Multiple resistant Euphorbia heterophylla from Paraguay

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

MULTIPLE RESISTANT WILD POINSETTIA
(Euphorbia heterophylla)

Multiple Resistance: 3 Sites of Action
Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase HRAC Group 14 (Legacy E)
Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)

Paraguay, Western

INTRODUCTION		WILD POINSETTIA
Wild Poinsettia (Euphorbia heterophylla) is a dicot weed in the Euphorbiaceae family. In Paraguay this weed first evolved multiple resistance (to 3 herbicide sites of action) in 2026 and infests Soybean. Multiple resistance has evolved to herbicides in the Groups 2 (Legacy B), Inhibition of Protoporphyrinogen Oxidase HRAC Group 14 (Legacy E), and Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G). These particular biotypes are known to have resistance to cloransulam-methyl, fomesafen, glyphosate, and imazethapyr and they may be cross-resistant to other herbicides in the Groups 2 (Legacy B), Inhibition of Protoporphyrinogen Oxidase HRAC Group 14 (Legacy E), and Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G). 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 18, 2026 )
Common Name	Wild Poinsettia
Species	Euphorbia heterophylla
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B) Inhibition of Protoporphyrinogen Oxidase HRAC Group 14 (Legacy E) Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
Herbicides	cloransulam-methyl, fomesafen, glyphosate, and imazethapyr
Location	Paraguay, Western
Year	2026
Situation(s)	Soybean
Contributors - (Alphabetically)	Neumarcio Costa, Marcos Mendoza, and Luiz Zobiole
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Wild Poinsettia biotype with this Wild Poinsettia 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 2, 14, 9 resistant Wild Poinsettia 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 multiple resistant Wild Poinsettia from Paraguay please update the database.

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CONTRIBUTING WEED SCIENTISTS

NEUMARCIO COSTA

Professor and Reseacher Universidade Estadual do Oeste do Paraná Centro de Ciências Agrárias Rua Pernambuco 1,777, Caixa Postal 91 Marechal Cândido Rondon, 85960-128, Paraná Brazil Email Neumarcio Costa

MARCOS MENDOZA

Ingeniero Agronomo Colorado Canindeyu Av Las Residenta FCA, 85960-128, Canindeyu Paraguay Email Marcos Mendoza

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 Paraguay have been instrumental in providing you this information. Particular thanks is given to Neumarcio Costa, Marcos Mendoza, and Luiz Zobiole for providing detailed information.

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Herbicide Resistant Wild Poinsettia Globally
(Euphorbia heterophylla)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Brazil

1993

Soybean

chlorimuron-ethyl, cloransulam-methyl, imazamox, imazaquin, and imazethapyr

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Brazil

2004

Corn (maize), and Soybean

acifluorfen, cloransulam-methyl, diclosulam, flumetsulam, flumiclorac-pentyl, fomesafen, imazethapyr, lactofen, metsulfuron-methyl, nicosulfuron, and saflufenacil

Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)

Brazil

2019

Soybean

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Ecuador

1990

Corn (maize), and Soybean

linuron

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Paraguay

1995

Soybean

imazethapyr

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Paraguay

2026

Soybean

cloransulam-methyl, fomesafen, glyphosate, and imazethapyr

Multiple Resistance: 3 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)
Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Literature about Similar Cases

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Saeid Hassanpour-bourkheili , Mahtab Heravi , Javid Gherekhloo, Ricardo Alcántara-de la Cruz, Rafael De Prado. 2020. Fitness Cost of Imazamox Resistance in Wild Poinsettia (Euphorbia heterophylla L.). Agronomy 10 : 1859 - .

Wild poinsettia (Euphorbia heterophylla L.) is a difficult-to-control weed in soybean production in Brazil that has developed resistance to herbicides, including acetolactate synthase inhibitors. We investigated the potential fitness cost associated to the Ser-653-Asn mutation that confers imazamox resistance in this weed. Plant height, leaf and stem dry weight, leaf area and seed production per plant as well as the growth indices of specific leaf area, leaf area ratio, relative growth rate and net assimilation in F2 homozygous resistant (R) and susceptible (S) wild poinsettia progenies were pairwise compared. S plants were superior in most of the traits studied. Plant heights for S and R biotypes, recorded at 95 days after planting (DAP), were 137 and 120 cm, respectively. Leaf areas were 742 and 1048 cm2 in the R and S biotypes, respectively. The dry weights of leaves and stems in the S plants were 30 and 35%, respectively, higher than in the R plants. In both biotypes, the leaves had a greater share in dry weight at early development stages, but from 50 DAP, the stem became the main contributor to the dry weight of the shoots. The R biotype produced 110 ± 4 seed plant−1 , i.e., 12 ± 3% less seeds per plant than that of the S one (125 ± 7 seed plant−1 ). The growth indices leaf area ratio and specific leaf area were generally higher in the S biotype or similar between both biotypes; while the relative growth rate and net assimilation rate were punctually superior in the R biotype. These results demonstrate that the Ser-653-Asn mutation imposed a fitness cost in imazamox R wild poinsettia..

Lopes Ovejero, R. F. ; Soares, D. J. ; Oliveira, W. S. ; Fonseca, L. B. ; Berger, G. U. ; Soteres, J. K. ; Christoffoleti, P. J.. 2013. Residual herbicides in weed management for glyphosate-resistant soybean in Brazil. Planta Daninha 31 : 947 - 959.

