History of Weed Science

Historical books and articles about weed science show that weeds have been known to exist for thousands of years, since the start of settled food production. During that time, humans also discovered that the output of their preferred crop, typically coarse-grain cereals, was highest when it was cultivated in the absence of competitive plants that grew in the same habitat. Such species would have been manually eliminated by our forebears to mitigate the yield reductions caused by weed competition. This was an early attempt to suppress weed growth in inhabited areas transitioning to an agricultural-based lifestyle.

Archeological artifacts and ancient writings also certify the decline in yield due to weeds and the use of several tactics for managing them (Radosevich et al. Reference Radosevich, Holt and Ghersa1997). By following the historical trajectory of weed science in Canada and the United States, Timmons (Reference Timmons2005) determined that before 1200 CE or even 1500 CE, only a small number of agricultural leaders and farming communities identified weeds as a major problem and developed an interest in weed management. However, the development of weed science as a separate field of study does not correspond with the presence of weeds in cropped and non-cropped areas. The history of weed research is likely less than 100 years old, paralleling the history of industrialized agriculture (Radosevich et al. Reference Radosevich, Holt and Ghersa1997). Some plant protectionists and weed scientists would argue that the invention of phytotoxic chemicals and herbicides for weed control marked the beginning of the scientific study of weeds. Early in the 20th century, sulfuric acid and inorganic copper salts were the first substances utilized to suppress weeds (Timmons Reference Timmons2005). The production of 2,4-D herbicide by Pokorny (Reference Pokorny1941) and the discovery of its herbicidal properties as a plant growth regulator by Hamner and Tukey in 1944 were the first accounts of a synthetic organic chemical used to manage weeds (Stephenson et al. Reference Stephenson, Solomon, Frank, Hsiung and Thompson2001). These events started planned weed management opportunities and, some would argue, the inception of weed science as a specific discipline.

Weed science as a discipline has succeeded in connecting university researchers, industrial researchers, university extension workers, and farmers to effectively introduce chemical weed control and other weed management practices. This integration can be considered as a model for pushing new technology into mainstream society. Wilfred W. Robbins was the professor who developed the first weed science course and co-wrote the first textbook on weed management, Weed Control, in 1942 (Zimdahl Reference Zimdahl2010). This book served as a source of the widespread introduction of weed science as a specific course and later as a separate discipline in the United States and worldwide (Zimdahl Reference Zimdahl2010). Alden Springer Crafts from the United States was the first person to claim the title of “weed scientist.” Robbins provided the necessary momentum to create the scientific study of weeds, but Crafts provided credibility to weed science through research work and prolific writing (Zimdahl Reference Zimdahl2010). George Knowles was the first person who worked full-time as a weed scientist in Canada (Timmons Reference Timmons2005).

Today, weed science is a well-established discipline, but it is still relatively smaller compared with allied crop protection disciplines such as entomology and plant pathology. In its relatively short history, this dynamic discipline has seen dramatic booms and busts from widespread adoption and prolific success of chemical herbicides to the rapid evolution of large-scale herbicide-resistance evolution across the globe challenging conventional, simplistic weed control programs. We are at the crossroads of ever-increasing herbicide-resistance issues, changing land use and management systems, and impressive technological advancements and digital disruption. On the other hand, significant progress has been made, and there is a further push to explore weed management implications of agroecology and integrated pest management (IPM) principles (Riemens et al. Reference Riemens, Sønderskov, Moonen, Storkey and Kudsk2022). These factors are shaping weed science as a highly interactive, holistic, and technologically advanced field of agricultural sciences.

Weed Science Education Worldwide

Globally, several educational institutes work in numerous disciplines. Higher (university-level) education particularly focuses on specialized, discipline-wise educational training and research. The United States alone has the highest number of universities accounting for 3,982 in the public and private education sectors (Table 1). Russia has 3,000 universities, 47 in the agriculture category. Underdeveloped countries in Asia and Africa still have less focus on agricultural studies. Overall, many universities were specifically established to pursue research and education in the field of agriculture, while many others have agriculture faculties offering different courses and degree programs related to agriculture.

