Skip to main content

Resistance of flaxleaf fleabane (Conyza bonariensis (L.) Cronquist) to glyphosate



Resistance to glyphosate has been reported in flaxleaf fleabane populations within a number of grain growing areas in southern Queensland and northern New South Wales and other cropping regions across Australia.


To investigate the processes contributing to the evolution and spread of glyphosate-resistant flaxleaf fleabane, the resistant populations tested in dose-response experiments varied in their responses to glyphosate from two to eight times the recommended rate. The different dose responses obtained may indicate different mechanisms of resistance. This can possibly be attributed to an independent evolution of resistance.


The results demonstrate that glyphosate resistance is widespread across Australia and has likely evolved multiple times as well as dispersing by seeds.


Flaxleaf fleabane (Conyza bonariensis) is a summer-growing weed species belonging to the family Asteraceae (Wu, 2009). Flaxleaf fleabane is an important weed species in agriculture and environmental systems worldwide (Randall, 2017) and is distributed broadly over the warmer environments (TERZİOĞLU & ANŞİN, 2001). Flaxleaf fleabane has recently become a serious problem in a number of grain growing areas in southern Queensland, northern New South Wales and other cropping regions across Australia Wu, Walker (Wu et al., 2006); (Walker & Robinson, 2008); Owen, Owen (Owen et al., 2009). The continual application of glyphosate [N-(phosphonomethyl) glycine] for flaxleaf fleabane control has resulted in the evolution of resistance to this herbicide (Walker & Robinson, 2008). The evolution of resistance in numerous weed species worldwide to the commonly used, highly effective, systemic herbicide glyphosate, which is non-selective and wide spectrum, is of particular concern because this herbicide is important for the sustainability of grain cropping in Australia (Wakelin & Preston, 2006). The first report of glyphosate-resistant populations in flaxleaf fleabane was in South Africa in 2003 according to Moreira et al. (Moreira et al., 2007), and since then, populations resistant to glyphosate have been reported in other countries including the USA, Spain, Colombia, and Brazil. McGillion and Storrie (McGillion & Storrie, 2006) reported that flaxleaf fleabane is one of the most common herbicide-resistant weed species overseas. As a result of the use of glyphosate in summer fallow operations, glyphosate-resistant populations of flaxleaf fleabane have begun to appear in Australia, with the first resistant population identified in 2011 (Aves et al., 2017; Walker et al., 2011).

In Australia, a range of responses has been found to glyphosate among populations of flaxleaf fleabane. Walker et al. (Walker et al., 2011) reported that populations from cropping paddocks seem to be more resistant to glyphosate than those from pastures or non-agricultural sites. Glyphosate resistance was initially confirmed in eight populations of flaxleaf fleabane, from northern NSW and southern Queensland in Australia; since then, the number of resistant populations identified has rapidly increased (Walker et al., 2011). However, the evolution of glyphosate resistance in flaxleaf fleabane is poorly understood. The main objective of this study was to determine the extent of flaxleaf fleabane resistance to glyphosate, using a dose-response study.

Material and methods

Plant materials

Fifteen populations of flaxleaf fleabane were collected from roadside survey across Australia by Malone et al. (Malone et al., 2012), (Table 1).

Table 1 Names, locations, and response to glyphosate of 15 populations of flaxleaf fleabane selected for the dose-response experiment

Seed germination and plant growth

Approximately 0.2 g of seeds from each population were sown in separate trays (30 by 20 by 10 cm) containing coca peat soil in a glasshouse. Seeds were sown directly onto the soil surface and uniformly irrigated as required until an appropriate number of seedlings for each population had emerged. For the dose-response experiment, seedlings were transplanted into standard pots (with 15 cm diameter) at a density of five to 12 seedlings/pot. The plants were maintained under usual growing conditions (outdoor as they were planted in March 2012) throughout the growing period and watered with a mist spray once or twice a day as required, until herbicide application as described below.

