Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1 -- 1243 2023-02-24 10:04:20 |
2 layout & references Meta information modification 1243 2023-02-27 05:56:37 |

Video Upload Options

Do you have a full video?


Are you sure to Delete?
If you have any further questions, please contact Encyclopedia Editorial Office.
Montull, J.M.; Torra, J. Herbicide-Resistant Cases in Perennial Crops. Encyclopedia. Available online: (accessed on 15 April 2024).
Montull JM, Torra J. Herbicide-Resistant Cases in Perennial Crops. Encyclopedia. Available at: Accessed April 15, 2024.
Montull, José María, Joel Torra. "Herbicide-Resistant Cases in Perennial Crops" Encyclopedia, (accessed April 15, 2024).
Montull, J.M., & Torra, J. (2023, February 24). Herbicide-Resistant Cases in Perennial Crops. In Encyclopedia.
Montull, José María and Joel Torra. "Herbicide-Resistant Cases in Perennial Crops." Encyclopedia. Web. 24 February, 2023.
Herbicide-Resistant Cases in Perennial Crops

Herbicide-resistant weeds challenge sustainable food production in almost all cropping systems in Europe. Herbicide resistance is increasing, and some European countries are among the most affected globally, such as Spain and France. This situation is worsening not only due to herbicide use restrictions but also due to climate change, rendering Mediterranean countries such as Spain particularly susceptible.

Bassia scoparia Bromus Conyza Lolium Salsola kali

1. Introduction

Herbicide-resistant weeds are expected to continue to grow and ultimately threaten crop production on a global basis [1]. Unfortunately, Spain (with around 500,000 km2) with 23 Mha of arable land, in the Mediterranean southwestern corner of Europe, is not an exception. Spain ranks sixth in the world, and second in Europe (after France) in terms of unique herbicide-resistant weed cases [2]. According to the updated information provided in a recent review, it now ranks first in Europe, and fifth in the world, which is right behind the largest countries in the world in terms of both food production and surface area: Canada, USA, Brazil, and Australia [3].
Resistance managements should start with the implementation of integrated weed management (IWM) strategies to reduce the selection pressure and reliance on herbicides [4]. The best IWM measure against herbicide resistance is diversification at all levels: diverse cropping systems or crop rotations, a variety of control methods (non-chemical and chemical), and increasing crop density and delayed seeding [5]. It is acknowledged that all weed control methods, even hand weeding, can promote the evolution of resistance traits in field weed populations, which is why diversity at all levels is crucial.

2. Herbicide-Resistant Cases in Perennial Crops

Glyphosate (Group 9, HRAC legacy group G) is currently the only non-selective post-emergence herbicide registered in Europe [3]. In perennial woody crops, it is still the main (chemical) weed control tool used to manage weeds both under crop plants and along inter-rows [6]. Therefore, it is expected that the high selection pressure with this herbicide will continue or probably will even increase in different cropping systems across the continent. Spain represents a good example of the worsening scenario for perennial crops in Europe. Until the beginning of the 21st century, no cases of glyphosate were reported in this country. However, since then, with the first report for Conyza bonariensis, there has been a fast and steady increase in the number of cases at up to 18, particularly in perennial crops [3]. Unfortunately, the main response to glyphosate resistance has been to switch to another SoA to control glyphosate-resistant populations. Therefore, one of the expected outcomes of this improper management is the evolution of multiple herbicide-resistant weeds in different European perennial crops. In fact, multiple herbicide-resistant populations have already been confirmed in perennial crops from Spain for Lolium and Conyza species [7][8], which will be treated in depth here.

