De bladrolziekte van de aardappelplant

Macroscopic and microscopic symptoms of leaf-roll disease of potatoes were extensively discussed in an analysis of the cause. Infected plants, derived from healthy tubers, frequently showed no symptoms during growth. Sometimes signs of discolouring and of rolling could be detected, first in the uppermost leaves, but they were not distinctive for this disease. If the seed potato was already infected, leaves, first the lowest, hardened and rolled about 30 days after the plant came up. This was preceded by a disturbance of starch breakdown. After the external symptoms necrosis of the phloem always developed and was specific. Information on the abnormal action of certain enzymes in diseased plants was reviewed.The disease was contagious during growth. Transfer was by lice and probably also bugs. Another possibility was transfer within the soil. The rapidity of spread depended largely on still unknown environmental conditions. Control was sought first in the possibility of breeding less susceptible varieties, as there were great differences in susceptibility.