The Relation Between the Size of Plant and the Spread of Systemic Diseases

Abstract

It is an implication of systemic infection by the aphis-borne viruses that potato plants withlarge haulms should be specially vulnerable to infection, and this implication is supported by evidence in the field.Haulms are reduced in size by short days, low temperatures, under-nutrition and varietal differences. Certain observations are adduced to show that these factors reduce vulnerability. It is suggested that the transference of the potato from the short days, infertile soils and primitive cultivation on the Andes to the long summer days and productive farming of Europe and North America enhanced its vulnerability to aphis-borne virus diseases: the further effects of changes of temperature and manurial practices in the last century need elucidation.

The effect of plant spacing, nitrogen fertilizer and irrigation on the appearance of symptoms and spread of virus yellows in sugar-beet crops

“…winged aphids were landing on the taller plants. Not only has a larger plant a greater chance of being colonized by an infective aphid but it also supplies a greater volume of infected plant material from which spread to other plants can occur than a smaller one (van der Plank, 1947). Conditions of maximum susceptibility to virus infection approximate closely to those producing optimum plant growth (Bawden & Kassanis, 1950).…”

Low‐density barriers for controlling plant crowd diseases: How far and fast can pathogens spread?

“…In other words, it is plausible to assume that the farther the individuals are from the source of an infection, the lesser the chances for those individuals to become infected. In the context of plant pathology, this idea was exploited by van der Plank () who defined “plant crowd diseases” as those that neither spread far in considerable amount nor persist long in the soil. Van der Plank presented heuristic arguments to explore how crowd diseases spread and the effects of varying field size as a control method.…”