Vectors are organisms that can introduce a pathogen
such as a bacterium or virus into a plant to cause an
infection. Insects, mites, and nematode vectors focus
the movement of plant pathogens among immobile
plants. Many insects or other arthropods may contain
plant pathogens but cannot transmit these to plants
and thus are not vectors. Some of our most important
plant diseases require mobile vectors. Almost all plant
viruses and all wall-free, plant pathogenic bacteria
known as mollicutes have recognized or suspected
vectors. See elsewhere for insect vector transmission
of bacterial plant pathogens