Goosegrass develops multiple herbicide resistance in Brazil

Goosegrass (Eleusine indica) has developed multiple- and cross-resistance to the herbicides glyphosate, clethodim, and haloxyfop-p-methyl. 

This finding was detected through research conducted in partnership with Embrapa Cerrado (Brazilian Agricultural Research Corporation), MT Foundation, and private companies.

The work was carried out in November 2024 in the western region of the Brazilian state of Bahia, which is known for its strong grain production, especially soybeans. Researchers said the study results raise the alarm and highlight the importance of monitoring and tracking goosegrass control escapes.

A study conducted by Bio Research Center, led by researcher Erich Duarte, analyzed the weed competition caused by the weed and soybean cultivation losses, considering infestation levels between one and 12 plants per square meter. The research concluded that a single Eleusine indica per square meter in soybean crops has the potential to generate losses of 518 kilograms of the oilseed.

Losses are proportional to weed competition levels. With the presence of two plants, the infestation interference on productivity reaches 1,080 kilograms. With 12 plants per square meter, the loss would jump to 3,024 kilograms of soybeans.

"The emergence of populations with multiple resistance has been worsening, and producers are concerned because they have fewer options for efficient products to control goosegrass. Many producers need to use other techniques, such as mechanical methods. However, soil disturbance ends up breaking seed dormancy and stimulating the germination of other weeds," warned Fabiano Rios, an agronomist who works as Market Development for Sumitomo Chemical.

Goosegrass stands out for its rapid growth, potentially reaching a height between 30 and 50 centimeters. This grass presents prostrate and branched growth parallel to the soil, which gives it a competitive advantage. The weed can develop very well in adverse environments, such as field borders and machinery traffic lines, areas where the soil is typically compacted.

The plant has a large energy reserve in its flattened stems, allowing vigorous development and the formation of a dense population in the field. "This is a species considered aggressive and grows even in inhospitable environments. The producer would need to be more attentive and control it more frequently because Eleusine indica has germination that is very distributed throughout the year, which is related to soil moisture. When it rains, there is a high probability of weed germination," Rios said.

Compared to other concerning weeds, Eleusine indica has a lower dispersal capacity. However, high seed production and the ability to adapt to various climatic conditions, especially in warmer regions, are factors that contribute to goosegrass spread.

The resistance of Eleusine indica to herbicides, especially glyphosate, and haloxyfop, became very evident in cotton cultivation areas, where intensive herbicide use increased the selection pressure of this weed. However, with machinery traffic between cultivation areas and control difficulties, infestations are already causing alerts in soybean, corn, and bean crops. Herbicide-resistant goosegrass has been observed in various crops in the Brazilian states of Mato Grosso, Mato Grosso do Sul, and Goiás, besides its presence in areas in western and northwestern Paraná.

Researchers recommend adopting integrated management strategies and prioritizing early management to mitigate goosegrass impacts on cotton, soybean, corn, and bean crops. Rotation of action mechanisms and awareness about the importance of avoiding resistance selection is fundamental to ensuring the longevity of technologies currently available in the market and crop sustainability.

Pre-planting soybean desiccation is very important to reduce seed banks and weed pressure before establishing the commercial crop. Pre-emergent herbicide applications, mainly products formulated with flumioxazin and imazethapyr, provide good preventive control without carryover risk for subsequent crops.

(Editing by Leonardo Gottems, reporter for AgroPages)