EN 
PT_BR 
The Paraná Agricultural Defense Agency (Adapar) is developing a set of actions for the prevention and control of the pest. Palmer amaranthus (Giant amaranth). The planning and execution of the actions take place after the plant was detected by the Agricultural Defense Coordination (CDA), linked to the Secretariat of Agriculture and Supply of São Paulo, in the São José do Rio Preto region. Traces were identified in January in a soybean plantation, and laboratory confirmation occurred on February 3rd.
Photo: Press release/Adapar
The strategy for agricultural and livestock defense in Paraná is to adopt rigorous preventative measures to avoid the introduction of this species into the state. Giant amaranth is an aggressive plant species that spreads easily. The Ministry of Agriculture and Livestock (MAPA), recognizing the possibility of its dispersal, issued a decree... SDA/Mapa Ordinance No. 1,119/2024, which establishes the National Program for the Prevention and Control of the Present Quarantine Pest Amaranthus palmeri.
Prevention measures
To date, four prevention and control measures have been defined to prevent the introduction of Giant Amaranth into the territory of Paraná. Direct inspection is one of them. Inspections will be carried out on properties and at locations receiving machinery from other states. The objective is to identify the presence of plants similar to Giant Amaranth early on.
Another preventive measure is sanitary education. During inspections, agency staff must instruct producers and operators on the mandatory rigorous cleaning of machinery. This action aims to mitigate the risk of seed dispersal to new areas. Adapar Ordinance No. 129 of 2024 provides guidance on the inspection of agricultural machinery and implements.
Sample collection is also part of the strategy. The procedure takes place immediately after suspected cases are identified and
Photo: Marlon Bastini/Embrapa
The protocols for sample collection are followed. The samples are sent to the Marcos Enrietti Diagnostic Center (CDME), linked to Adapar, for definitive laboratory analysis.
Using molecular biology tools, the CDME promotes the taxonomic distinction between the various species that make up the genus Amaranthus. The goal is to detect quarantine pests early and identify the most common species in production areas. Polymerase Chain Reaction (PCR) tests are performed, a high-precision molecular laboratory technique that amplifies specific segments of DNA or RNA to detect microorganisms (viruses, bacteria) or genetic mutations.
Operational support is the final step to be taken and is mainly present in the reconnaissance and sample collection phases for testing. The goal is for the agricultural defense inspectors and assistants from Paraná to provide technical support to local teams. These officials will also be responsible for monitoring state borders, acting as the first line of defense for agricultural and livestock protection.
Risks posed by the pest
The head of the Agricultural and Forestry Crop Health Division, Marcílio Martins Araújo, explained the risks posed by the pest. “It is a plant with a great capacity for competition with other cultivated plants, difficult to control, and with a very efficient capacity for multiplication and dispersal, which makes it a phytosanitary threat to Brazil and all its states. The multiplication potential of a female plant can reach figures of 600,000 to 1,000,000 seeds, which form a persistent seed bank that can remain in the soil for several years,” explains the agronomist.
Photo: Disclosure
In addition to the ease of creating a seed bank, the plant also has staggered germination, which is concerning because the seeds germinate in bursts throughout the growing seasons, making control with just one herbicide application insufficient.
The rapid growth of two to three centimeters per day can suffocate invaded cultivated crops. Furthermore, unlike other species in the state that are monoecious (i.e., possessing both male and female reproductive organs on the same individual), the Giant Amaranth is a dioecious plant, with separate male and female plants, which favors genetic variability and resistance. Constant vigilance is fundamental to prevent the spread of this pest throughout our states.
History
Giant amaranth was officially identified in Brazil in 2015. The first records occurred in cotton, soybean, and corn production areas in the state of Mato Grosso. The notification was made by technicians from the Mato Grosso Cotton Institute (IMAmt). This exotic weed exhibits high resistance to herbicides and has spread to other states, such as Mato Grosso do Sul and, more recently, São Paulo.
The species is native to North America and the south-central United States. Its first appearance in Brazil confirmed its resistance to glyphosate, a herbicide that acts on a wide range of weeds and is relevant in the production of fruits, vegetables, nuts, and resistant crops such as corn and soybeans. It is effective in controlling invasive and harmful weeds.
Since its introduction to Brazilian territory, the pest has been monitored, with subsequent reports in Mato Grosso do Sul in 2022 and São Paulo in 2026. Confirmation of the pest's incidence results in losses in various crops and in the economy of the affected region.
