Chemical and biological treatments: Pros and Cons

What are Chemical treatments?

The largest group of plant infection, diseases, and crop loss are caused by pathogens such as fungi, viruses, etc and by weeds, pests’ attack. Chemical treatments: a method of agriculture disease management using different chemicals. Chemical treatments act on these diseases causing pathogens and are widely applied in agriculture to control the disease and improve the growth and yield of crops (Pujol et al., 2006). Chemical treatments are formulations of chemicals such as streptomycin sulfate, oxy- tetracycline, atrazine, chlordane, endosulfan, DDT, aldrin, 2,4-Dichlorophenoxyacetic Acid (2,4-D), copper, sulfur, etc., which are toxic, pose risks to people and perform bactericides, insecticides, and fungicides action on pests and pathogens.

Global Market of Chemical treatments

Chemical treatment is the most effective method of control till date (Zhao et al., 2017), having a global market of USD $104.9 billion in 2018 with a growth rate of +3.7% per year to reach $121.3 billion by 2022 (Business Research, 2019).

Advantages (Pros) of Chemical treatments

Advantages of chemical treatments across plant disease management are many, use and application is very easy and robust, covering large fields in less time, selective products depending upon the stages of growth. Production of these chemical agents can be carried out at large scale in minimum time, custom-made depending upon the plant growth and soil filed parameters, commercially available, and the regulatory registration process with agencies is straightforward.

Disadvantages (Cons) of Chemical treatments

These reasons encourage the application of chemical treatment worldwide; however, continuous, and long-term application of chemical agents leads to accumulations in soil and elevates the chemical resistance of plant pathogens (Zhao et al., 2017). In addition, the residues of chemical treatment have greater influence on the ecological system, soil fertility reduction, underground water contamination, affecting animals, and birds, promoting to seriously environment pollution (Gao et al., 2012). To add-on, chemical fungicides and insecticides are expensive, hazardous, progressively discouraged, deliver damaging and negative impact on beneficial soil microorganisms present that support to increase plant growth (Hashem et al., 2019).

Search for Alternate Treatments

On the other hand, increasing demand to reduce the use of chemicals, low-input, low-cost, sustainable products, minimize environmental degradation, restoration of habitat, to preserve the ecosystem has resulted in greater interest and has become a focal point of research (Pozo et al., 2013). Alternative methods like biological control using microorganisms are getting encouraged, popular and progressively applied.

What are Biological treatments?

Biological treatments: a method of agriculture disease management using microbes. The biological interventions with the manipulation and use of native, beneficial soil microorganisms is recognized as a sustainable, non-hazardous, and eco-friendly strategy in agriculture application (Pujol et al., 2006). Application of microorganisms (fungi and bacteria) is also considered as organic farming carried out to increase productivity and disease resistance in crops in modern agriculture. Use of beneficial microbes, such as species of Arbuscular Mycoorhizal Fungi (AMF), Trichoderma, Bacillus subtilis, Pseudomonas fluorescens etc. promote positive impact on the host plant to increase biomass, growth upgrade, higher crop yield, improve nutrient efficiency, increase soil fertility, overcome biotic and abiotic stress conditions, minimize heavy-metal toxicity, promote disease resistance genes, and stimulate to synthesis wide range of antibodies and antimicrobial metabolite. These benefits could augment and terminate the use of chemical pesticides in future (Hashem et al., 2019).

Global Market of Biological treatments

Significant success of using biological control in plant health and disease management was carried out in 20^th century and with advancement in modern biotechnology is predicted to be even more significant in the 21^st century (Gao et al., 2012). Currently, the global markets of biopesticides exceeded USD $3 billion in 2018, several companies worldwide are producing different products, predicted to grow at the rate of 15% per year and is growing at large scale especially in North America and Europe (Global market Insights, 2019).

Advantages (Pros) of Biological treatments

The application of biological control on different variety of seeds, plants and crop delivered increased root and shoot biomass, promoted defense systems against various diseases, increased the soil fertility, developed resistance to stress and drought conditions, and delivered significant higher yields. Under controlled-environment conditions, the mode of action and efficacy of microbial control overrides the chemical fungicides, with reduction in disease (Root rot, Clubroot, Sclerotinia stem rot, Blackleg, Verticillium wilt etc.) severity of more than 80% relative to pathogen inoculated controls (Debao et al., 1993) (Cheah et al., 2000) (Hanson et al., 2000) (Strelkov et al., 2011). Cultivation of crops in contaminated fields or heavy metals concentrated soil was only possible with use of biological control. Use of biological control have a clear edge over chemical treatment in agricultural management.

Disadvantages (Cons) of Biological treatments

However, several challenges are hindering the advancement and popularity of biological control from a scientific model to a viable commercial product. Few of the technical challenges such as major obstacle for massive inoculum productions, culturing obligate symbionts require host plants (Pozo et al., 2013), time consuming, inability to produce resting spores, quality consistence, formulation complications for commercial use (Weller et al., 2007). The antibiotic-producing biocontrol agent used in the treatment of plants, get transferred and when consumed by human and animal develop pathogen resistance against these antibiotics (Panpatte et al., 2016). The potential benefits of biological control are affected by crop management factors such as crop rotation, tillage practices and seeding equipment etc. In addition, nontechnical challenges such as registration process with regulatory agencies, approval of federal USEPA and authorization of agencies within each state is necessary requirement (Stockwell et al., 2007) (Panpatte et al., 2016).

Comparison across Chemical and Biological treatment

Till now, agriculture disease management rely mainly on the application of chemical treatment due to efficient strategy, cost-effective, availability, easy application, however chemical treatment poses serious risks to human health and environment. Therefore, biological treatment overcomes these issues for non-toxic, human and environment friendly, low-cost, however biological formulation production and effect is time consuming, and many companies’ products are under stage of approval for worldwide applications. Table 1, compares the key features across chemical and biological treatment and Figure 1, represents the comparison of chemical and biological treatment on an infected plant.

Table 1: Key features comparison across chemical and biological treatment (Biological and Chemical, 2018).

Key features	Chemical treatment	Biological treatment
Raw material	Non-renewable, costly chemicals	Renewable, low-cost biomass
Catalyst	Metals and oxides	Microbes and enzymes
Operating condition	750 °F and 200-600 atm pressure	Ambient temp and pressure
Energy input	650-1000 kJ/mol NH4	200-350 kJ/mol NH4
Production rate	Quick	Time consuming
Efficiency	50-70%	80-90%
Effect	Rapid	Slow
Cost	Marginal cost	Low cost
Products	Many	Few
Soil health	Deteriorates and degrades	Improves and benefits

Balanced approach

A balanced approach of using biological and chemical treatment needs to be carried out to have a significant result in the plant health and disease management for improved and higher agriculture yield. This approach will deliver multidimensional advantages/benefits of both biological and chemical treatment and comes together with a better formulation choice to be exploited in the field of agriculture with economical and environmental benefits.

References:

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About Author: VINAYAK PACHAPUR, PhD