by Dr. S. Nameth
OSU Department of Plant Pathology
See the pictures at the end of this article.
Much has been written about the destructive potential of impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV) on bedding plants and herbaceous perennials. This would give one the false impression that these are the only two viruses that cause diseases of floral crops. That is definitely not the case.
Cucumber mosaic virus (CMV) has the widest host range of any plant virus and is a common problem in a wide variety of bedding and perennial plants. The virus infects hundreds of plant families in virtually every continent of the world. The virus is transmitted by a variety of aphid species and aphid transmission is its primary method of moving the virus from plant to plant. It can also be spread by infected seed (in selected hosts) as well as by mechanical transmission ( plant touching plant or propagation tool to plant), but both of these modes of transmission are negligible when compared to aphids. Damage caused by CMV is dependent on the host and the age at which it is infected. In some hosts such as Delphinium sp., CMV infection can cause severe stunting and deformation, while in a host such as geranium the virus has little to no effect on the outward appearance of the plant (See Figures). The older the host the less likely CMV infection will be problem. Plants infected in the early stages of growth and development can be severely stunted, and in some cases plants will die.
Diagnosis of CMV
The most common symptoms associated with CMV infection include mild to severe leaf mosaic, leaf distortion, flower color break, overall plant stunting, and yellowing. (See Figures) In some cases plants infected with CMV can appear to look healthy and may, depending on the environmental conditions grow in and out of symptoms. However, once a plant is infected, its infected for life, symptoms or not.
Controls and Disease Management
The best way to control the disease incited by CMV infection is to avoid virus infection to begin with. This means making sure that the seed or the propagation stock that you purchase is certified disease - or virus - free. Since the virus is transmitted by aphids, the population of these insects in the greenhouse must be keep to a minimum. Also weeds growing outside of the greenhouse can harbor the virus, and aphids can move the virus from these weeds to plants in the greenhouse. If a plant is suspected to have CMV the plant should be removed from the greenhouse and destroyed. Most university and private testing laboratories can test plants fro CMV infection.
.
