<P> Parasitic plants such as mistletoe and dodder are included in the study of phytopathology . Dodder, for example, is used as a conduit either for the transmission of viruses or virus - like agents from a host plant to a plant that is not typically a host or for an agent that is not graft - transmissible . </P> <Ul> <Li> Cell wall - degrading enzymes: These are used to break down the plant cell wall in order to release the nutrients inside . </Li> <Li> Toxins: These can be non-host - specific, which damage all plants, or host - specific, which cause damage only on a host plant . </Li> <Li> Effector proteins: These can be secreted into the extracellular environment or directly into the host cell, often via the Type three secretion system . Some effectors are known to suppress host defense processes . This can include: reducing the plants internal signaling mechanisms or reduction of phytochemicals production . Bacteria, fungus and oomycetes are known for this function . </Li> </Ul> <Li> Cell wall - degrading enzymes: These are used to break down the plant cell wall in order to release the nutrients inside . </Li> <Li> Toxins: These can be non-host - specific, which damage all plants, or host - specific, which cause damage only on a host plant . </Li>

Effect of plant pathology on food production and quality of life