Bioscience Journal  |  2022  |  vol. 38, e38018  |  ISSN 1981-3163 
 

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Maria Renata Rocha PEREIRA1 , Sidnei MARCHI2 , Dagoberto MARTINS3  
 
1 Department of Forestry, Technology College of the State of São Paulo - Capão Bonito, Capão Bonito, São Paulo, Brazil.  
2 Department of Agronomy, State University of Mato Grosso, Barra do Garças, Mato Grosso, Brazil.  
3 Department of Plant Science, São Paulo State University, Jaboticabal, São Paulo, Brazil. 

 
Corresponding author: 
Maria Renata Rocha Pereira 
Email: maria.pereira30@fatec.sp.gov.br 
 
How to cite: PEREIRA, M.R.R., MARCHI, S. and MARTINS, D. Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes 
resistant to ALS inhibitors. Bioscience Journal. 2022, 38, e38018. https://doi.org/10.14393/BJ-v38n0a2022-53823 

 
Abstract 
Select herbicides with different mechanism of action is a satisfactory option for resistant weed control. Then, 
the present work aimed to study the efficiency of different herbicides and their mixtures on Bidens pilosa 
(blackjack) and Euphorbia heterophylla (wild poinsettia) biotypes, resistant to ALS herbicides in two 
development stages. The trials we arranged in a completely randomized design with four replications. The 
treatments tested were (g a.i/a.e ha-1): imazethapyr at 70 and 140 (WG formulation) + 1.0% Assist; 
imazethapyr at 57.6 and 72 (SL formulation) + 1.0% Assist; imazapic + imazethapyr at 56 and 70 + 1.0% Assist; 
glyphosate + imazethapyr (596); saflufenacil + glyphosate at 35 + 720 + 0.5% Dash in tank mix, glyphosate at 
720 and, a control without herbicide application. Control efficiency was evaluated, as well as dry matter 
accumulation at the end of the studies. Plants of both species were more susceptible to herbicides at the 
early stage of development (2 to 4 leaves). The treatments with saflufenacil + glyphosate, (imazethapyr + 
glyphosate) and glyphosate promoted the best controls, regardless of the species studied and the application 
stage. The mixture with saflufenacil provided the highest control speed, and the mixture (imazethapyr + 
glyphosate) was less efficient among three excellent treatments when applied to plants in the 4-6 leaf stage. 
The treatments (imazethapyr, in both formulations) and (imazethapyr + imazapic) were ineffective in 
controlling the studied biotypes, regardless of dose and developmental stage studied. 
 
Keywords: Acetolactate Synthase. Blackjack. Resistance. Wild Poinsettia. 
 
1. Introduction 

Currently, weed resistance to herbicides is a major concern of modern agriculture. Forty-three cases 
have already been reported in Brazil, with an average of two confirmed cases of resistance to herbicides per 
year. These data place Brazil in the fifth position in the ranking of countries with the highest number of 
resistance reports (Francischini et al. 2019; Heap 2019). 

ALS-inhibiting herbicides was introduced to the world market in 1982 and are currently the leader in 
resistance cases worldwide, with a record of 159 resistant weed species, which represent 63% of cases 
(Chapinotto et al. 2017; Bonow et al. 2018; Heap 2019). According to Takano et al. (2016), the first report of 
resistance to ALS inhibitors in Bidens pilosa L. was verified in soybean fields in the state of Mato Grosso do 
Sul in 1993. 

Christoffoleti e Nicolai (2016) considered as the main consequences of weed resistance to herbicides 
the unfeasibility of using these products, loss of planting areas, reduced productivity and product quality, 
need for herbicide reapplication, and changes in the production system. 

EFFECT OF DIFFERENT HERBICIDES ON BIDENS PILOSA AND 
EUPHORBIA HETEROPHYLLA BIOTYPES RESISTANT TO ALS 

INHIBITORS 

https://orcid.org/0000-0001-8023-2562
https://orcid.org/0000-0002-2673-5094
https://orcid.org/0000-0002-2346-9667


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Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes resistant to ALS inhibitors 

In a report by Ulguim et al. (2019), for better decision-making in management strategies, one must 
know the factors that influence the pressure when selecting resistant weed biotypes. Among them, the 
adoption of more convenient and economical agricultural practices by producers may lead to the emergence 
of herbicide-resistant biotypes, forcing a change in the adopted practices, which requires close monitoring 
of populations for early and rapid resistance detection, thus avoiding economic losses (Burgos et al. 2013). 

