Title: Bioherbicides for eco-friendly weed management: From fields to commercialization, constraints and solutions for sustainable agriculture
Abstract:
Weeds outcompete crops for natural resources, reducing productivity (growth, yields) and quality of products. Globally, the annual worth of agrochemicals used to protect crops from weeds is estimated to US$75.3 billion. Blind use of chemicals to maximize production ensuring food security for an increasing population exerts many negative environmental impacts and development of resistance among the weed biotypes and creating "superweeds" against herbicides, even presenting a higher risk to soil microbiota and the environment, including human health. Biological management of weeds through bioherbicides, an alternative to chemical herbicides, is an emerging eco-friendly strategy with decent potential for sustainable crop production with minimal environmental impact. Bioherbicides are the liquid or powder formulations based upon weedspecific live microorganisms (fungi, bacteria, viruses) or natural plant products (neem, citrus, clove) applied to overwhelm weed populations in a similar fashion as chemical herbicides. Based upon the biocontrol agent used in the formulation, bioherbicides are classified as: microbial herbicides (microbes) and botanical herbicides (plant extracts/ oils). Opportunities within the bioherbicides industry are abundant propelled by rising organic/ natural farming, regulatory support, increasing resistance to synthetic chemicals, and environmental concerns. The global bioherbicides market valued at US$ 3.93 billion in 2025 and is projected to increase from US$ 4.53 billion in 2026 to US$ 14.06 billion by 2034, expanding at a CAGR of 15.22 % from 2025 to 2034. (Precedence Research, December 4, 2025). Researches on controlling weeds using biocontrol agents, especially foliar fungal pathogens, which had been initiated in 1970s took 10 years in developing and commercializing the first mycoherbicide DeVine in 1981 in the US market followed by the 2nd Collego in 1982. Since than over 26 microbial herbicides based upon fungi, bacteria and viruses have been developed globally, mainly based upon fungal taxa, hence the terms bioherbicides and mycoherbicides, are used interchangeably. Gibbatrianth, a formulation based upon the Indian isolate of Gibbago trianthemae, is the only mycoherbicide known from the developing countries. All the developed bioherbicides are not currently available in the market since they have not performed successfully under field conditions against specific weeds due to complexity of weed diversity across the world, short shelflife, unable to grow and cause infection, and create epiphytotic on the targeted weeds due to environmental conditions of the area of application. For foliar pathogens, biological and environmental factors: temperature, free moisture (lengthy dew requirements) and protection from UV irradiation, all three, are critical for host's infection, short shelf-life and inconsistent efficacy. To overcome the major constraints: virulence, stability, producing sufficient concentration of spores to be economically viable, host range, and dew requirement of the pathogen, the use of fungal biotechnology by genetic manipulation of potential mycoherbicidal agent by protoplast fusion, improvement of fermentors, spraying techniques, modification of the carriers in the inoculum, mass production of stable inoculum, enhancement of mycoherbicidal activity by the application of exogenous cellulases and/or pectinases, and developing consortia of host specific fungal pathogens for simultaneous broad-spectrum weed control. Bioherbicides haven't progressed much in the past 50 years, but hopefully future will be more fruitful "with the right technology applied to overcome the major barriers/constraints, to come up with bioproducts - that are fast acting, economical, safe and efficacious for variety of weed species". For fulfilment this task, a collaborative effort of plant pathologists, microbiologists, weed scientists, biotechnologists, and industrial houses, is needed for sustainable agriculture and getting foods free from carcinogenic herbicides.
