It Can Be Detrimental, But Is Seldom Fatal
by Bob Bauer
Rose Mosaic Virus (RMV), produces leaves on the plant with patterned yellow to whitish lines or spots in the leaves. This is called "Line Banding". Tne lines appear in a fern like zig zaggy pattern. Leaves can also have a numerous amount of yellow spots reminiscent of mosaic tiles. This is called "Mosaic", and is what give the affliction it's name/ "Watermarking" is another thing to look for. It consists of faint, often nearly invisible swirls and squiggles, in the green color of the leaf. "Vein Banding" is yet another visual effect. It looks like the reverse of iron deficiency, that is the veins are yellow and the leaf is green.
Other symptoms according to Malcolm M. Manners: "Studies in Great Britain and California have demonstrated reduced production of flowers, shorter flower stems, reduced plant vigor, poorer survival when transplanted, poorer cold hardiness, and greater difficulty for nurseries in producing a #1 grade bush. Studies at Florida Southern College also demonstrated the production of fewer flowers, on shorter stems, and reduced longevity." Make sure that you don't confuse RMV with other afflictions that cause leaf yellowing, such as injury by thrips or various nutritional deficiencies caused by lack of certain minerals.
For more information on Rose Mosaic Virus go here: Rose Mosaic Disease Q and A
Rose Problems Page
Since the disease has been proved to not be contagious, there is no great need to remove the bush from your garden. However, if you can be assured to get virus free varieties, they will most likely be more vigorous and bloom more in your garden. So if you have a favorite rose that you would like to see bloom more that is virused, you should replace it. If the virus symptoms are present even on one single leaf, you can be assured that the entire plant is affected. So don't bother pruning off canes with infected leaves, this is pointless. All of this being said, an individual plant CAN be cured by using Heat Therapy. However, this is not something that you can do at home, so don't try it. Make an effort to buy only non virused plants. These are called indexed plants. Indexing is any test that checks for the presence of RMV.
'Designer's Choice'
It is not clear where and when Rose Mosaic Virus came into being, but it is unknown prior to 1920. This is about when the rose Dr. Huey began to be used industry wide in the USA as a commercial root stock on which other hybrid varieties were budded. People have theorized that it was introduced by grafting some wood from a peach or apple tree onto a rose. This bud would not take, but would be enough to infect the rose with the virus. The rose was then eventually budded onto some rootstock which got the virus and the rootstock wood was used to produce future generations of rootstock, which then introduced it into the whole rose world. It appears that NO roses are immune to this problem. The symptoms appear to be worse on some varieties than others, but any rose is capable of getting RMV.
'Lagerfeld'
It is estimated by some that about 50 percent of all roses grown in the USA have rose mosaic virus. These numbers were up to as high as 90 percent in the 1970's. All current evidence has shown that it is spread ONLY by vegetative propagation. That is one infected bush is grafted on and uninfected root stock, or wood from root stock plants is rooted and the infection is spread to plants when they are budded. So there is only one culprit, and that is the nurseries that bud roses. Unfortunately for us, there are a number of commercial rose growers (several in Texas and Arizona and a few in California) who are not willing to actively fight this problem. The fact is they just don't care. Once it leaves their premises and is sold, it is somebody else's problem as far as they are concerned.
That said, there are many responsible growers who care a lot and are doing much to eliminate the problem. The Foundation Plant Materials Service (FPMS) at UC Davis, has a program of producing virus free indexed scions and root stock for about 400 of the most popular rose varieties. Rose growers claim that it would cost too much to clean up their virus problems, but this is certainly not the case in the long run since they would be able to produce more #1 plant and have a more vigorous crop overall to sell to the premium market if they were to fix the problem. The real reason that these growers don't fix the problem, is because of momentum, they have always done thing this way, and that is that. That being said, there are some varieties of roses at this point that aren't available as unvirused varieties. More needs to be done to recover some of these heirloom plants in order to bring them back to their original levels of vigor.
Whereas this can be a partial answer, an own root rose can still be virused if the rooted cutting comes from a plant that is already virused. Nurseries such as Jackson and Perkins and several smaller growers and boutique houses are seriously taking on the problem, but it is a big problem, and it will not be solved for quite some time. It is up to you as the consumer to ask the question of you rose supplier: "Are these roses virus indexed roses?". Make them find out and don't buy them if they are not. This is the real pressure that will change the industry.