Herbicide application

Dose-response experiments were performed on 15 populations of flaxleaf fleabane, one susceptible and 14 resistant as highlighted in Table 1. After 4 weeks of germination, when the plants were at six to eight leaf stage, they were treated with glyphosate. The experiments were set up in a randomized complete block design with three replicates and six rates. The doses applied to resistant populations were 0-, 1-, 2-, 4-, 6- and 8-fold of field rate (field rate 750 g a.i. ha−1), while to the susceptible population, doses applied were 0-, 0.25-, 0.5-, 1-, 2- and 4-fold of field rate of glyphosate (touchdown high tech 500 g/L Monsanto, Melbourne, Victoria, Australia). Adjuvant BS 1000 was added at 0.2% v/v. The lowest and highest recommended doses of glyphosate for flaxleaf fleabane are 750 and 1500 g a.i. ha−1, respectively.

The glyphosate treatment was applied to the plants using a moving-boom laboratory twin nozzle sprayer sited 40 cm above the seedlings, with a water volume of 110 L ha−1 at a pressure of 250 kPa. A moving belt holds the nozzle at a speed of 1 ms−1. The dose-response experiment was carried out at the Waite Campus of the University of Adelaide, South Australia, after 3–4 months from the seedling transplantation in March 2012.

Plants treated with glyphosate were held in the spray treatment laboratory for 3 h to allow the herbicide to dry before being returned to the glasshouse or outdoors. Plants were watered as required. Four weeks after the application of glyphosate, plants were recorded as dead (susceptible) or alive (resistant). Any plants with green tissue, even if pale, were considered resistant, as they would recover later.

Data analysis

Dose-response data were subjected to probit analysis version 1.63 (US Department of Agriculture, to determine the herbicide dose-response relationships from the percentage of surviving plants. LC50 (the herbicide dose causing 50% plant mortality) was calculated for each population. The difference in resistance levels between populations was determined by comparing the ratio of LC50 for each resistant population compared to the susceptible population.


The fifteen populations of flaxleaf fleabane showed variation in survival rates to glyphosate applications at the highest recommended dose 1500 g a.i. ha−1 in a previous study (Malone et al., 2012) and, hence, were chosen for this study to determine the level of resistance to glyphosate.

Fourteen populations of flaxleaf fleabane resistant to the highest recommended dose of glyphosate (1500 g a.i. ha−1) were confirmed for resistance (Fig. 1). In comparison, the response of the susceptible population (FB1) of flaxleaf fleabane to six rates of glyphosate (0, 187.5, 375, 750, 1500 and 3000 g a.i. ha−1) is shown in Fig. 2. The susceptible population (FB1) was totally killed when treated with the lowest recommended dose of glyphosate (750 g a.i. ha−1) and the higher doses. It was also controlled well (75%) at the rate of 375 g a.i. ha−1, which is below the recommended rates. The survival rate of six resistant populations and one susceptible population of flaxleaf fleabane, following treatment with different rates of glyphosate, is shown in Fig. 3.

Fig. 1
figure 1

Response of the fourteen resistant populations of flaxleaf fleabane 4 weeks after treatment with the highest recommended rate of glyphosate (1500 g a.i. ha−1 glyphosate)

Fig. 2
figure 2

Response of the susceptible population (FB1) of flaxleaf fleabane 4 weeks after treatment with the six rate of glyphosate (0, 375, 750, 1500, 3000 and 6000 g a.i. ha−1)

Fig. 3
figure 3

Response of one susceptible and six resistant populations of flaxleaf fleabane to six rates of glyphosate. Each data point is the mean of three replicates ± standard error (SE)

The responses of the resistant populations to glyphosate varied and were grouped into one of six responses arbitrarily based on LC50 values and representatives of each response are illustrated.

Among the resistant populations, the population that was most sensitive to the highest recommended rate of glyphosate (1500 g a.i. ha−1) was FB5c, followed by NNSW4. Populations Fle01, Fle23, and NNSW14 were the most resistant to the recommended rates of glyphosate.

The LC50 values for glyphosate calculated from the probit analysis for the 15 flaxleaf fleabane populations (Table 2) showed that the population responses fell into seven groups [one susceptible (control) and six resistant].

