Bitter grass - Clumps of damage

Relentless tussock

Weed resistance to herbicides is not a new topic for Brazilian agriculture. In the nineties, with the use of traditional herbicides, producers were already faced with problems associated with the resistance of weeds such as marmalade grass, black pickerel and wild peanut.

With the advent of genetically modified crops with tolerance to glyphosate, an important tool has emerged to manage weed resistance problems, since glyphosate is a broad-spectrum, highly efficient herbicide. The intensive use of glyphosate, however, has brought new resistance problems, such as horseweed (Conyza spp.), ryegrass (Lolium perenne ssp. multiflorum), white grass (Chloris elata) and bittergrass (Digitaria insularis).

The first case of bittergrass resistance to glyphosate in the world was recorded in 2005 by researcher Fernando Adegas (EMBRAPA SOJA) when the existence of resistant biotypes was reported in soybean crops in Paraguay. In 2008, in a region geographically close to the first focus of resistance, the first case of bittergrass resistance to glyphosate was found in soybean crops in Paraná, in the municipality of Guaíra. And in 2011, the presence of resistant plants was reported in orange orchards in the Matão region, São Paulo. Currently, it is known that populations of bittergrass resistant to glyphosate are spread throughout the South, Central-West and Southeast regions, as well as some areas in the Northeast of Brazil.

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Rubem Silvério de Oliveira Jr.

Hudson Kagueyama Takano

Jamil Constantin

Center for Advanced Studies in Weed Science (NAPD;UEM) – Department of Agronomy – State University of Maringá