Achievements, Developments and Future Challenges in the Field of Bioherbicides for Weed Control: A Global Review

Abstract

The intrusion of weeds into fertile areas has resulted in significant global economic and environmental impacts on agricultural production systems and native ecosystems, hence without ongoing and repeated management actions, the maintenance or restoration of these systems will become increasingly challenging. The establishment of herbicide resistance in many species and unwanted pollution caused by synthetic herbicides has ushered in the need for alternative, eco-friendly sustainable management strategies, such as the use of bioherbicides. Of the array of bioherbicides currently available, the most successful products appear to be sourced from fungi (mycoherbicides), with at least 16 products being developed for commercial use globally. Over the last few decades, bioherbicides sourced from bacteria and plant extracts (such as allelochemicals and essential oils), together with viruses, have also shown marked success in controlling various weeds. Despite this encouraging trend, ongoing research is still required for these compounds to be economically viable and successful in the long term. It is apparent that more focused research is required for (i) the improvement of the commercialisation processes, including the cost-effectiveness and scale of production of these materials; (ii) the discovery of new production sources, such as bacteria, fungi, plants or viruses and (iii) the understanding of the environmental influence on the efficacy of these compounds, such as atmospheric CO2, humidity, soil water stress, temperature and UV radiation.

Colletotrichum echinochloae: A Potential Bioherbicide Agent for Control of Barnyardgrass (Echinochloa crus-galli (L.) Beauv.)

“…Among these species, only Collego (LockDown), BioMal, Velgo, and Lubao1 have been successfully commercialized. This genus of fungi has been reported to control various weeds around the world and has excellent potential to develop into a commercial mycoherbicide [ 54 ]. Here, in this study, we demonstrated that C. echinochloae had the potential to be developed as a mycoherbicide for the management of barnyardgrass ( Echinochloa crus-galli (L.) Beauv.).…”

Novel and holistic approaches are required to realize allelopathic potential for weed management

“…Even when all of these issues are resolved, it is possible that synthesis of these compounds on sufficiently large scale for field application is prohibitively, or at least antagonistically, expensive (Roberts et al, 2022), owing to their structural complexity and often a lack of preceding work undertaken to optimize their production. Such high production costs of bioherbicides can be an even greater issue if new, cheap, effective ‘traditional’ herbicides are released into the same market; bioherbicidal formulations of the fungus Colletotrichum gloeosporioides f.sp.…”

“…application is prohibitively, or at least antagonistically, expensive (Roberts et al, 2022), owing to their structural complexity and often a lack of preceding work undertaken to optimize their production.…”

Nature-Based Herbicides and Micro-/Nanotechnology Fostering Sustainable Agriculture

“…103 In addition, recent studies have sought to understand the herbicidal action of different molecules produced by plants, bacteria, fungi, and viruses to generate new modes of action in the commercial scenario to solve cases of resistance. 104 This advantage is related to the multisite action of allelochemicals, an alternative to commercial formulations with high plant specificity. 105 Increasing risk awareness of chemical herbicide use and the imminent ban on glyphosate herbicides in the European Union should further encourage and enable the development of natural alternatives.…”

“…For example, registration with the Environmental Protection Agency is expensive and can extend the deadlines for bioherbicides to be available for use by farmers. 104 In addition, many countries make no legislative distinction between natural and conventional formulations, restricting the widespread use of all herbicides, including bioherbicides. 132 Bioherbicides remain new to the market, and formulation changes could be necessary to increase efficiency, even after product registration.…”