Bayer estimates that weeds are already destroying enough food to feed 1 billion people, and with resistant weeds on the rise, the damage may be even greater in the future. They have been giving farmers a toolbox of available products and practices to combat the build-up of resistance. They also launched an Integrated Weed Management Program that includes guidelines to help prevent resistance and may lead to a decline in the density of resistant populations.
The program offers a balanced combination of three components to enhance farmers’ productivity and secure food supplies in the long term. The integrated weed solutions can be implemented locally according to best weed management practices based on the latest scientific insights and supported by valuable partnerships.
In August 2014, BASF launched Programa Expertos en Malezas (PEM), or Expert Weed Program, during an AAPRESID convention in Argentina. It was developed to achieve effective control of weeds based on a management model that focuses on the combination and rotation of active ingredients and different modes of action.
The goal of this program is to help farmers with their decision-making process to control weeds and provide recommendations on good practices that fit their regional needs. In addition, they offer technical support to the farmers using collaborative tools, such as their website and 70 field technicians who provide technical support. The portfolio of the program comprises 20 herbicides and 9 different modes of action that are offered with other solutions to achieve effective control over weeds.
Syngenta has its own program called “No Malezas” (No Weeds). It features a set of combined strategies that allow farmers to achieve better control over herbicide tolerant and resistant weeds. No Malezas by Syngenta aims to offer a sustainable system to prevent weed problems. Detailed information on herbicides can be found on the company's website, along with the classification of modes of action groups.
No Malezas also considers rotation programs, active ingredients, and modes of action, suggesting crop rotation schedules and specific measures for each potential problem.
The program includes expert technical advice and the most complete line of herbicides to address a variety of problems.
ADAMA recently coordinated a study with the University of Buenos Aires on the economic impact of resistant weeds in Argentina. The research paper explained the concerns related to modern agricultural production based on the use of homogeneous crops and inorganic fertilizers and the application of herbicides, insecticides, and fungicides.
It was also estimated that the total cost of controlling resistant weeds in Argentina was US$1,300 million. Moreover, if the degree of weed infestation were to reach 90%, the potential loss in terms of production would amount to 17 million tons of soybeans.
These joint efforts between institutions, companies, technicians, and farmers are Argentina's current solution for facing this situation of resistant weeds, creating a network with the goal of minimizing any drops in yields and ensuring the sustainability of the evolving crop-production systems.