Some strategies can be efficient in the control of persistent weeds, such as the use of herbicides with 
different mechanisms of action, as well as their association, inhibiting the selection of new resistant biotypes 
(Powles and Yu 2010; Oliveira Neto et al. 2010). 

Thus, selecting herbicides with a diverse mechanism of action becomes a satisfactory option for 
resistant weed control together with a management strategy against resistant plant development since a 
broader range of mechanism of action of herbicides is required (Trezzi et al. 2009). 

Recent results of resistant species biotypes have been proven by several researchers, such as 
Chiapinotto et al. (2017), who found high levels of resistance of Cyperus iria L. to ALS-inhibiting herbicides. 
Similarly, Ulguim et al. (2019) observed that almost half of the samples taken in the Rio Grande do Sul from 
plants of the genus Cyperus were resistant to ALS inhibitors probably due to the high pressure of selection 
of resistant biotypes by the consecutive use of Clearfield® technology, application of doses higher than that 
registered, and low crop rotation adoption. Also, Bonow et al. (2018) observed that accessions of 
Echinochloa crus-galli var. mitis (Pursh) Peterm. in paddy fields also showed resistance to ALS-inhibiting 
herbicides, indicating the adoption of herbicides with alternative mechanisms of action, such as EPSPS 
inhibitors (glyphosate). 

Thus, this research aimed to study the efficiency of some herbicides on B. pilosa and E. heterophylla 
biotypes resistant to ALS-inhibiting herbicides. 
 
2. Material and Methods 

The study was conducted under greenhouse conditions, with 2.5-L plastic pots filled with arable soil 
classified as a medium textured Dark Red Latosol. It consisted of four experiments, two per species (B. pilosa 
and E. heterophylla) resistant to ALS-inhibiting herbicides. For each species, herbicides were sprayed at two 
plant development stages (2–4 and 4–6 leaf pairs). 

Treatments were arranged in a completely randomized design with four replications. Each 
experimental plot consisted of a pot with one plant per species. Treatments are shown in Table 1. 
 
Table 1. Doses and herbicides tested in the control of Bidens pilosa and Euphorbia heterophylla plants. 

Treatments Dose (g a.i/a.e ha-1) 
1. Control - 
2. imazethapyr1 + Assist 70.0 + 1.0% v/v 
3. imazethapyr1 + Assist 140.0 + 1.0% v/v 
4. imazethapyr2 + Assist 57.6 + 1.0% v/v 
5. imazethapyr2 + Assist 72.0 + 1.0% v/v 
6. (imazapic + imazethapyr)3 + Assist 14.0 + 42.0 + 1.0% v/v 
7. (imazapic + imazethapyr)3 + Assist 17.5 + 52.5 + 1.0% v/v 
8. (glyphosate + imazethapyr)4 509.9 + 86.0 
9. saflufenacil5 + glyphosate6 + Dash 35.0 + 720.0 + 0.5% v/v 

10. Glyphosate 720.0 
1Pivot DG; 2Pivot 100 SL; 3Only; 4Alteza; 5Heat; 6Roundup Original; Assist and Dash = mineral oil/adjuvant. 

 
The application was carried out using an air-pressurized stationary sprayer with a constant pressure 

of 200 kPa equipped with a boom with four Teejet XR 110.02VS flat fan spray tips, with a spacing of 0.5 m 
between them. The sprayer boom was displaced at a speed of 1 m s−1, which resulted in a spray solution 
consumption of 200 L ha−1. 