2.1. Genus Conyza

The genus Conyza includes around 100 species distributed all over the world and they are not only observed mainly in tropical climates but also in temperate areas of the Northern Hemisphere [9]. The main weeds species present in Europe are C. bonariensis, C. canadensis, and C. sumatrensis, which are commonly known as fleabanes. The three species are natives of the American continent, and C. bonariensis and C. sumatrensis are from South America, while C. canadensis is from from North America [10].
These species of the Conyza genus are well known for their prominence as weeds, particularly under the rows of perennial crops, where they limit the presence of other weed species and grow with limited competition [10]. Besides these biological attributes, they have natural reduced susceptibility relative to glyphosate at later growth stages together with being prone to evolve resistance relative to this non-selective herbicide [11].
Until very recently, the use of oxyfluorfen (Group 14, HRAC legacy group E) to residually control broadleaf weeds and also some grasses was common in perennial crops [7]. In general, herbicides inhibiting protoporphyrinogen oxidase (PPO), such as oxyfluorfen, are at low risks of resistance evolution in weeds [12][13]. However, due to environmental concerns, the registered dose in Europe for oxyfluorfen has been reduced, so its effectiveness and use is now limited to post-emergence applications [14]. This scenario seriously increased the dependency on other herbicide SoAs, mainly ALS-inhibiting herbicides (Group 2, HRAC legacy group B) such as flazasulfuron, iodosulfuron, and penoxsulam in perennial crops such as citrus, olive, and vineyards. Additionally, these Conyza species have the capacity to evolve resistance relative to ALS inhibitors, with several confirmed cases across the globe [2]. For example, glyphosate-resistant populations were managed with post-emergence ALS inhibitors, i.e., prompting the evolution of multiple herbicide-resistant C. canadensis to both SoAs in Spanish olive orchards [15]. In the worst cases, farmers switch from one SoA to another to manage resistant populations. A C. bonariensis-resistant biotype to at least five SoAs is already present in Spanish olive fields [8].
In susceptible populations to glyphosate, it would be crucial to avoid seed production from any plant surviving the application of ALS-inhibiting herbicides. In this case, a possibility is the mixture of the ALS-inhibiting herbicide with 2,4-D or other auxinic herbicides in order to improve effectiveness. However, in populations that are already resistant, it is very difficult to adequately decide upon the timing of post-emergence contact herbicides, hindering their management only by chemical means. Therefore, the only way to alleviate the evolution herbicide resistant in Conyza species is to implement non-chemical and cultural methods to manage them in perennial crops. These should include a mixture of different modes of action (MoA), mechanical control (mowing and shredding), or cover crops among others. Finally, organic mulches under crop plants or bioherbicides are promising new tools to consider for managing Conyza [16][17].

2.2. Genus Lolium

The species that belong to the genus Lolium and particularly L. rigidum are among the worst herbicide-resistant weeds globally. Multiple herbicide-resistant populations are common in different cropping systems [2]. Currently, L. rigidum is the most worrying and important herbicide-resistant weed species in Mediterranean Europe [3]. Oxyfluorfen, alone or mixed with glufosinate (Group 10, HRAC legacy group H) and glyphosate, were not only applied to control grass and broadleaf weeds in perennial crops but also to prevent and/or control glyphosate-resistant Lolium spp. populations [7][18] with the risk of multiple herbicide resistance evolution. However, in the EU, glufosinate was banned in 2014 and the actual authorized dose rate of oxyfluorfen does not adequately control L. rigidum.
In perennial crops, the main factor that hinders the chemical management of Lolium spp. is the evolution of biotypes with multiple resistance to ALS inhibitors and glyphosate. On a chemical basis, the only way to control these biotypes at the seedling stage is the use of ACCase-inhibiting herbicides (Group 1, HRAC legacy group A), such as propaquizafop, which implies that the selection pressure on this SoA will be very high. In fact, resistance to ACCase inhibitors is the most common case in European winter cereals for L. rigidum [2], stressing the facility to evolve resistance to this SoA in these species [19]. The evolution of multiple herbicide resistance with respect to glyphosate, ACCase inhibitors, and other SoAs (oxyfluorfen and ALS inhibitors) is expected in Mediterranean countries such as Spain. For these reasons, resistant cases can start to appear in Lolium spp. after only three to four seasons, and these biotypes are almost impossible to manage by chemical means [20]. In the worst cases of multiple resistance, the tolerance to seed production should be zero for areas where herbicides are failing. It is important to highlight that the seed bank persistence in the soil for Lolium species is relatively low compared to other weeds at usually 2–3 years; thus, with adequate weed management, including mowing and non-chemical methods, the resistant population should not spread.


