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Canna Diseases

Cannas are susceptible to several plant viruses

By: Sandy Feather ©2008
Penn State Extension


Q. 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 about it?

A. 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.).


Canna Disease Symptoms

CaYMV 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 viruses.

Cannas
Cannas with colorful foliage

 


Viruses and Infected Cannas

Viruses are 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
Canna flowers aren't just red anymore!

Viruses are 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.


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