Control efficiency of hairy beggarticks and wild poinsettia plants was evaluated at 1, 3, 7, 14, and 21 
days after application (DAA) based on phytointoxication symptoms and using a scoring scale from 0 to 100%, 
where 0% represents the total absence of injury and 100% means plant death (SBCPD 1995). At the end of 



Bioscience Journal  |  2022  |  vol. 38, e38018  |  https://doi.org/10.14393/BJ-v38n0a2022-53823 

 
 
 

 
 

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PEREIRA, M.R.R., MARCHI, S. and MARTINS, D. 

the studies, plants of both species remaining in the pots were collected to determine their dry matter.  
The results were subjected to analysis of variance by the F-test and means compared by the Tukey 

test at 5% probability level. The analysis of variance and comparison of means was performed by the 
program SISVAR. 
 
3. Results and Discussion 

Table 2 shows that the mixture of herbicides saflufenacil + glyphosate + Dash (Treatment 9) was the 
only treatment that provided injuries to B. pilosa plants at the stage of 2 to 4 leaf pairs at 1 DAA, reaching 
71.5% control, which is considered good control. All herbicides and doses provided some intoxication effect 
on hairy beggarticks plants at 3 DAA, and the mixture contained in Treatment 9 reached an excellent control 
(97.5%) and all other treatments showed unsatisfactory controls. 

Some treatments reduced and others increased the control at 7 DAA, such as imazethapyr + Assist at 
the two tested doses (Treatments 2 and 3), which provided low control increases, as well as Treatments 8 
(glyphosate + imazethapyr) and 10 (glyphosate) applied alone, which had controls of 47.5 and 65%, 
respectively. Moreover, Treatment 9 (saflufenacil + glyphosate + Dash) provided the death (100%) of hairy 
beggarticks plants resistant to ALS inhibitors (Table 2). 

The behavior of the different treatments tested at 14 DAA when compared to the control of B. pilosa 
plants was more explicit and consistent. The application of Treatments 8 (glyphosate + imazethapyr) and 10 
(glyphosate) also resulted in the death of 100% of the plants, as reported for the mixture saflufenacil + 
glyphosate + Dash. Treatments 2 and 3 with imazethapyr + Assist in the two tested doses presented small 
increases and were still considered unsatisfactory. Also, Treatments 4 and 5 (imazethapyr + Assist) and 6 and 
7 (imazethapyr + imazapic) + Assist were ineffective in controlling hairy beggarticks plants regardless of the 
dose, with the initial injuries disappearing completely. Monqueiro and Christoffoleti (2000) tested different 
herbicides on B. pilosa and B. subalternans DC. plants and observed that ALS-inhibiting herbicides were not 
efficient when applied alone or in mixture with each other. However, a satisfactory control was found in 
populations when a mixture of ALS-inhibiting herbicides was applied with alternative herbicides, making the 
control efficient in both susceptible and resistant populations, which corroborates the results obtained in 
the present study with Treatments 8, 9, and 10 (Table 2). 

At the end of the study (21 DAA), only treatments with glyphosate (8, 9, and 10) provided control of 
hairy beggarticks plants, while treatments with imazethapyr (2 and 3) presented small injuries (Table 2). The 
lowest dry matter accumulations were also observed in these treatments. Treatments 4, 5, 6, and 7 still 
provided no injury to B. pilosa plants during this period, showing the biotype resistance to ALS-inhibiting 
herbicides, as well as to the two doses of imazethapyr + Assist (Treatments 2 and 3). 

Bonow et al. (2018) observed that the application of ALS-inhibiting herbicides was not efficient in 
controlling resistant biotypes, recommending the adoption of products with alternative mechanisms of 
action such as ACCase inhibitors (cialofop-butyl, profoxidime and cletodime), glyphosate and propanil, 
corroborating the results found here. 
 
Table 2. Effect of chemical treatments on the percentage of visual control and dry matter accumulation in 
Bidens pilosa plants at the stage of 2 to 4 leaf pairs during different evaluation periods after herbicide 
application. 

