According to the NCERT text, Trichoderma species are free-living fungi very common in root ecosystems that are effective biocontrol agents of several plant pathogens. In contrast, the Ladybird beetle is an insect (not a microbe) used to control aphids. Nucleopolyhedrovirus attacks insects and other arthropods, not plant diseases like white rust (which is fungal). Bt-cotton is a genetically modified crop, whereas Trichoderma represents the direct use of a microbe as a biocontrol agent.