In agricultural production systems where the glyphosate-resistant soybean crop (Glycine max) is grown and the practice of crop rotation with alternative herbicides is not adopted, the exclusive and continuous use of glyphosate has led to the occurrence of resistant weed populations that may limit or compromise the benefits of this technology. Thus, the efficacy of weed management programs, including the use of residual herbicides (sulfentrazone, flumioxazin, imazethapyr, diclosulan, chlorimuron and s-metolachlor) applied in preemergence and followed by in-crop postemergence applications of glyphosate (PRE-POST) were compared to glyphosate postemergence only programs - POST. The study was conducted across nine locations during the 2009/2010 and 2010/2011 growing seasons. PRE-POST programs were efficient in the control of Amaranthus viridis, Brachiaria plantaginea, Bidens pilosa, Commelina benghalensis, Eleusine indica, Euphorbia heterophylla and Raphanus raphanistrum, with the level of control being similar when comparing the program with two applications of glyphosate POST. Some PRE-POST programs were not efficient in controlling Cenchrus echinatus, Ipomoea hederifolia and Ipomoea triloba. Sulfentrazone and diclosulam PRE-POST programs improved the control of Ipomoea triloba compared to sequential applications of glyphosate alone. No significant differences in soybean yield were observed between any of the herbicide treatments or study locations. The use of residual herbicides in preemergence followed by glyphosate in-crop postemergence provides consistent weed control and reducing early season weed competition. Furthermore, these programs utilize at least two herbicide modes of action for herbicide use diversity, which will be needed to stay ahead of resistance build-up, regardless of when weeds may appear..

Vargas, L. ; Nohatto, M. A. ; Agostinetto, D. ; Bianchi, M. A. ; Paula, J. M. ; Polidoro, E. ; Toledo, R. E.. 2013. Management practices × Euphorbia heterophylla resistance to ALS-inhibitors and tolerance to glyphosate in Rio Grande do Sul. Planta Daninha 31 : 427 - 432.

The intensive use of glyphosate in Roundup Ready® (RR) soybean fields in Rio Grande do Sul (RS), in recent years may have selected wild poinsettia (Euphorbia heterophylla) biotypes resistant to the herbicide. This scenario will further complicate the management of this species, since evidence remains of the presence of herbicide resistant biotypes also in acetolactate synthase (ALS)-inhibitors. Thus, the objectives of this work were to evaluate wild poinsettia's sensitivity to the ALS-inhibiting herbicides and glyphosate; to investigate the distribution of resistant biotypes in the state of RS;and to determine the main agronomic factors associated with control failures. Seeds of wild poinsettia plants that survived glyphosate applications were collected from RR soybean fields located in 56 municipalities in the state of RS. On the occasion, the farmers were interviewed through a questionnaire aiming to collect information on the management of the area. Using the seeds collected, two experiments were conducted under greenhouse conditions. The first evaluated the response of 86 biotypes to glyphosate, applied at the rate of 2.160 g ha^-1 while the second experiment evaluated the response of the herbicide imazethapyr to 73 biotypes, applied at a dose of 200 g a.i. ha^-1. The results show that all the wild poinsettia biotypes evaluated are susceptible to glyphosate, but some are resistant to ALS-inhibitors. The survey responses indicate that management practices such as the use of sub doses and/or intensive use of glyphosate, as well as lack of crop rotation favor failures in wild poinsettia control by glyphosate in soybean..

Braz, G. B. P. ; Oliveira Júnior, R. S. de ; Constantin, J. ; Dan, H. de A. ; Oliveira Neto, A. M. de ; Santos, G. ; Constantin, A. F. ; Takano, H. K.. 2011. Alternative herbicides for controlling Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitor in cotton crop. Revista Brasileira de Herbicidas 10 : .

The presence of Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitors is a problem to weed management in cotton crop, due to the fact that few alternatives broadleaf selective herbicides area available. In order to supply this information gap, four experiments were established in greenhouse conditions with the objective of evaluating herbicides applied in post-emergence conditions, recommended either for conventional and transgenic cotton (resistant to glyphosate and amonio-glufosinate) for controlling these resistant biotypes. The experimental design was entirely randomized with four replications and 21 herbicides treatments, besides a check without herbicide application. Two experiments were conducted per species, where the first one corresponded to herbicides application in stages of two to four leaves, and the second in the stage of four to six. It was evaluated the percentage of control at 7 and 28 days after herbicide application. Amonio-glufosinate and glyphosate applied isolated or in combinations with other herbicides were effective in controlling B. pilosa independently of the growth stage. The two biotypes demonstrated to be highly resistant to ALS inhibitor herbicides. E. heterophylla showed greater sensitivity to herbicide amonio-glufosinate herbicide and glyphosate in early stages applications. Glyphosate stood out as a satisfactory alternative for controlling E. heterophylla. For this biotype, synergistic effect was verified for associations between amonio-glufosinate and pyrithiobac-sodium..

Vargas, L. ; Nohatto, M. A. ; Agostinetto, D. ; Bianchi, M. A. ; Gonçalves, E. M. ; Toledo, R. E.. 2011. Response of Euphorbia heterophylla biotypes to glyphosate rates. Planta Daninha 29 : 1121 - 1128.

Wild poinsettia is an annual cycle weed, commonly found in soybean crop in southern Brazil. It is controlled by glyphosate in genetically-modified soybean (Roundup Ready®-RR). The control of this species has not proven to be satisfactory in some places in the last years, leading to the suspicion that biotypes resistant to glyphosate have been selected. The objective this work was to evaluate, by response-dose curve, wild poinsettia biotypes with suspected resistance to glyphosate. The experiment was conducted under greenhouse conditions and the experiment was arranged in a randomized complete block design, with four replications. The treatments consisted of increased application rates of glyphosate (0, 90, 180, 360, 720, 1,080, 1,440 and 2,160 g a.e. ha^-1) on five wild poinsettia biotypes, from crop soybean RR in the state of Rio Grande do Sul. Control and dry weight were evaluated. The results indicated that the wild poinsettia biotypes are susceptible to glyphosate..

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