Treatments 
Dose (g 
a.i/a.e 
ha-1) 

Days After Application (DAA) Dry 
Matter 

(g-1) 
1 3 7 14 21 

1. control - 0.0B 0.0E 0.0E 0.0C 0.0C 4.0A 
2. imazethapyr1 + 

Assist 
70.0 + 

1.0% v/v 
0.0B 2.5CD 4.7D 8.0B 5.5B 1.6BC 

3. imazethapyr1 + 
Assist 

140.0 + 
1.0% v/v 

0.0B 2.5CD 6.2D 6.5B 5.0B 1.4BC 

4. imazethapyr2 + 
Assist 

57.6 + 
1.0% v/v 

0.0B 2.0DE 2.5DE 0.0C 0.0C 2.0B 



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Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes resistant to ALS inhibitors 

5. imazethapyr2 + 
Assist 

72.0 + 
1.0% v/v 

0.0B 3.2BCD 2.0DE 0.0C 0.0C 2.6AB 

6. (imazapic + 
imazethapyr)3 + 

Assist 

14.0 + 
42.0 + 

1.0% v/v 
0.0B 3.0BCD 2.7DE 0.0C 0.0C 2.5AB 

7. (imazapic + 
imazethapyr)3 + 

Assist 

17.5 + 
52.5 + 

1.0% v/v 
0.0B 3.2BCD 2.7DE 0.0C 0.0C 1.9B 

8. (glyphosate + 
imazethapyr)4 

509.9 + 
86.0 

0.0B 4.5BC 47.5C 100A 100A 0.0C 

9. saflufenacil5 + 
glyphosate6 + 

Dash 

35.0 + 
720.0 + 

0.5% v/v 
71.5A 97.5A 100A 100A 100A 0.0C 

10. glyphosate 720.0 0.0B 4.7B 65.0B 100A 100A 0.0C 
F treatments 608.65** 839.93** 359.76** 485.70** 729.89** 13.64** 

CV (%) 10.53 6.99 8.16 5.11 1.02 44.42 
LSD 1.82 2.08 4.60 3.88 0.76 1.71 

1Pivot DG; 2Pivot 100 SL; 3Only; 4Alteza; 5Heat; 6Roundup Original; Assist and Dash = mineral oil/adjuvant. **Significant at 1% 
probability. Means followed by the same letter in the column do not differ statistically from each other by the Tukey test (p>0.05). 

 
Table 3 shows that some herbicides had already caused intoxication to the most developed B. pilosa 

plants (4 to 6 leaf pairs) at 1 DAA, especially the mixture saflufenacil + glyphosate + Dash (Treatment 9), with 
a 42% control, but lower than that found when plants had 2 to 4 leaf pairs (Table 2), which reached 71.5% 
control during this same period. Some treatments showed an evolution in the control at 3 DAA, but still 
unsatisfactory, standing out the Treatment 9, with 83.2% control. 

At 7 DAA, chemical treatments behaved similarly to those applied in the first tested stage (2 to 4 leaf 
pairs), but with lower controls (Table 3). A continuous increased control of Bidens pilosa plants was also 
observed in some treatments at 14 DAA, such as Treatments 8 (imazethapyr + glyphosate), 9 (saflufenacil + 
glyphosate + Dash), and 10 (glyphosate), with 66.2, 100, and 94.5% control, respectively, besides showing 
that the mixture of imazethapyr + glyphosate had an inferior behavior when compared to the isolated 
application of glyphosate. The mixture of saflufenacil + glyphosate + Dash led to the death of hairy 
beggarticks plants only at 14 DAA, unlike at the stage of 2 to 4 leaf pairs, in which plant death occurred at 7 
DAA (Table 2). It shows that adequate management of the mechanism of action of herbicides, coupled with 
the correct plant development stage for the application, provides more efficient control over weeds, 
especially for resistant biotypes. These results corroborate those observed by Braz et al. (2011), when they 
applied glyphosate to control resistant biotypes in a GR cotton crop, proving to be a viable alternative to 
ALS-inhibiting herbicides. 

An increase in the control of B. pilosa plants in relation to the previous evaluation was observed at 
21 DAA for treatments with imazethapyr + glyphosate and glyphosate, with 90 and 99.5% control, 
respectively, while the mixture saflufenacil + glyphosate + Dash reached 100% control. However, the mixture 
of imazethapyr + glyphosate provided a lower control at this more advanced stage of plant development (4 
to 6 leaves). Table 3 also shows that dry matter accumulation in the plants was significantly lower in 
treatments that visually presented the best controls (Treatments 8, 9, and 10). The use of herbicides with 
different mechanism of action or combined with ALS-inhibiting herbicides has become an alternative for the 
control of resistant B. pilosa plants since herbicides such as imazethapyr stand out for their efficient control 
over other weed species, such as Setaria spp., Chenopodium album L., Solanum spp., Amaranthus retroflexus 
L., and Digitaria sanguinalis (L.) Scop (Alister and Kogan 2005). 

