Weed control is one of the most important steps in agricultural production. The sales of herbicides ranks first among the global market share of pesticides. However, the use of a large number of chemical herbicides has caused environmental problems such as water quality degradation and soil pollution, especially the constant occurrence of resistant weeds, which has brought great challenges to agricultural production. According to statistics, as of 2018, a total of 495 cases (biotypes) of resistant weeds have been reported worldwide, involving 255 types of weeds. In China, from the first report of weed resistance in 1992 to 2018, a total of 44 resistance cases have been reported, and the trend of resistant weeds is not optimistic.
With the increase of global environmental awareness and the need for sustainable agricultural development, the development of bio-herbicides with good environmental compatibility, high selectivity and strong biological activity is urgently needed. This trend has become inevitable for the development of contemporary pesticides. Although there are few mature bio-herbicide products on the market, bio-herbicides have become one of the important research and development areas for scientific research institutions and biological pesticide companies. In this article, we hope to help people better understand this market and better grasp the development trend of bio-herbicides by sorting out the current status of the global market, the major bio-herbicide companies and currently available products.
Main categories and characteristics of bio-herbicides
According to a report of MarketsandMarkets, the global market value of bio-herbicides reached $ 800 million in 2016, and will grow at a compound annual growth rate of 14.5%, and is expected to reach $1.5 billion in 2021. This shows the huge market growth potential of bio-herbicides.
According to Wikipedia's definition of bio-herbicide, it refers to a class of natural substances that use biological toxins, pathogenic bacteria, and other microorganisms to control weeds. At present, the common bio-herbicide and the development hotspot are mainly microbial herbicides, which mainly include two types:
1）Living microorganisms: mainly refer to phytopathogenic organisms (fungi, bacteria, and viruses), with the most common one being phytopathogenic fungi;
2) Microbial metabolites: mainly use the toxins and antibiotics produced during the metabolism of these microorganisms, including peptides, terpenes, macrocidins and phenolic resins.
In the field of microbial herbicides, what receive the most studies are fungal bio-herbicides, followed by bacterial herbicides, and viral herbicides are rare.
Among microbial herbicides, fungal herbicides have been most studied. According to research, fungal microorganisms with biological weeding activity mainly involve nine genera such as Colletotrichum, Fusarium, Alternaria, Cercospora, Puccinia, Entyloma, Ascochyta, and Sclerotinia. However, fungal conidial formulations have not brought significant social and economic benefits due to their strict environmental requirements and excessive requirements for technical issues in mass production, formula and storage, etc.
Bacteria with biological weeding potential are mainly rhizobacteria, mainly involve eight genera, i.e., Pseudomonas, Enterobacter, Flavobacterium, Citrobacter, Achromobacter, Alcaligenes, Xanthomonas
. These soil microbial formulations can directly act on the seeds and seedlings of the target weeds, and can be used for researching appropriate release technologies, which are two key points of rhizobacteria application in biological weeding practices.
Development Limits and Prospects of Bio-herbicides
Single host, narrow weeding spectrum
Ultimately, microbial herbicides are actually the pathogens of weeds. And because of this, the targets of biological herbicides are more specific. However, the agricultural ecosystem is complicated, and there are many kinds of weeds. A microbial herbicide that can only control one kind of weed cannot be time-saving and labor-saving. Therefore, biological herbicides have limitations in terms of practical promotion and large-scale use.
Weed control susceptible to environmental conditions and unstable
Like other biological pesticides, the active ingredients of bio-herbicides are mainly living microorganisms that are sensitive to climate conditions such as temperature and humidity. Among them, humidity and dew period are the main limiting factors, which can directly affect the germination, invasion, conidiation and re-infection of fungal spores and propagules, and thus affect the control effect of fungal herbicides. In addition, in general, microbial herbicides cannot be applied in combination with chemical pesticides at the same time, which greatly limits its promotion. If their interaction is beneficial to one or both parties, it will help the large-scale promotion of microbial herbicides.
Difficulty in fermentation and dosage form processing
At present, large-scale production of herbicide cells is mainly carried out by fermentation in the industry. However, some fungi are not easy to reproduce, or have decreased conidiation, poor conidial viability, reduced virulence after multi-generation reproduction, or poor stability after formulating, which affect its mass production and commercialization. The active ingredients of microbial herbicides are living organisms, which are water insoluble particulate matter. The granularity and hydrophobicity will directly affect the physical properties of the formulation such as wetting, dispersing and suspending properties, making it more difficult in formulation processing than chemical herbicides.
In the 21st century, countries around the world are speeding up the development of organic agriculture. According to the "World Organic Agriculture Overview and Trend Forecast 2018" released by FiBL-IFOAM (Research Institute of Organic Agriculture and International Federation of Organic Agriculture Movements), the agricultural land area managed organically was 57.8 million hectares in 2016. According to the data from Ecovia Intelligence, the total sales of organic foods (including drinks) in the past two decades have grown from less than US $ 15 billion to US $ 90 billion in 2016. The organic agriculture marked by ecology, sustainability, high efficiency and high added value inevitably requires safe, efficient and environmentally friendly biological pesticides. It is foreseeable that the rapid development of organic agriculture will drive the rapid development of biological pesticides, including bio-herbicides.