Agronomic implications of paraquat ban in Brazil

Abstract

Background

Paraquat is a broad spectrum herbicide used particularly in burndown, in pre-plant of row crops and in the pre-harvest desiccation of some crops. In Brazil, paraquat was re-evaluated by Anvisa, leading to a prohibition of production and sales on September 22, 2020, and used until July 31, 2021.

Objective

The objective of this review is to characterize the use of paraquat in Brazil and describe the status in other countries, particularly the agronomic implications of its ban, possible replacements, and scenarios.

Review

The use of paraquat is important for weed management in different production systems. Owing to its toxicity, its use has been re-evaluated in several countries. For pre-harvest desiccation of soybeans, diquat, glufosinate, and some combinations with Protox inhibitors are highlighted as alternatives to paraquat. For pre-harvest desiccation of common beans, diquat, saflufenacil, and glufosinate could be used; however, only glufosinate could be used for wheat. For managing broadleaves weeds, glufosinate, saflufenacil, carfentrazone, and diquat are effective alternatives. Diquat may be less effective in controlling Conyza spp. resistant to paraquat. For grasses control, glufosinate, in addition to ACCase inhibitors and possible mixtures, may be helpful. Although pre-emergent herbicides are not classified as desiccant herbicides, they contribute to weed management. The adoption of herbicide-tolerant crops, mechanical control, and cover crops can be added as agricultural practices for integrated weed management.

Conclusions

Due to the ban on paraquat, challenges arise, and the most often suggested replacements are glufosinate, diquat, and Protox inhibitors; however, grass control will be of greater concern.

Bipyridylium; weeds; pre-harvest; herbicides