All treatments with imazethapyr + Assist (Treatments 2 and 3), imazethapyr + Assist (Treatments 4 
and 5), and imazethapyr + imazapic + Assist (Treatments 7 and 8) were not effective in controlling B. pilosa 
plants at the stage of 4 to 6 leaf pairs, showing the resistance of the biotype to the group of ALS-inhibiting 
herbicides (Table 3). Takano et al. (2016) worked with dose-response curves of the herbicide imazethapyr 
on resistant and susceptible B. pilosa biotypes and found that the resistant biotype was not controlled even 
at high doses (800 g ha−1), which is ≈ 8x the recommended dose, with control lower than 50%. 



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PEREIRA, M.R.R., MARCHI, S. and MARTINS, D. 

Table 3. Effect of chemical treatments on the percentage of visual control and dry matter accumulation in 
Bidens pilosa plants at the stage of 4 to 6 leaf pairs during different evaluation periods after herbicide 
application. 

Treatments 
Dose (g 

a.i/a.e ha-
1) 

Days After Application (DAA) Dry 
Matter 

(g-1) 
1 3 7 14 21 

1. control - 0.0B 0.0C 0.0D 0.0C 0.0C 6.96A 
2. imazethapyr1 + 

Assist 
70.0 + 

1.0% v/v 
0.0B 0.0C 0.0D 0.0D 0.0C 7.47A 

3. imazethapyr1 + 
Assist 

140.0 + 
1.0% v/v 

0.0B 0.0C 4.2D 0.0D 0.0C 7.96A 

4. imazethapyr2 + 
Assist 

57.6 + 
1.0% v/v 

0.0B 2.7B 5.2D 0.0D 0.0C 6.61A 

5. imazethapyr2 + 
Assist 

72.0 + 
1.0% v/v 

0.0B 0.0BC 4.2D 0.0D 0.0C 6.07A 

6. (imazapic + 
imazethapyr)3 + 

Assist 

14.0 + 
42.0 + 

1.0% v/v 
0.0B 0.0C 2.2D 7.5C 0.0C 5.40AB 

7. (imazapic + 
imazethapyr)3 + 

Assist 

17.5 + 
52.5 + 

1.0% v/v 
0.0B 9.7C 1.0D 3.0C 0.0C 5.85A 

8. (glyphosate + 
imazethapyr)4 

509.9 + 
86.0 

0.0B 97.5B 14.7C 66.2B 90.0B 2.23BC 

9. saflufenacil5 + 
glyphosate6 + Dash 

35.0 + 
720.0 + 

0.5% v/v 
85.0B 100A 98.5A 100A 100A 0.92C 

10. glyphosate 720.0 0.0B 97.5B 30.0B 94.5A 99.5A 0.92C 
F treatments 1734.00** 995.48** 639.67** 932.08** 319.25** 3.80** 

CV (%) 15.19 8.42 14.97 10.22 8.54 28.56 
LSD 3.11 6.84 5.81 6.69 6.13 3.47 

1Pivot DG; 2Pivot 100 SL; 3Only; 4Alteza; 5Heat; 6Roundup Original; Assist and Dash = mineral oil/adjuvant. **Significant at 1% 
probability. Means followed by the same letter in the column do not differ statistically from each other by the Tukey test (p>0.05). 

 
Table 4 shows that the mixture of saflufenacil + glyphosate + Dash was the only chemical treatment 

that caused damage to E. heterophylla plants (2 to 4 leaf pairs) at 1 DAA, reaching 85% control. The mixture 
of saflufenacil + glyphosate + Dash increased the control over wild poinsettia plants at 3 DAA, reaching 
96.2%. On the other hand, Treatments 8 (imazethapyr + glyphosate) and 10 (glyphosate) presented controls 
of the order of 30%, and the others did not provide visual injuries during this period (Table 4). 