Table 2 LC50 values of flaxleaf fleabane populations tested for glyphosate resistance. R/S is the ratio of the LC50s of the resistant populations to that of the susceptible population (FB1)

The LC50 values for the FB6c, FB5c and SEQLD3B populations (group 1) were the lowest and varied from 440 to 511 g a.i. ha−1 and were 4.7- to 5.44-fold more resistant than the susceptible population (FB1). The LC50 values for the Fle08, SEQLD5, NNSW4 and NNSW6 populations (group 2) varied from 659 to 737 g a.i. ha−1 and were 7- to 7.9-fold more resistant than the susceptible control. The FB7c, FB3c and FB2c populations (group 3) formed a low moderate group, with LC50 values between 806 and 827 g a.i. ha−1, giving 8.6- to 8.8-fold resistances. The LD50 for the NNSW14 population was 1035 g a.i. ha−1, giving 11-fold resistances to glyphosate. Populations Fle02 and Fle23 (group 5) showed the second highest LC50 values, ranging from 1336 to 1404 g a.i. ha−1, giving 14.2- to 14.9-fold resistance. The Fle01 population was the most resistant with LC50 of 2217 g a.i. ha−1, giving 23.6-fold resistance at the seedling stage.


Walker et al. (Walker et al., 2011) reported low levels of glyphosate resistance (two to sevenfold) in several populations of flaxleaf fleabane from northern NSW and southern Queensland. Many glyphosate-resistant populations have relatively low levels of resistance, such as annual ryegrass (Wakelin et al., 2004), awnless barnyard grass in Australia (Walker et al., 2011) and flaxleaf fleabane in Spain (Dinelli et al., 2008). On the other hand, there is more than 100-fold resistance in flaxleaf fleabane in IN, USA (Davis et al., 2008). These variations in the level of herbicide resistance may be the result of different resistance mechanisms (Preston et al., 2009). The four most resistant populations tested in this study were withstanding at rates of up to 12,000 g a.i. ha−1 glyphosate (eight times the recommended rate; Fig. 3). This result suggests that increasing herbicide dose will not improve weed control when resistance exists in a field. Therefore, alternative strategies will be required to control glyphosate-resistant flaxleaf fleabane populations. Furthermore, the relative significance of these differences among weed populations relates to the success of numerous management strategies in discontinuing or minimizing the dispersal of resistance to neighbouring regions, plantations and agricultural areas (Osuna et al., 2011). For example, in empirical studies on the long-distance spread of Conyza canadensis (Dauer et al., 2007) concluded that wind-dispersed weeds withstand any single practice of farm management as a practical controlling possibility for weed resistance to herbicides. Consequently, dispersal of weed seeds requires proactive management practices to prevent and/or at least minimize the growing invasions of herbicide resistance in undesirable weeds. Therefore, data on the mechanisms of resistance dispersion of C. bonariensis are required for the design of effective resistance management approaches for a cropping system.


The evolution of resistance in C. bonariensis worldwide to the commonly used, highly effective, systemic herbicide glyphosate, which is non-selective and wide spectrum, is of particular concern because this herbicide is important for the sustainability of grain cropping in Australia. The resistant populations tested in dose-response experiment varied in their responses to glyphosate from two to eight times the recommended rate. The different dose responses obtained may indicate different mechanisms of resistance. This can possibly be attributed to an independent evolution of resistance.

Availability of data and materials

Not applicable



The dose that more popular used in this case of foliar application


Northern New South Wales


South Australia


Standard error


South-eastern Queensland


Southern New South Wales


Volume per volume




  • Aves C, Preston C, Gill G, Weston LA. Control of Conyza bonariensis (L.) Cronquist in mixed farming systems. Herbicide resistance in Conyza bonariensis (L) Cronquist (flaxleaf fleabane) populations from northeast Victoria and its management in mixed farming systems. 2017:122.

