Researchers from Embrapa, alongside the Brazilian Ministry of Agriculture and Livestock (Mapa) and its American counterpart, warn that used cotton harvesters imported from the USA are the main vectors of the spread of Amaranthus palmeri seeds in Brazil.. Amaranthus palmeri (also known as carelessweed, djoecious amaranth and Palmer's amaranth) is a plant that can cause large productivity losses in annual crops. It was initially detected in the state of Mato Grosso in 2015 and later found in Mato Grosso do Sul in 2022. According to Embrapa Soybeans researcher Dionísio Gazziero, carelessweed is a plant with difficult control, aggressive growth, high prolificacy and resistance to herbicides."That is why it is important that the harvesters are well cleaned and decontaminated. These measures reduce the risk of any seeds being left unnoticed. Cleaning prevents their introduction into new areas and it has to be done before the equipment is moved to another property, considering the seeds are very small and difficult to see, especially when mixed with residue within the harvesters," Gazziero explains. Carelessweed characteristically grows quickly. In ideal conditions these plants can grow from 2 to 4 cm per day. This fact can impair the effectiveness of post-emergence herbicides, as delayed application can reduce their effectiveness. For this reason, in areas that have problems with carelessweed it is very important to use pre-emergent herbicides to help in their control. Inadequate control can make harvesting unfeasible, increase the need for the use of herbicides, burden the cost of production, and cause enormous losses in Brazilian agriculture. The state research and agricultural defense agencies and Mapa are working to define strategies so that it does not spread. Prompt government decision-making and monitoring of compliance with preestablished phytosanitary measures, combined with the commitment of farmers and of public and private institutions, have contributed to the containment of this plant in infested areas. "However, the efforts require a federal Normative Instruction establishing basic guidelines to be followed in the event the pest is detected. Such regulation would help speed up pest containment measures", says Alexandre da Silva, a researcher at Embrapa Maize and Sorghum. "The presence of this new species of amaranth, which had not been recorded in our country, creates serious problems for soybean growers. The information on how this plant managed to enter Brazil serves as a warning to all farmers who import used machinery, to plant surveillance agencies, and to those who use machinery owned by third parties who move them from one area or state to another," Silva asserts. Embrapa Environment researcher Antonio Cerdeira explains that the plant is easily confused with other Amaranthus species that are common in Brazil. "If its presence is suspected, it is necessary to notify the local agricultural defense agency to identify and confirm the suspicion. When in doubt, farmers should eliminate the plant in their area to avoid proliferation," he states. The warning made by Mapa to state agricultural defense agencies and the field monitoring these institutions perform have allowed the early identification of some infested areas and have contributed to reducing the speed of spread of the species, preventing or delaying a new problem for Brazilian agriculture. Containment strategies After being classified as a quarantine weed, the carelessweed has been included in the Brazilian government's Official Pest Control Program. The state of Mato Grosso instituted the Amaranthus palmeri Containment Committee to support agricultural defense agencies (INDEA-MT) in activities to fight the weed. State agricultural inspectors were trained to identify the species and perform surveys in the states. Later on, agricultural defense agents from other states were trained and they included the observation of the occurrence of the weed in inspected crops in their routine. Then there were actions aimed at farmers, highlighting the importance of raising awareness of the problem, weed identification and control in the sector. The engagement of the agricultural community is essential to contain the pest. "It is important to reinforce and review the policy on inspection of imports of used machinery, as well as on the transit of machinery, especially between states, after the weed has been detected in Brazil," Gazziero says. More information on the characterization and management of Amaranthus palmeri can be found in Document 384 published by Embrapa. The full study was authored by Dionísio Gazziero, Alexandre da Silva, Omar da Silveira, Steve Duke and Antonio Cerdeira.