Most chemical treatments provided some toxic effect to E. heterophylla plants at 7 DAA and showed 
evolution in their control, except for the application of Treatment 6 (imazethapyr + imazapic + Assist) at the 
lowest dose. The mixture of herbicides of Treatment 9 (saflufenacil + glyphosate + Dash) resulted in the 
death of wild poinsettia plants during this period (100%), while Treatments 8 (imazethapyr + glyphosate) 
and 10 (glyphosate) provided a similar and efficient control, with a value of 97.5% (Table 4). All other 
treatments and doses provided unsatisfactory controls, which proves the resistance of this biotype of E. 
heterophylla to ALS-inhibiting herbicides. Similarly, Chiapinotto et al. (2017) worked with dose-response to 
confirm resistance in biotypes of C. iria and found the existence of resistant biotypes to ALS-inhibiting 
herbicides, as the control level and dry matter reduction was lower and gradual when compared to those of 
the susceptible biotype. According to these researchers, the emergence of resistance necessarily occurs due 
to a change in the structure of the ALS enzyme and its site of action, caused by a mutation in the gene 
(Ntoanidou et al. 2016). 

Most chemical treatments showed decreases in the control of E. heterophylla plants at 14 DAA, 
except for Treatments 8 (imazethapyr + glyphosate) and 10 (glyphosate), which provided a 100% control of 
wild poinsettia plants (Table 4), as in Treatment 9 (saflufenacil + glyphosate + Dash).  



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Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes resistant to ALS inhibitors 

At the end of the study (21 DAA), treatments with persistent visual intoxication symptoms slowed 
these effects, which also allowed weed recovery, except for treatments with glyphosate, which had already 
reached 100% control. Dry matter accumulation in plants of E. heterophylla was null in treatments with 
glyphosate (8, 9, and 10), while the other treatments were similar to the control without herbicide 
application (Table 4). Monqueiro and Christoffoleti (2000) observed that E. heterophylla biotypes resistant 
to ALS-inhibiting herbicides were efficiently controlled by Protox-, GS-, and EPSEs-inhibiting herbicides, 
which could be used to minimize the selection effects and manage the resistant population of E. 
heterophylla, as observed. These results showed that the tested biotype was susceptible to the mixture of 
saflufenacil + glyphosate + Dash and herbicides imazethapyr + glyphosate and glyphosate applied alone at 
this early development stage, as they have another mechanism of action. All other treatments with 
imazethapyr + Assist and imazethapyr + imazapic + Assist were ineffective in controlling E. heterophylla 
biotype regardless of the dose and formulation. 
 
Table 4. Effect of chemical treatments on the percentage of visual control and dry matter accumulation in 
Euphorbia heterophylla, plants at the stage of 2 to 4 leaf pairs during different evaluation periods after 
herbicide application. 

Treatments 
Dose (g 

a.i/a.e ha-1) 

Days After Application (DAA) Dry 
Matter 

(g-1) 
1 3 7 14 21 

1. control - 0.0B 0.0C 0.0C 0.0D 0.0C 3.73A 
2. imazethapyr1 + 

Assist 
70.0 + 1.0% 

v/v 
0.0B 0.0C 7.5B 7.0BC 0.0C 4.12A 

3. imazethapyr1 + 
Assist 

140.0 + 
1.0% v/v 

0.0B 0.0C 11.2B 6.0BC 0.0C 4.41A 

4. imazethapyr2 + 
Assist 

57.6 + 1.0% 
v/v 

0.0B 0.0C 8.5B 8.7B 1.2BC 3.86A 

5. imazethapyr2 + 
Assist 

72.0 + 1.0% 
v/v 

0.0B 0.0C 5.0BC 3.0CD 2.2BC 4.03A 

6. (imazapic + 
imazethapyr)3 + Assist 

14.0 + 42.0 
+ 1.0% v/v 

0.0B 0.0C 0.0C 0.0D 0.0C 2.78AB 

7. (imazapic + 
imazethapyr)3 + Assist 

17.5 + 52.5 
+ 1.0% v/v 

0.0B 0.0C 9.7B 6.7BC 3.2B 2.68AB 

8. (glyphosate + 
imazethapyr)4 

509.9 + 86.0 0.0B 30.0B 97.5A 100A 100A 0.0B 

9. saflufenacil5 + 
glyphosate6 + Dash 

35.0 + 720.0 
+ 0.5% v/v 

85.0A 96.2A 100A 100A 100A 0.0B 

10. glyphosate 720.0 0.0B 30.0B 97.5A 100A 100A 0.0B 
F treatments 734.55** 153.90 995.48** 229.18** 503.39** 8.15** 

