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Paraquat: agronomists and experts evaluate impact in Brazil
Nov. 17, 2015
The public consultation opened by the National Health Surveillance Agency about the toxicological re-evaluation of the active ingredient Paraquat ended this Monday (11.16). The agency defends a national ban of the active ingredient alleging that there are cases demonstrating the acute and chronic high toxicity of this substance.
According to the agronomist Josué Verba, an expert on marketing and strategy for the Crop Protection Market, the volume of Paraquat exported to Brazil is around 36 million liters of commercial product. According to him, the sale of the product is divided through the following: soybeans 53%; cotton, corn and sugarcane around 27%; kidney beans, potatoes, coffee and wheat 10% and other crops 10%.
In order to evaluate the technical questions pertinent to the re-evaluation of the molecule, the Doctor Fernando Storniolo Adega, who is an expert on weeds of Embrapa, clarified some issues.
Question: Taking into account the availability of other molecules and the importance of management, in which mode the loss of Paraquat would have more impact?
Adegas: Besides these two modes of Paraquat, it is also used in operation of weed control in annual and perennial crops in direct spray. Of these three modes, the first two cited, desiccation on pre-planting and desiccation of the crop for the harvest, are the main ones and the hardest to specify in which of them the loss of Paraquat would have more impact, because in both the impact would be great.
Question: Paraquat is classified as an inhibitor of photosystem I. Other member of the group is Diquat. What are the major differences of performance of these two products?
Adegas: The main difference is action spectrum, because the Paraquat has a good efficiency for the control of monocots and dicots, while Diquat controls basically dicot plants.
Question: What species of weeds would be specially impacted by the prohibition of Paraquat?
Adegas: In general, the control of all species in which the product is registered for would be affected. However, we consider that the greater impact would be on the species resistant to glyphosate, mostly ryegrass, the horseweed and the sourgrass.
Question: Taking into account the application of the pre-planting, what products or combinations would be the possible replacements? And at the application of desiccation of the crop?
Adegas: It would be difficult to find a general and only replacement of Paraquat because it would depend on each area and specific situation, where in most cases there would be really a necessity of use of combinations of herbicides and other systems of application, such as the sequential. The major herbicides that could be part of the control system would be glyphosate, ammonium glufosinate, saflufenacil, 2, 4-D and the diquat, for the desiccation of ple-planting; and the same herbicides with the exception of 2,4-D for the desiccation of crop, highlighting the necessity of verifying the existence of specific registration of this herbicide for each crop or mode of application.
Question: The current scenario shows the increase of species of resistant weeds and their geographic distribution and the appearance of new resistant species. How the loss of products such as Paraquat can impact the agricultural production in Brazil?
Adegas: Currently, in the case of resistant species to glyphosate the impact would be huge, because these plants like ryegrass, the horsewwed and the sourgrass have an important stage of control being done before the seedling of summer crops, specially soybeans, at the operation of dissection of the pre-seedling, on sequential applications or not, where Paraquat is one of the main herbicides used.
The below table lists the commercial brand and registering companies of Paraquat-based products, according to the Agrolinkfito system:
Source: AgroNews
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