Table 1. Total number of universities, agricultural universities, and universities involved in weed science education worldwide. ^a

^a The list of universities comes only from the countries that have a population of more than 5 million. Countries are ordered alphabetically.

From the weed science point of view, several universities have special weed science departments (Table 1), while other universities provide education on weed science aspects within crop protection, agronomy, and ecology departments. Also, different research institutes offer several services from working on projects under ecology, biology, and management to providing extension services for controlling weeds and decreasing their economic losses. Moreover, a lot of work has been compiled by several authors in the form of specific books that focus on weed ecology, biology, and management options (Table 2). Also, there are specialized journals and specific weed science societies (Table 3) that are working for the betterment of the weed science discipline.

Table 2. List of some important books related to weed science

^a The books are listed in descending order (newest to the oldest).

Table 3. List of important weed science societies, their specific activities (including conferences/events/meetings, specific journals, educational resources), and their official website links.

Globally, approximately 7% of all universities that offer agricultural education have dedicated weed science departments that work on weed biology, ecology, and management (Table 1). Some universities also offer weed science degree programs or at least certain courses in degrees related to associated disciplines, such as plant protection, agronomy, and ecology. Substantial advances, such as separate weed science disciplines and known specialized journals and conferences in weed science, have been made worldwide. Also, there are international, regional, and national weed science societies that work to promote and encourage the development of weed- related knowledge and the impact of weeds on society. For example, the WSSA states that its basic purpose is that it “promotes research, education, and extension outreach activities related to weeds; provides science-based information to the public and policy makers; fosters awareness of weeds and their impacts on managed and natural ecosystems; and promotes cooperation among weed science organizations across the nation and around the world” (WSSA 2023b). Several authors have written comprehensive literature in the form of books (Table 2) and review articles (Buddenhagen et al. Reference Buddenhagen, Bourdȏt, Cripps, Bell, Champion, Dodd, Eerens, Ghanizadeh, Griffiths, Harrington and Heenan2022; Flessner et al. Reference Flessner, Burke, Dille, Everman, VanGessel, Tidemann, Manuchehri, Soltani and Sikkema2021; MacLaren et al. Reference MacLaren, Storkey, Menegat, Metcalfe and Dehnen-Schmutz2020; Westwood et al. Reference Westwood, Charudattan, Duke, Fennimore, Marrone, Slaughter, Swanton and Zollinger2018) that specifically cover the discipline of weed science.

Scope of Weed Science

Weed science is a broad field that addresses significant biotic stresses that can cause huge economic losses to the agricultural sector and economy of any country, leading to exacerbating the problem of food insecurity. In a comprehensive analysis, Oerke (Reference Oerke2006) reported that weeds potentially cause up to 34% loss to crop yields globally. These losses are much greater than those caused by insect pests and diseases that reduce crop yields by 18% and 16%, respectively (Oerke Reference Oerke2006). Due to their persistent nature, weeds are typically given less attention than they deserve. Farmers pay more attention to unexpected, unanticipated epidemics of insect pests or diseases, because they are less accustomed to their presence (Moss Reference Moss2019). Weeds, on the other hand, are often considered to be a “business as usual” kind of problem, overlooking the magnitude of damages they pose to crop productivity and quality. A parallel condition exists in the public healthcare sector: policy makers devote the most resources to handling acute diseases compared with chronic diseases, which usually receive little attention (Fernandez-Quintanilla et al. Reference Fernandez-Quintanilla, Quadranti, Kudsk and Barberi2008).

One of the greatest strengths of weed science is that it offers an arguable and problem-solving approach (Fernandez-Quintanilla et al. Reference Fernandez-Quintanilla, Quadranti, Kudsk and Barberi2008). In this context, this discipline can be considered a model that combines several disciplines and utilizes a systematic approach to resolve practical issues. In addition, the weed science discipline is an exceptional example of how to cover the gap between scientific knowledge and its practical management, offering nonfragmented scientific knowledge and practical advice and opportunities to the end-users.

