Biotrophs are pathogens that derive nutrients from living host tissues, and necrotrophs
are pathogens that derive nutrients from dead or dying cells (4). Some
pathogens can be clearly assigned as biotrophs or necrotrophs. However, many
others behave as both biotrophs and necrotrophs, depending on the conditions
in which they find themselves or the stages of their life cycles. Such pathogens are called hemi-biotrophs. Many fungi that are commonly considered necrotrophs
may really be hemi-biotrophs, as they have a biotrophic stage early in the infection
process.