Once unheard-of in the horticultural world, the canna virus began to infect and harm cannas in gardens around the year 2000. Today, the canna virus is an issue worldwide since the canna plant nursery growing areas of the Netherlands, France, the United States, Israel, and Australia have identified the problem. Plants suffering from canna virus lack vigor and fail to produce food in their leaves, causing the root rhizomes to succumb to winter cold, drought or other factors. No treatment is available for canna virus, and infected plants should be destroyed.
The first hints of a canna plant plagued by a plant virus are pale, tiny speckles on the leaves. On green-leaf varieties that mean specks that are lighter green to yellow, whereas bronze-, red- and purple-leaf plants have pink-beige to white flecks. In variegated plants, such as those with naturally streaking leaves of green, yellow and pink, it is very easy to overlook the speckling.
Streaking occurs just after or alongside the initial speckling on canna leaves. At first the streaks are short and only occur parallel to the leaf veins. As with speckling, variegated leaves that have natural yellow and green stripes may be difficult to examine since the viral streaking is similar. Once the virus deepens, the streaks become dead and leave a dry, tan streak among living leaf tissue.
Abnormally Formed Leaves
In severely infested plants, even the younger emerging leaves on stems and popping up from the ground will be heavily distorted and twisted. The excessive streaking and dry bands of tissues in the infected leaves causes the leaf blades to curl, ripple or look corrugated. Moreover, the leaf is much yellower than usual, if a green-leaf canna, or paler in color, if naturally bronze-, red- or purple-leafed.