Controlling weeds with fungi, bacteria and viruses: a review

Abstract

Weeds are a nuisance in a variety of land uses. The increasing prevalence of both herbicide resistant weeds and bans on cosmetic pesticide use has created a strong impetus to develop novel strategies for controlling weeds. The application of bacteria, fungi and viruses to achieving this goal has received increasingly great attention over the last three decades. Proposed benefits to this strategy include reduced environmental impact, increased target specificity, reduced development costs compared to conventional herbicides and the identification of novel herbicidal mechanisms. This review focuses on examples from North America. Among fungi, the prominent genera to receive attention as bioherbicide candidates include Colletotrichum, Phoma, and Sclerotinia. Among bacteria, Xanthomonas and Pseudomonas share this distinction. The available reports on the application of viruses to controlling weeds are also reviewed. Focus is given to the phytotoxic mechanisms associated with bioherbicide candidates. Achieving consistent suppression of weeds in field conditions is a common challenge to this control strategy, as the efficacy of a bioherbicide candidate is generally more sensitive to environmental variation than a conventional herbicide. Common themes and lessons emerging from the available literature in regard to this challenge are presented. Additionally, future directions for this crop protection strategy are suggested.

Evolution of the biocontrol active substances in the framework of the European Pesticide Regulation (EC) No. 1107/2009

“…However, bioherbicides (fungi, bacteria and virus) seem to be a worthwhile subject for research because of their reduced environmental impact compared with chemical herbicides, despite several obstacles (selection of candidates, efficiency in the field, commercial profitability). Bioherbicides could be an alternative option for the management of weeds in the future …”

Production of bioherbicide by Phoma sp. in a stirred-tank bioreactor

“…The development of safe and eco-friendly herbicides is an emergent necessity to control weeds in these cultivations (Yang et al 2014). Biological weed control strategies can potentially address this need and provide novel modes of action that will inhibit the growth of weeds that are resistant to more commonly used herbicides (Harding and Raizada 2015). Inundative biological control (which refers to the application of propagation of fungal spores or bacterial suspensions in concentrations that would not normally occur in nature with the intention of destroying a pest species within a managed area) is the strategy more employed (Bailey et al 2011).…”

“…For this reason, the future trend is the production of herbicidal compounds by fermentation, extract it from fermented broth, and use this compound in a more stable formulation. This strategy will not be limited on the continued survival of a given organism in an uncontrolled environment (Harding and Raizada 2015). …”

Draft Genome Sequence of the Plant Growth–Promoting Pseudomonas punonensis Strain D1-6 Isolated from the Desert Plant Erodium hirtum in Jordan

“…Recent discoveries have indicated that herbicides might be generated from microbial sources such as plant endophytes to protect plants from invasive and parasitic plant species (1, 2). Some of these endophytes produce antiherbicide properties that can counteract the function of commercial herbicides.…”