I have been hearing about a virus that affects
cannas. I have a pretty good collection of some of the fancy-leaved canna varieties that I would hate
to lose. How can I tell if mine have the virus, and if so, what can I do
A number of
different viruses have shown up in cannas in the last few years. Canna Mosaic Virus (CMV) and Canna Yellow Mottle Virus (CaYMV) have
been considered the most important. CMV causes the area between leaf
veins to turn yellow; these areas eventually turn brown and die. It
can also cause stunting and eventual death of infected plants. CMV
is also known as bean yellow mosaic virus and it can infect
gladiolus (Gladiolus spp.), lupines (Lupinus spp.), flowering
tobacco (Nicotiana spp.), and petunias (Petunia spp.).
symptoms include yellowing of veins, yellow or brown spots on the
leaves, or a distinct mottling on the leaves. White streaks in the
flower petals (known as color breaking) are another symptom of both
|Cannas with colorful foliage
Viruses and Infected Cannas
systemic, so infected plants should be dug up and thrown away; there
is no chemical control for plant diseases caused by viruses. Canna
rhizomes that are infected with virus should be buried (in an area
where you will not plant cannas in the near future) or burned.
Dividing infected rhizomes can spread both viruses. CMV can also be
transmitted by aphids, but insects have not been identified as
vectors for CaYMV. If you are shopping for cannas, ask for rhizomes
that have been tested and found to be virus free.
CMV Disease Identification
A definitive identification of
viral infection requires laboratory analysis. Many university
disease diagnostic laboratories do not perform virus indexing,
including Penn State’s. Testing is available through the University
of Minnesota. Fees vary depending on the test, with a $37.00 minimum.
|Canna flowers aren't
just red anymore!
often transmitted by propagation from cuttings, on tools, or by
human contact with infected plants then moving to a healthy plant.
Wildlife can also spread diseases by getting infected sap in their
claws, fur or feathers, and beaks or teeth, then moving on to a
healthy plant. Most viruses require live tissue to survive and do
not persist in the soil as long as ALL infected canna roots and
pieces have been removed from the planting area. Since cannas are
not considered winter hardy in our climate, those pieces will be
long dead by spring.
Black spot on roses
Azalea Bark Scale