<b>HRAC Group 1</b> <font size='2'> (Legacy A) </font> resistant Digitaria nuda from Brazil

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 1 (LEGACY A) RESISTANT NAKED CRABGRASS
(Digitaria nuda)

Inhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)

Brazil, Rio Verde-GO

INTRODUCTION		NAKED CRABGRASS
Naked Crabgrass (Digitaria nuda) is a monocot weed in the Poaceae family. In Brazil this weed first evolved resistance to Group 1 (Legacy A) herbicides in 2021 and infests Soybean. Group 1 (Legacy A) herbicides are known as Inhibition of Acetyl CoA Carboxylase (Inhibition of Acetyl CoA Carboxylase ). Research has shown that these particular biotypes are resistant to haloxyfop-methyl and they may be cross-resistant to other Group 1 (Legacy A) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Apr 23, 2026 )
Common Name	Naked Crabgrass
Species	Digitaria nuda
Group	Inhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)
Herbicides	haloxyfop-methyl
Location	Brazil, Rio Verde-GO
Year	2021
Situation(s)	Soybean
Contributors - (Alphabetically)	Diego Carvalho, Lucas Rafael de Marco, Andre Dias , Gabriel Rohrer Pereira, Caio Rossi, and Luiz Zobiole
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Naked Crabgrass biotype with this Naked Crabgrass biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 1 resistant Naked Crabgrass have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 1 (Legacy A) resistant Naked Crabgrass from Brazil please update the database.

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CONTRIBUTING WEED SCIENTISTS

DIEGO CARVALHO

Field Researcher ADAMA Brasil R&D Rua RC 02 Q 9, Lt 4 Rio Verde , 75909-302, Goiás Brazil Email Diego Carvalho

LUCAS RAFAEL DE MARCO

Field Scientist Corteva Agriscience Crop Protecrion R&D Rua Providence 00 Uberlandia, 38407744, Minas Gerais Brazil Email Lucas Rafael de Marco

ANDRE DIAS

Research Assistant UPL R&D Rodovia Floriano de Camargo Barros SP-143 Pereiras , 38407744, São Paulo Brazil Email Andre Dias

GABRIEL ROHRER PEREIRA

Field Scientist Corteva Agriscience Crop Health R&D Rod SP-147 km 71 s/n, Caixa Postal: 226, São Paulo, 13801-540, Mogi Mirim Brazil Email Gabriel Rohrer Pereira

CAIO ROSSI

Researcher Agronomist Corteva AgriScience IFS R&D AV.Alexandre Ribeiro Guimaraes 315 - apto 301 Uberlândia, 38408-050, MG Brazil Email Caio Rossi

LUIZ ZOBIOLE

Field Scientist Corteva Agriscience™ Agriculture Division of DowDuPont ™ Crop Protection R&D Rod. SP 147 km 71 Mogi Migim, 13800-970 , São Paulo Brazil Email Luiz Zobiole

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Brazil have been instrumental in providing you this information. Particular thanks is given to Diego Carvalho, Lucas Rafael de Marco, Andre Dias , Gabriel Rohrer Pereira, Caio Rossi, and Luiz Zobiole for providing detailed information.

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Herbicide Resistant Naked Crabgrass Globally
(Digitaria nuda)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Brazil

2021

Soybean

haloxyfop-methyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Literature about Similar Cases

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Dias, A. C. R. ; Carvalho, S. J. P. ; Nicolai, M. ; Christoffoleti, P. J.. 2007. Understanding the occurrence of different species of crabgrass (Digitaria spp.) in sugarcane crop. Planta Daninha 25 : 489 - 499.

Digitaria genus includes ~300 plant species, distributed in the tropical and subtropical regions of both hemispheres. Thirteen described species occur in the state of Sao Paulo, Brazil, with visual differentiation being difficult to be made in the fields due to their great morphological similarity: Digitaria nuda, D. ciliaris, D. horizontalis and D. bicornis, popularly known as crabgrass, are weeds commonly found in sugarcane production fields in São Paulo. Cases of cabgrass control failure have been reported by producers, likely related with weed community changes as a result of the selection of some crabgrass species tolerant to herbicides previously recommended for their control. It has been suspected that these selected populations are constituted by different crabgrass species, notably D. nuda, which has higher tolerance levels to some products. Understanding the dynamics of weed species (Digitaria) population and its mechanisms of tolerance to some herbicide groups will help outline management recommendations for these weeds, avoiding or delaying their manifestation. Identifying the species that occur in sugarcane producing areas will promote the correct herbicide choice, according to the infesting species, thus increasing the chances of successful control..