Weed science has had great success in effectively, affordably, and safely managing the weeds in a wide range of crops. Although a huge portion of this achievement has been due to the availability of low-cost, effective synthetic herbicides, sole reliance on chemical control has led to the widespread herbicide-resistance evolution in addition to increasing environmental health concerns (Gaines et al. Reference Gaines, Duke, Morran, Rigon, Tranel, Küpper and Dayan2020). A variety of cultural, biological, physical, and IPM-oriented weed management techniques have also been developed and introduced at a commercial scale, as a result of coevolution with the societal request for more environment-friendly crop management systems. IPM is an interdisciplinary approach that involves pest management principles based on relevant knowledge and practices in agronomy, entomology, plant pathology, nematology, weed science, ecology, horticulture, economics, and systems science (Thill et al. Reference Thill, Lish, Callihan and Bechinski1991). Despite the heavy reliance on chemicals for weed management in broadacre crop production over the past few decades, weed research has been focusing on alternative approaches and their integration for effective IWM (Jabran and Chauhan Reference Jabran and Chauhan2018). In fact, Oerke (Reference Oerke2006) indicated that the higher efficacy of weed management compared with insect pests or disease management was because of the usage of several methods for controlling weeds.

Weeds are the masters of adaptation, hence it is critical to continuously track their evolution in order to better manage them. The focus on studying biology and ecology continues to grow, as it helps better understand shifting weed dynamics and behavior in response to climatic and management factors, ultimately helping in the development of new, improved weed management options (Westwood et al. Reference Westwood, Charudattan, Duke, Fennimore, Marrone, Slaughter, Swanton and Zollinger2018). Therefore, understanding weed biology and ecology is integral to sustainable weed management, as weed populations adapt and evolve in response to new selective pressures. Another important point to be made about weed management is that all these achievements have been accomplished with relatively few financial resources (Matloob et al. Reference Matloob, Safdar, Abbas, Aslam, Khaliq, Tanveer, Rehman and Chadhar2020).

Moving forward, weed science has immense scope as a discipline. In the wake of changing climate and mounting food security and food safety concerns around the globe, effectively managing weeds is as important or arguably more important than most other biotic and abiotic production constraints. With many modern digital technologies coming online, weed science could be at the forefront of smart mechanized farming. This presents numerous opportunities for the next generation of weed scientists, farmers, and practitioners, as well as entrepreneurs.

Costs of Weeds

Costs of weeds consist of weed management expenses as well as productivity losses due to weeds (Saunders et al. Reference Saunders, Greer, Bourdôt, Saunders, James, Rolando, Monge and Watt2017). Both these factors have a significant impact on the sustainability of productive land usage. Knowledge of the costs of weeds is important for (1) prioritization of key target weed species for research and management; (2) development of cost-effective weed control strategies in the light of benefit-cost analyses; and (3) logical allocation of funding for research, development, and extension (RD&E) in the weed science sector.

Economic yield losses in several crops due to specific weeds in a specific region or country are shown in Table 4. The estimate of the total cost of weeds to New Zealand’s agricultural economy was US$1.658 billion (Saunders et al. Reference Saunders, Greer, Bourdôt, Saunders, James, Rolando, Monge and Watt2017). In Australia, the financial cost of the 15 most important weeds in 7 agronomic crops was estimated to be AU$1.182 billion per year (Llewellyn et al. Reference Llewellyn, Ronning, Ouzman, Walker, Mayfield and Clarke2016). The key parts of this cost were management costs for herbicides, which accounted for AU$571 million, the competitive effects of residual weeds were AU$380 million, and tillage for weed control cost AU$206 million, while weed contamination of grain was a minor cost (AU$25 million) (Jones et al. Reference Jones, Vere, Alemseged and Medd2005).

Table 4. Economic yield losses in selected crops/production systems caused by weed interference.

