Fungal biocontrol

How do fungi "help control diseases" (from slide 21)?

Hi Spencer Fungi are used in sustainable agriculture largely as bioinsecticides (i.e. for insect control). The fungi have the ability to penetrate the insect cuticle; i.e. as the fungi are pathogenic to insects they can (and are) used as biocontrol agents.
However Spencer (and colleagues) when studying for the midterm exam, I would recommend focusing on the main roles of organisms. In the case of fungi, understanding that they are heterotrophic (i.e. decomposers), some are pathogens (e.g. white rot and brown rot) and that mycorrhizal fungi form symbiotic relationships with plants given those plants an advantage through enhanced nutrient uptake. You may wish to review the three main types of mycorrizal fungi described in lecture 22.