Potentials of Biocontrol Agents in Disease Management

Biocontrol agents are cultured living microbial products used to combat other living pathogenic organisms. Biocontrol agents are used to suppress the growth or reduce the population of another organism to a level at which it is no longer an economic problem. The activities of biocontrol agents could be likened to probiotics used in animal and poultry disease management. The biocontrol agents provide protection against plant diseases either by direct action against the pathogens and/or indirectly by reducing host susceptibility towards the pathogenic fungi, bacteria, nematodes, protozoa, viruses and seed plants.

The introduction of biocontrol agents for disease management has been one of the major breakthroughs in plant pathology. A large portion of biocontrol agents formulated from fungi (Trichoderma viride, Beauveria bassiana, Paecilomyces lilacinus etc.) or bacteria (Pseudomonas fluorescens, Bacillus subtilis etc.) have been used to control diseases in Greenhouses, Open field cultivations, Seedlings and nurseries. They have been used as preventative measure and/or in combination or alternating with compatible pesticides for effective management of diseases.

Presently, biocontrol agents represent about 1.5 – 2% of the world pesticide market, however, the growth of biocontrol agents over the next ten years has been projected to be 10-15% annually. Biocontrol agents include Biofungicides, Bioinsecticides, Bionematicides, Bioviricides and Biobactericides.

Over time, synthetic chemical pesticides have been reported to produce toxic fumes which are hazardous to farm workers; the effect is greater if used in protected cultivation like greenhouse. The resultant effects from improper usage and handling of synthetic chemical pesticides on health and environment are becoming worrisome. Most synthetic chemical pesticides require a re-entry period before farm workers can return to treated crops and there is a harvest interval, i.e. a period of time between the last application and harvest. Synthetic chemical pesticides have longer residual activity on crops; moreover, their intensive use and limited choice have caused pathogens to develop resistance.

By and large, biocontrol agents have the potential to properly manage pathogenic organisms and diseases. Biocontrol agents are less toxic, cost effective and more stable if stored properly. They have lower re-entry period and safer to use in protected and open field cultivations. Moreover, they have lesser risk of developing resistance to pathogens and good choice for organic and export oriented produces. They are equally good choice for integrated pests management.

For example;

Trichoderma viride and Pseudomonas fluorescens have been effective against damping off, root knot nematode and fusarium wilt that affect tomato, capsicum, cucumber and other crops. Equally, Bacillus subtilis is helpful in managing downy mildew, powdery mildew and fruit rot that affect capsicum, cucumber and tomato. They are used for seeds treatment, drenching seedlings roots and in foliar spray. Beauveria bassiana is effective in managing worms, larvae and other soft-bodied insects. Paecilomyces lilacinus controls nematodes.

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