CV (%) 15.19 30.99 8.42 5.82 3.87 50.59 
LSD 3.11 11.96 6.84 4.65 2.87 3.13 

1Pivot DG; 2Pivot 100 SL; 3Only; 4Alteza; 5Heat; 6Roundup Original; Assist and Dash = mineral oil/adjuvant. **Significant at 1% 
probability. Means followed by the same letter in the column do not differ statistically from each other by the Tukey test (p>0.05). 

 
The effect of different chemical treatments on E. heterophylla plants at the stage of 4 to 6 leaf pairs 

showed that only the mixture saflufenacil + glyphosate + Dash (Treatment 9) caused plant injury to wild 
poinsettia at 1 DAA, but with a very poor control of 18.7% (Table 5), which is much lower than that found at 
the stage of 2 to 4 leaf pairs (85%) (Table 4). All herbicides provided some toxic effect to E. heterophylla 
plants at 3 DAA, except for the treatment with the herbicide imazethapyr + imazapic + Assist (Treatment 6) 
at the lowest dose. Plants treated with the saflufenacil + glyphosate + Dash showed significant control 
increases, reaching a value of 57.5% (Table 5). 

Only the mixture saflufenacil + glyphosate + Dash provided an efficient control of wild poinsettia 
plants at 7 DAA, with a value of 96.7% (Table 5). However, the other chemical treatments were still 
ineffective to control wild poinsettia plants, unlike that observed at the first studied development stage, 



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PEREIRA, M.R.R., MARCHI, S. and MARTINS, D. 

when the mixture of imazethapyr + glyphosate and the isolated application of glyphosate provided efficient 
controls during this period, with a value of 97.7% control for both treatments (Table 4) and 46.2 and 67.5%, 
respectively (Table 5). An increase in control efficiency of some of the tested treatments was observed at 14 
DAA, with only the treatments saflufenacil + glyphosate + Dash, imazethapyr + glyphosate, and glyphosate 
providing controls ranging from good to excellent (99, 82.5, and 97%, respectively) (Table 5). 

Increases in the action of treatments with imazethapyr + glyphosate, saflufenacil + glyphosate + Dash, 
and glyphosate were observed again on E. heterophylla plants at 21 DAA, with values of controls of 88.7, 
100, and 98%, respectively, while the mixture of imazethapyr + glyphosate remained inferior. The high toxic 
visual effects recorded in wild poinsettia plants in these three treatments reflected statistically on dry matter 
accumulation of plants, with lower accumulations when compared to other treatments that did not provide 
efficient control of plants (Table 5). 

These results showed that the tested biotype was susceptible to Treatments 8, 9, and 10, as observed 
for the development stage of 2 to 4 leaf pairs (Table 4). However, a lower action of these treatments was 
evidenced at the stage of 4 to 6 leaf pairs, but the mixture saflufenacil + glyphosate + Dash showed a total 
control (Table 5), evidencing the importance of the rotation of herbicides of different mechanisms of action. 
In this sense, Vargas et al. (2013) studied plants of E. heterophylla resistant to ALS inhibitors and observed 
an efficient control with glyphosate application. This research highlighted the importance of using crop 
rotation to prevent the selection of resistant biotypes, mixtures of herbicides with different mechanisms of 
action as a strategy to avoid resistance to herbicides, and constant monitoring of the occurrence of plant 
escape. 