It is important to note that economic and social costs of weeds are often less studied and underestimated due to (1) no concerted effort in the quantification of such losses on large scales, (2) lack of reliable, consistent data, (3) prioritization of funding and resources for developing management tools instead of understanding the actual cost of weed infestations, and (4) limitations surrounding consistent, coherent methodologies and reporting.

Challenges in Weed Science

Weed science was shaped as a specific discipline in the 1950s and has been facing multifarious issues and challenges ever since (Chandrasena Reference Chandrasena2020). Although it is difficult to generalize challenges and problems facing this discipline across different geographic regions, the themes discussed in this section are frequently encountered and are broadly considered to be the major challenges in the field of weed science.

Prospects for Weed Science

Although several leading universities offer education and training in weed science directly or through courses embedded in their crop science–related degrees, the overall number of educational providers within this important discipline is very small on a global scale, especially in underdeveloped countries. The study of basic and fundamental principles of weed science should be compulsory for agriculture students. Weed science students should seek knowledge of weed biology, ecology, and IWM, along with advanced technologies such as remote sensing, artificial intelligence, computing, and robotics. This will diversify students’ skills within weed science while potentially broadening job opportunities for them in agricultural engineering and industry.

Climate change is one of the world’s major challenges (and an opportunity as well), and it will become even more critical for agriculture and weed science in the near future given the increasing global population and food demand. Unfortunately, crop protection as well as weed invasions and weed management will become more difficult under future climatic conditions (Bajwa et al. Reference Bajwa, Farooq, Al-Sadi, Nawaz, Jabran and Siddique2020, Reference Bajwa, Matzrafi and Jugulam2021; Jabran et al. Reference Jabran, Florentine and Chauhan2020). Weed scientists have a key role to play in both mitigation of and adaptation to adverse effects of climate change through more adaptive research using complex climate change scenarios. This might be implemented by reducing tillage practices and avoiding flaming and encouraging conservation tillage practices, site-specific weed management, reduced herbicide rates, and biological and cultural control (Somasundaram et al. Reference Somasundaram, Sinha, Dalal, Lal, Mohanty, Naorem, Hati, Chaudhary, Biswas, Patra and Chaudhari2020). In addressing climate change, the disciplines of weed science and invasion ecology can learn a lot from each other, and there are certain principles and practices that can be exchanged and mutually applied to achieve sustainable outcomes (Sun et al. Reference Sun, Kaleibar, Oveisi and Müller-Schärer2021).

To be effective, weed management strategies must take into account weed ecology in connection to environmental, genetic, and biochemical factors, as well as and molecular biology information. The use of genetic techniques can help to identify and characterize genes that are involved in weed growth and development. This research can lead to the development of new herbicides that target specific genes in weeds, making them more susceptible to management options while reducing their negative impacts. Also, by using techniques such as gene editing and RNA interference, researchers can modify the genetic makeup of weeds to make them more susceptible to herbicides or even to cause them to self-destruct. The economics of both weed-induced production losses and weed control techniques must be taken into consideration when creating an adequate weed science curriculum.

Weed science is an integrative scientific discipline that combines both applied and basic sciences to understand and effectively manage some of the most undesirable plants in agroecosystems. The work of weed scientists is challenging, and several advances have been achieved, including achieving scale as a specific discipline. Still, numerous issues have yet to be fully explored, including the role of molecular biologists, invasion ecologists, and plant physiologists in basic and applied research for vegetation management in agricultural and nonagricultural ecosystems.

In the future, weed science as a discipline needs to be described in more precise and positive ways to attract potential students. Additionally, multidisciplinary weed science needs to be developed or introduced so that students can learn more about the complexity of weeds in farming systems and then go on to find innovative solutions. Topics such as molecular analysis of suspected herbicide-resistant weeds, weed management by genetic tools like RNAi, and weed identification by DNA bar-coding and sequencing need to be incorporated into coursework for weed science students. Also, there is a need for cooperation between government organizations and private industry for the creation of internship/placement programs for weed science graduate students.