There are basically three types of virus that affect cannas and these are: Bean Yellow mosaic virus, Yellow mottle virus, and Yellow streak virus.
These diseases can appear at any time during the growing season.
Bean mottle virus causes a yellow mottling of the leaves.
Yellow mottle virus causes streaks of pale tissue between the leaf veins.
This results in streaks of dead brown tissue as the leaf dies.
Yellow streak virus reacts in a similar manner to yellow mottle virus.
Other symptoms can be; stunted or distorted leaves and or white streaks in the flowers.
Severity is increased when more than one variety of virus is present.
It is not known how this virus is transmitted, but it can be spread in vegetatively propagated plants.
To reduce this possibility strict hygiene procedures should be adopted.
Clean cutting tools after the propagating material has been removed from each plant to prevent contamination being transmitted from plant to plant.
To minimize contracting this virus, care should be taken to ensure you don’t buy infected plants.
This may prove difficult with plant varieties that have natural variegated foliage.
If the disease is found destroy the affected plants.
Apply insecticides to kill off any sap sucking insects that may appear on the plants to prevent them transmitting the disease to other plants.