Dias, N. M. P. ; Christoffoleti, P. J. ; Tornisielo, V. L.. 2005. Taxonomic identification of crabgrass species infesting sugarcane crop in São Paulo State and herbicide efficacy to control Digitaria nuda. Bragantia 64 : 389 - 396.

The continuous use of herbicides from the chemical groups triazines and substituted ureas has imposed a selection pression upon tolerant species of crabgrass (Digitaria spp.) in sugarcane plantations, causing the phenomenon of weed species shift, by reducing the populations of susceptible crabgrass species and increasing the proportion of tolerant species of this weed genus. To scientifically elucidate this phenomenon, this research was developed under field conditions in São Paulo, Brazil, with the following objectives: (a) to evaluate the agronomic efficacy of herbicides used in sugarcane crops to control D. nuda and (b) identify Digitaria species selected by herbicides in areas that received repetitive applications. Eight herbicide treatments (ametryne [ametryn], diuron, tebuthiuron, diuron+hexazinone, imazapyr, isoxaflutole, metribuzin and imazapic), applied during pre-emergence, were used, and control percentage was evaluated at 15, 30 and 60 days after herbicide application (DAA). The identification of species of Digitaria population was carried out following analytical identification key, through the observation of plant morphological characteristics. D. nuda was selected by herbicide repetitive applications. D. nuda was controlled in a lower level by diuron, tebuthiuron, diuron+hexazinone, imazapyr and imazapic. However, ametryne, isoxaflutole and metribuzin showed good efficacy to control until 60 DAA..

Dias, N. M. P. ; Pereira, M. R. D. B. ; López-Ovejero, R. F. ; Christoffoleti, P. J. ; Barela, J. F. ; Tornisielo, V. L.. 2005. Population dynamics of Digitaria spp. submitted to selection pressure by herbicides in sugarcane crop. Journal of Environmental Science and Health. Part B, Pesticides, Food Contaminants, and Agricultural Wastes 40 : 21 - 28.

The objective of this research was to study population dynamics of the weed crabgrass, genus Digitaria, submitted to selection pressure by herbicides currently applied in sugarcane crops in Brazil. In the first experiment two crabgrass species (Digitaria nuda and Digitaria ciliaris) and eight herbicide treatments applied in preemergence were used, and control percentage was evaluated at 7, 14, and 21 days after herbicide application (DAA). In the second experiment the level of tolerance through dose-response curve was determined for the species D. nuda and D. ciliaris, to the herbicides imazapyr, tebuthiuron, ametryne, and metribuzin. All the herbicides studied were efficient in controlling D. ciliaris, however, for D. nuda the best results were obtained only with ametryne, metribuzin, and isoxaflutole. The relation (T/S) between the rate required to reduce plant dry biomass (GR₅₀) at 21 DAA of D. nuda and D. ciliaris was 16 for imazapyr and 6.3 for tebuthiuron, showing differential susceptibility of species; however for ametryne the rate T/S of 1.1 showed that D. nuda was not tolerant to this herbicide. For metribuzin, at 1.92 kg a.i. ha^-1, reduction of dry biomass was 80 and 90% to D. nuda and D. ciliaris, respectively. Even being controlled by metribuzin, D. nuda presented a higher level of tolerance to this herbicide, what was confirmed by the relationship T/S 14.4. As general conclusion of the research, it can be stated that the species D. nuda is more tolerant to ALS inhibiting herbicides and substituted urea, when compared with D. ciliaris; probably, D. nuda was selected by repetitive use of these herbicides..

Dias, N. M. P. ; Regitano, J. B. ; Christoffoleti, P. J. ; Tornisielo, V. L.. 2003. Absorption and translocation of the herbicide diuron by susceptible and tolerant species of crabgrass (Digitaria spp.). Planta Daninha 21 : 293 - 300.

The objective of this research was to compare the tolerance of two crabgrass species (Digitaria nuda and D. ciliaris) to diuron and to evaluate whether absorption and/or translocation are involved in the mechanism of tolerance to the herbicide. In order to determine the tolerance of the crabgrass species, plants at the vegetative growth stage of three true leaves were sprayed with different rates of diuron. Dose-response curves were adjusted to plant dry biomatter at 21 days after application. The absorption and translocation studies were conducted using ¹⁴C-diuron, measuring radioactivity in different plant parts at 0, 3, 6, 12, 24 and 48 hours after application. The results were expressed as percentage related to the total radioactivity recovered. The relation (T/S) between the rate required to reduce plant dry matter (GR₅₀) at 21 DAA of the species D. nuda and the GR₅₀ of D. ciliaris was 2.7, showing differential susceptibility of the species. There was no difference in the absorption by the species. Translocation was minimum in both species. It was concluded that differential absorption and/or translocation were not involved in the mechanism of tolerance to diuron present in Digitaria nuda crabgrass species..

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