EXPERIMENTS ON THE COLONIZATION OF POTATO PLANTS BY APTEROUS AND BY ALATE APHIDS IN RELATION TO THE SPREAD OF VIRUS DISEASES

Batches of potato plants in pots were placed in the field for limited periods among plants infected with potato virus Y and leaf roll virus. Some of the potted plants were surrounded by sticky boards which prevented apterous aphids from reaching them. Almost as many plants within the boards as without became infected, indicating that most of the spread of virus was by winged aphids.
Apterae were probably responsible for spreading the viruses throughout a hill after one or more stems were infected. They may carry infection to neighbouring plants, but most of these will have been infected already by alatae.
The number of plants contracting infection was unaffected by watering.