CBSE · Class 12 · Biology · Microbes in Human WelfareDiscuss the role of microbes as biocontrol agents, giving two suitable examples of how they help manage plant pests and diseases.

Biocontrol refers to the use of biological methods for controlling plant diseases and pests, moving away from toxic chemical pesticides and insecticides that cause environmental pollution and bioaccumulation. Microorganisms, including bacteria, fungi, and viruses, act as exceptional biocontrol agents by naturally suppressing the populations of harmful insect pests and pathogens through predation, parasitism, or competition. \nA prime example of a bacterial biocontrol agent is Bacillus thuringiensis (often referred to as Bt). Spores of this bacterium are available in sachets and are sprayed onto vulnerable crops such as brassicas and fruit trees. When ingested by insect larvae, the bacterial toxin gets activated in their alkaline gut and lyses the midgut epithelial cells, killing the pests while leaving non-target beneficial insects unharmed. Genetic engineering has also integrated Bt toxin genes directly into crop plants like Bt cotton. \nAnother prominent example is the fungus Trichoderma, which free-living species are very common in root ecosystems. Trichoderma species act as effective biocontrol agents against several plant pathogens that cause root rot and wilting diseases. They colonize the root zone, outcompete pathogens for space and nutrients, and directly parasitize pathogenic fungi, thereby protecting crops. \nAdditionally, Nucleopolyhedroviruses (NPV) are excellent viral biocontrol agents used to attack specific insect pests and arthropods. They are species-specific, narrow-spectrum insecticides that do not affect mammals, birds, fish, or non-target beneficial insects, making them ideal components of Integrated Pest Management (IPM) programs in sustainable agriculture.