An agent that carries a pathogen. Strictly this includes wind, rainsplash, infected tools, etc. but more usually the term is applied to animal vectors and in particular to insects. Man can also be a vector - for example, a scientist examining an outbreak of disease may carry fungal spores on his clothing when moving to a healthy field. Insects are particularly important in the transmission of *virus
and mycoplasma diseases, the most common vectors being aphids, whiteflies, and leafhoppers. The insects acquire the pathogen while feeding on infected plants and transmit it when they move on to a healthy plant. Mites and nematodes are also vectors of virus diseases.