All treatments with imazethapyr + Assist and imazethapyr + imazapic + Assist were ineffective in 
controlling E. heterophylla plants at the stage of 4 to 6 leaf pairs (Table 5), which corroborates the results 
obtained by Aarestrup et al. (2008), who verified that a resistant biotype of E. heterophylla was not 
controlled by another ALS-inhibiting herbicide (chlorimuron-ethyl). 
 
Table 5. Effect of chemical treatments on the percentage of visual control and dry matter accumulation in 
Euphorbia heterophylla, plants at the stage of 4 to 6 leaf pairs during different evaluation periods after 
herbicide application. 

Treatments 
Dose (g 

a.i/a.e ha-1) 

Days After Application (DAA) Dry 
Matter 

(g-1) 
1 3 7 14 21 

1. control - 0.0B 0.0B 0.0C 0.0C 0.0C 6.00A 
2. imazethapyr1 + 

Assist 
70.0 + 1.0% 

v/v 
0.0B 0.7B 0.7C 0.0C 0.0C 5.52A 

3. imazethapyr1 + 
Assist 

140.0 + 
1.0% v/v 

0.0B 0.0B 0.0C 0.0C 0.0C 6.50A 

4. imazethapyr2 + 
Assist 

57.6 + 1.0% 
v/v 

0.0B 0.7B 2.5B 1.2C 0.0C 6.00A 

5. imazethapyr2 + 
Assist 

72.0 + 1.0% 
v/v 

0.0B 0.5B 6.2C 3.7C 1.7C 5.00A 

6. (imazapic + 
imazethapyr)3 + Assist 

14.0 + 42.0 
+ 1.0% v/v 

0.0B 0.0B 0.0C 0.0C 0.0C 6.75A 

7. (imazapic + 
imazethapyr)3 + Assist 

17.5 + 52.5 
+ 1.0% v/v 

0.0B 0.7B 1.0C 0.0C 0.0C 4.75A 

8. (glyphosate + 
imazethapyr)4 

509.9 + 
86.0 

0.0B 0.7B 46.2B 82.5B 88.7B 2.50B 

9. saflufenacil5 + 
glyphosate6 + Dash 

35.0 + 
720.0 + 

0.5% v/v 
18.7A 57.5A 96.7A 99.0A 100A 3.15B 

10. glyphosate 720.0 0.0B 1.7B 67.5B 97.0A 98.0A 3.00B 
F treatments 61.36** 134.46 63.62** 512.12** 538.00** 2.16** 

CV (%) 80.74 49.05 39.74 13.94 4.75 32.85 
LSD 3.65 7.48 21.31 9.53 3.31 3.28 



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8 

Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes resistant to ALS inhibitors 

1Pivot DG; 2Pivot 100 SL; 3Only; 4Alteza; 5Heat; 6Roundup Original; Assist and Dash = mineral oil/adjuvant. **Significant at 1% 
probability. Means followed by the same letter in the column do not differ statistically from each other by the Tukey test (p>0.05). 

 
4. Conclusions 

Plants of both species were more susceptible to herbicides at the early development stage (2 to 4 
leaves). Treatments with saflufenacil + glyphosate + Dash, imazethapyr + glyphosate, and glyphosate 
promoted the best controls regardless of the species and application stage, and the mixture with saflufenacil 
provided the highest control rate; the mixture imazethapyr + glyphosate was less efficient among the best 
treatments when applied to plants of both species at the stage of 4 to 6 leaves; and the treatments 
imazethapyr + Assist (both formulations) and imazethapyr + imazapic + Assist were ineffective in controlling 
the studied biotypes regardless of the dose and stage of development. 
 
Authors' Contributions: PEREIRA, M.R.R.: conception and design, acquisition of data, analysis and interpretation of data, drafting the article; 
MARCHI, S.R.: acquisition of data, analysis and interpretation of data, critical review of important intellectual content; MARTINS, D.: conception 
and design, acquisition of data, analysis and interpretation of data, critical review of important intellectual content. All authors have read and 
approved the final version of the manuscript. 
 
Conflicts of Interest: The authors declare no conflicts of interest. 
 
Ethics Approval: Not applicable. 
 
Acknowledgments: Not applicable. 
 

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Received: 15 April 2020 | Accepted: 11 September 2021 | Published: 31 March 2022 

 

 

  

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