  • Dauer JT, Mortensen DA, Vangessel MJ (2007) Temporal and spatial dynamics of long-distance Conyza canadensis seed dispersal. Journal of Applied Ecology. 44(1):105–114

    Article  Google Scholar 

  • Davis VM, Gibson KD, Johnson WG (2008) A field survey to determine distribution and frequency of glyphosate-resistant horseweed (Conyza canadensis) in Indiana. Weed Technology. 22(2):331–338

    Article  CAS  Google Scholar 

  • Dinelli G, Marotti I, Bonetti A, Catizone P, Urbano JM, Barnes J (2008) Physiological and molecular bases of glyphosate resistance in Conyza bonariensis biotypes from Spain. Weed Research. 48(3):257–265

    Article  CAS  Google Scholar 

  • Malone J, Cook A, Wu H, Hashem A, Preston C (2012) Management of glyphosate resistant weeds in non-agricultural areas. NSW. 41:31

    Google Scholar 

  • McGillion T, Storrie A (2006) Integrated weed management in Australian cropping systems–a training resource for farm advisors. CRC for Australian Weed Management, Adelaide

    Google Scholar 

  • Moreira MS, Nicolai M, Carvalho SJP, Christoffoleti PJ (2007) Glyphosate-resistance in Conyza canadensis and C. bonariensis. Planta Daninha. 25(1):157–164

    Article  Google Scholar 

  • Osuna MD, Okada M, Ahmad R, Fischer AJ, Jasieniuk M (2011) Genetic diversity and spread of thiobencarb resistant early watergrass (Echinochloa oryzoides) in California. Weed Science. 59(2):195–201

    Article  CAS  Google Scholar 

  • Owen MJ, Owen RK, Powles SB (2009) A survey in the southern grain belt of Western Australia did not find Conyza spp. resistant to glyphosate. Weed Technology. 23(3):492–494

    Article  CAS  Google Scholar 

  • Preston C, Wakelin AM, Dolman FC, Bostamam Y, Boutsalis P (2009) A decade of glyphosate-resistant Lolium around the world: mechanisms, genes, fitness, and agronomic management. Weed Science. 57(4):435–441

    Article  CAS  Google Scholar 

  • Randall RP (2017) A global compendium of weeds: RP Randall

    Google Scholar 

  • TERZİOĞLU S, ANŞİN R (2001) A chorological study on the taxa naturalized in the Eastern Black Sea Region. Turkish journal of Agriculture and Forestry. 25(5):305–309

    Google Scholar 

  • Wakelin AM, Lorraine-Colwill DF, Preston C (2004) Glyphosate resistance in four different populations of Lolium rigidum is associated with reduced translocation of glyphosate to meristematic zones. Weed Research. 44(6):453–459

    Article  CAS  Google Scholar 

  • Wakelin AM, Preston C (2006) Inheritance of glyphosate resistance in several populations of rigid ryegrass (Lolium rigidum) from Australia. Weed Science. 54(2):212–219

    Article  CAS  Google Scholar 

  • Walker S, Bell K, Robinson G, Widderick M (2011) Flaxleaf fleabane (Conyza bonariensis) populations have developed glyphosate resistance in north-east Australian cropping fields. Crop Protection. 30(3):311–317

    Article  CAS  Google Scholar 

  • Walker SR, Robinson GR, editors. Flaxleaf fleabane-the next glyphosate resistant weed? Proceedings of the 16th Australian Weeds Conference, Cairns Convention Centre, North Queensland, Australia, 18-22 May, 2008; 2008: Queensland Weed Society.

  • Wu H (2009) Conyza bonariensis (L.) Cronquist. The Biology of Australian Weeds. 3:85–101

    Google Scholar 

  • Wu HW, Walker SL, Taylor I, Robinson GR, editors. Biology and management of flaxleaf fleabane (Conyza bonariensis (L.) Cronquist). 15th Australian Weeds Conference, Papers and Proceedings, Adelaide, South Australia, 24-28 September 2006: Managing weeds in a changing climate; 2006: Weed Management Society of South Australia.

Download references


Appreciation is extended to the AusAID organization for the financial support during my study, and the University of Adelaide for giving this opportunity to conduct this research as part of my master’s degree.


This research was fully funded by the AusAID organization.

Author information

Authors and Affiliations



All work was done by MH under supervision and advice of CP and JM. MH was a major contributor in writing the manuscript. The authors read and approved the final manuscript.

Corresponding author

Correspondence to Mohammed Hussein Minati.

Ethics declarations

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Minati, M.H., Preston, C. & Malone, J. Resistance of flaxleaf fleabane (Conyza bonariensis (L.) Cronquist) to glyphosate. Bull Natl Res Cent 44, 68 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: