Sucking and chewing insects carry many viral diseases of potatoes. For example, aphids transmit potato
leaf roll and mosaic viruses from plant to plant. Aphids become infected with the virus while feeding on
diseased plants and are capable of transmitting the virus to healthy seed plants. Attempts to control aphids
in the seed fields may fail to prevent disease introduction. A virus-infected aphid may feed on a potato
plant leaf and introduce the virus into the plant before it succumbs to an insecticide; however, insecticides
do prevent disease transmission from continuing unchecked.