Bio-Pesticides - The Future of Pest Control?
Reasons for developing bio-pesticides
Due to public concern about the risks associated with chemical pesticides, the federal government is re-evaluating registrations granted prior to 1995, with current expectations for public health and environmental protection in mind. The result has been that several older products that have not met the current standards for registration are no longer supported for registration by their manufacturers, and are no longer available for use in agricultural applications. Some bio-pesticides currently being developed in Canada may be excellent alternatives to chemical pesticides.
To compensate for these losses, farmers are looking at integrated approaches to pest control, including the use of biologically prepared pesticides which are deemed by the Pest Management Regulatory Agency (PMRA) - the federal regulator of pesticides in Canada - to have lower environmental risks, as well as human and animal health risks.
Another factor stimulating the search for biologically prepared pesticides is the issue associated with invasive weeds. Many such weeds are associated with waterways, and therefore require products that have a lower ecological impact.
Also, many urban municipalities in Canada are banning the use of chemical pesticides, which opens an opportunity to develop biological alternatives for the control of weeds, diseases, and insect pests in urban environments. Furthermore, over 180 weed species that developed resistance to chemical herbicides have been reported worldwide, with 27 species in Canada and 12 species on the Canadian prairies. While many multi-national companies have diverted much of their research and development efforts toward genetics and away from the discovery of new chemistries, bio-pesticides represent potentially new modes of action to combat herbicide-resistant weeds.
What characteristics should bio-pesticides possess?
In order to be acceptable to users, bio-pesticides must be effective in controlling the pest(s) that they are designed to control. Many bio-pesticides are single host specific, but it is desirable to have a bio-pesticide that can control a wider range of targets.
Biological pesticides need to provide predictable performance standards, and they need to do so inexpensively. Agriculture and Agri-Food Canada scientists in Saskatoon developed formulations that may be applied pre-emergence or post emergence to control common weeds.
The Strategic Framework
There has been significant development of biologically developed pesticides for the control of certain broadleaf weeds. For example, scentless chamomile and Canada thistle in crops, as well as dandelion and chickweed in turf, have products designed and ready for commercialization.
In this process, the bacteria or fungal organisms are mass-produced using either a submerged liquid fermentation or solid-substrate (microbes produced on a solid food source) fermentation process. Fermentation processes can be highly specific to a bio-pesticide organism, and are often developed in a custom designed medium. The process involves monitoring dissolved oxygen, pH and propagule (reproductive spore cells) production. For commercialization, it will be imperative to scale up production to a level where it is economically feasible.
Formulation and Application Technology
Formulations create an end product by blending the microbial component with carriers and adjuvants for better protection from unfavourable environments, enhanced survival of the bio-agent, controlled rates of release, as well as improved bioactivity, shelf life, and stability. In order to have effective results on pests such as weeds, it is important to extend leaf wetness. Currently, work is being conducted to enhance spray retention, select droplet size and deposition on the leaf that are most favourable to the efficacy of the agents.
Integrated Pest Management (IPM)
Managers need to know that there is no magic cure when it comes to pest management. However, by using several integrated methods to combat pests, the overall results are often more desirable than using single methods.
An integration model consists of the following:
Bio-pesticide Innovation Chain (Research and Development Model)
When designing bio-herbicides, researchers try to develop broad spectrum products that can control more than one species of pest. The bio-pesticide must also be safe to crops grown in the same environment. Physiological description, fermentation and nutritional factors also play a part in designing bio-herbicides.
Effects of Sugars
The effect sugar has on bacteria and fungi will determine the effectiveness it has on survival, and how well it retains its efficacy when stored for extended periods of time. Manufacturing strategies look at wetting, re-hydration, and disintegration qualities of the product. The product must also conform to a specific size in order that it might be properly applied through various agricultural implements.
Pesta Granules have been developed which include these constituents: rice flour, semolina, oat flour, maltose and specific clay particles. Other additives such as glucose, molasses, peat, skim milk, whey protein, concentrated glycerol, soluble starch and peptone, are also part of the formulation.
Preparing the granules is completed using a bench top granulator (BG), and Twin Screw Extruder (TS). The survival time for bacteria is a quality control measure.
Research, support, and registration
Scientists at AAFC Saskatoon have prepared two products for use on grassy weeds: specifically targeting green foxtail and wild oat. Wild oat and green foxtail are arguably two of the most destructive pests affecting crops grown in western Canada.
A Pesta-formulated soil bacteria; bacterial strain BRG100 is designed to combat green foxtail. A peat prill formulation, bacterial strain 0Y3W011 is designed to combat wild oat.
Because these are living organisms, they are highly dependant on environmental conditions. The agent used to create BRG100 is Pseudomonas fluorescens, which is a naturally occurring soil bacterium that attacks green foxtail.
The fate of BRG100 upon application depends on proper timing, proper rate of application, competition from native soil microbes and crop competitiveness. All these factors together form a synergistic approach to effective weed control.
Mass Production of fungal biocontrol agents
Some foliar applied biocontrol agents that have been developed already include:
Mass production techniques include such things as solid substrate fermentation; submerged liquid fermentation; and a two phased system. Solid substrate fermentation has better aeration, but potentially more contamination of product with undesirable organisms. Submerged liquid fermentation produces a uniform cell culture, but oxygen supply must be maintained. In the two phased system, bio-agent mass is produced in a liquid culture and sporulation (production of spores or reproductive cells) occurs in a solid phase.
Carbon (sugar or other energy source) concentration has a direct impact on production efficiency, and impacts the total mass of cells that are produced. Further development is needed for efficiency in larger, scaled up production systems for bio-agents.
Formulation Development for Bio-herbicides
Initially symbiotic systems were developed which included things like Mycorrhizal fungi and nitrogen fixing bacteria. Other early formulations included peat powders and granules and liquid formulations applied at rates of 100,000 microbes/seed.
In order to be effective, a bio-pesticide must control or suppress a pest population with naturally occurring microbes. These or other organisms may be developed and used in additional applications such as bio-fungicides, bio-herbicides, and bio-insecticides.
Strategies to develop post emergent or pre-emergent formulations have been studied. Current
Bio-pesticide formulations include, an active ingredient, a suitable carrier, and added adjuvants. Each of these contribute to the efficacy of bio-pesticides on the target pest, much in the same way that they do in current chemical pesticides.
Formulations must be compatible, stable, and protected (from unfavourable environments), and useable with common handling equipment.
Spraying bio-pesticides on target species requires application equipment that will allow droplets of spray solution to be evenly applied over the plant tissue and contain sufficient quantity of bio-pesticide organisms to provide adequate impact on the target pest. This type of testing is an integral part of the entire system using bio-pesticides.
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