  1. Peterson, M.A.; Collavo, A.; Ovejero, R.; Shivrain, V.; Walsh, M.J. The challenge of herbicide resistance around the world: A current summary. Pest Manag. Sci. 2018, 74, 2246–2259.
  2. Heap, I. The International Herbicide-Resistant Weed Database. Available online: (accessed on 30 August 2022).
  3. Torra, J.; Montull, J.M.; Calha, I.M.; Osuna, M.D.; Portugal, J.; de Prado, R. Current Status of Herbicide Resistance in the Iberian Peninsula: Future Trends and Challenges. Agronomy 2022, 12, 929.
  4. Norsworthy, J.; Ward, S.; Shaw, D.; Llewellyn, R.; Nichols, R.; Webster, T.; Bradley, K.W.; Frisvold, G.; Powles, S.B.; Burgos, N.R.; et al. Reducing the Risks of Herbicide Resistance: Best Management Practices and Recommendations. Weed Sci. 2012, 60, 31–62.
  5. Liebman, M.; Staver, C.P. Crop diversification for weed management. In Ecological Management of Agricultural Weeds; Liebman, M., Mohler, C.L., Staver, C.P., Eds.; Cambridge University Press: Cambridge, UK; London, UK, 2001; pp. 322–374.
  6. Duke, S.O. Glyphosate: The world’s most successful herbicide under intense scientific scrutiny. Pest Manag. Sci. 2018, 74, 1025–1026.
  7. Fernández, P.; Alcántara, R.; Osuna, M.D.; Vila-Aiub, M.M.; De Prado, R. Forward selection for multiple resistance across the non-selective glyphosate, glufosinate and oxyfluorfen herbicides in Lolium weed species. Pest Manag. Sci. 2016, 73, 936–944.
  8. Palma-Bautista, C.; Vázquez-Garciá, J.G.; Domínguez-Valenzuela, J.A.; Ferreira Mendes, K.; Alcántara De La Cruz, R.; Torra, J.; De Prado, R. Non-target-site resistance mechanisms endow multiple herbicide resistance to five mechanisms of action in Conyza bonariensis. J. Agric. Food Chem. 2021, 69, 14792–14801.
  9. Noyes, R.D. Biogeographical and evolutionary insights on Erigeron and allies (Asteraceae) from ITS sequence data. Plant Syst. Evol. 2000, 220, 93–114.
  10. Florentine, S.; Humphries, T.; Chauhan, B.S. Chapter 7—Erigeron bonariensis, Erigeron canadensis, and Erigeron sumatrensis. In Biology and Management of Problematic Crop Weed Species, 1st ed.; Chauhan, B.S., Ed.; Academic Press: London, UK, 2021; pp. 131–149.
  11. Amaro-Blanco, I.; Fernández-Moreno, P.T.; Osuna-Ruiz, M.D.; Bastida, F.; De Prado, R. Mechanisms of glyphosate resistance and response to alternative herbicide-based management in populations of the three Conyza species introduced in southern Spain. Pest Manag. Sci. 2018, 74, 1925–1937.
  12. Powles, S.B.; Yu, Q. Evolution in action: Plants resistant to herbicides. Annu. Rev. Plant Biol. 2010, 61, 317–347.
  13. Riggins, C.W.; Tranel, P.J. Will the Amaranthus tuberculatus Resistance Mechanism to PPO-Inhibiting Herbicides Evolve in Other Amaranthus Species? Int. J. Agron. 2012, 2012, 305764.
  14. European Commission (EC). Commission Implementing Regulation (EU) 2017/359 of 28 February 2017 amending Implementing Regulation (EU) No 540/2011 as Regards the Conditions of Approval of the Active Substance Oxyfluorfen. 2017. Available online: (accessed on 21 October 2022).
  15. Mora, D.A.; Cheimona, N.; Palma-Bautista, C.; Rojano-Delgado, A.M.; Osuna-Ruiz, M.D.; de la Cruz, R.A.; De Prado, R. Physiological, biochemical and molecular bases of resistance to tribenuron-methyl and glyphosate in Conyza canadensis from olive groves in southern Spain. Plant Physiol. Biochem. 2019, 144, 14–21.
  16. Cabrera-Pérez, C.; Valencia-Gredilla, F.; Royo-Esnal, A.; Recasens, J. Organic Mulches as an Alternative to Conventional Under-Vine Weed Management in Mediterranean Irrigated Vineyards. Plants 2022, 11, 2785.
  17. Cabrera-Pérez, C.; Royo-Esnal, A.; Recasens, J. Herbicidal Effect of Different Alternative Compounds to Control Conyzabonariensis in Vineyards. Agronomy 2022, 12, 960.
  18. Fernández-Moreno, P.T.; Travlos, I.; Brants, I.; De Prado, R. Different levels of glyphosate-resistant Lolium rigidum L. among major crops in southern Spain and France. Sci. Rep. 2017, 7, 13116.
  19. Vázquez-García, J.G.; Alcántara-de la Cruz, R.; Palma-Bautista, C.; Rojano-Delgado, A.M.; Cruz-Hipólito, H.E.; Torra, J.; Barro, F.; De Prado, R. Accumulation of Target Gene Mutations Confers Multiple Resistance to ALS, ACCase, and EPSPS Inhibitors in Lolium Species in Chile. Front. Plant Sci. 2020, 11, 553948.
  20. Busi, R.; Gaines, T.A.; Walsh, M.J.; Powles, S.B. Understanding the potential for resistance evolution to the new herbicide pyroxasulfone: Field selection at high doses versus recurrent selection at low doses. Weed Res. 2012, 52, 489–499.
Subjects: Agronomy
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to : ,
View Times: 235
Revisions: 2 times (View History)
Update Date: 27 Feb 2023